14 May
2008
14 May
'08
2:46 p.m.
Hi folks,
I just dug my old Osborne OCC1 (1st model, in the beige vacuum-formed ABS
case), only to find all is not well. Actually, "finding" all is not well is
a bit of a white lie - I already knew it was in trouble, from when I last
tried to boot it about 2 years ago...
Unfortunately, the intervening 2 years have failed to fix the problem, which
is that the video seems to have no horizontal hold.
It took a few goes, but eventually it booted from a CP/M disk; with
scrambled video. The links below are to a picture & two versions of the same
video (16 seconds of special-effects laden trickery...):
PIC: The startup screen in scrambled fashion:
http://www.solutionengineer.com/ozzie/occ1_prb.jpg
VID: Booting to CP/M:
MOV format (4mb): http://www.solutionengineer.com/ozzie/occ1_prb.mov
MPEG2 format (9mb):
http://www.solutionengineer.com/ozzie/occ1_prb.mpg
Please excuse the camera wobble on the movie... The constant high-pitch
whine is, I think, the image stabiliser in my camera working away.
Now.... If I pull the termination block off the External Video connector,
the screen goes out (as one would expect); push it back on & the screen
comes back on with the display as steady as a rock -- unfortunately, it's
crashed the computer... From this, I deduce that it must be something in the
mainboard electronics that's failed (a cap, maybe?), rather than something
in the monitor unit.
Any ideas where to start looking? I have an oscilloscope (albeit I've
forgotten how to use it, and am not 100% sure where the probes are), and a
multimeter... beyond that, not a lot.
I've tried cleaning the contacts to the monitor, and around the Ext Vid.
termination block; and I've wiggled the three cable connectors to the
mainboard a few times to clean them up. I've also popped each of the three
socketed chips in & out a couple of time to clean the legs up. Finally, I
soldered the contrast knob back together - one of the legs had broken.
Basically, everything works except for the shaky video. Sometimes you see a
whole page full of 1s, or 0s; essentially, it's all a bit random. Bad
connection somewhere, perhaps, or maybe a failing chip?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1431 - Release Date: 13/05/2008
19:55
14 May
14 May
3:23 p.m.
Ade,
I don't know the internals of the Osborne but can help you with some repair
rules of thump .
First step, is checking the boards visual for corosion and bad solder joints
(crystaline with a round marking in the solder) good joints are shiny and
curved, if you don't trust one remove the old solder and resolder.
And of cause scheck the board for burned and broken components
Second step, is to locate the power supply and check the voltages with a
multimeter, after that you check them with the scope for ripple and spikes.
Typical PSU should have no more then 100-300mV ripple spikes and noise.
If there is a lot of noise or spikes check the decoupling Elco's and
tantalium C's if you have a lot of ripple that indicates a bad ripple elco
in the PSU.
Sometimes placing a few 200nF C's over the +5V rejects a lot of noise and
will give you a good indication were to look (decoupling C's)
Third, check components for heat development, heated components indicates
shortcuts.
When old electronics is stowed away in storages for a long time, elcos are
going to degrade and eventualy won't work at all.
The picture your showing indicates a fault in the horizontal sync circuit
of the video, pausible cause degraded elco's.
This also can be the cause at a bad startup due to a short reset time, witch
would be caused by a elco with a too low capacity.
Rik
----- Original Message -----
From: "Ade Vickers" <javickers at solutionengineers.com>
To: "CCTalk" <cctalk at classiccmp.org>
Sent: Wednesday, May 14, 2008 8:46 PM
Subject: Osbourne OCC1 problem
Hi folks,
I just dug my old Osborne OCC1 (1st model, in the beige vacuum-formed ABS
case), only to find all is not well. Actually, "finding" all is not well
is
a bit of a white lie - I already knew it was in trouble, from when I last
tried to boot it about 2 years ago...
Unfortunately, the intervening 2 years have failed to fix the problem,
which
is that the video seems to have no horizontal hold.
It took a few goes, but eventually it booted from a CP/M disk; with
scrambled video. The links below are to a picture & two versions of the
same
video (16 seconds of special-effects laden trickery...):
PIC: The startup screen in scrambled fashion:
http://www.solutionengineer.com/ozzie/occ1_prb.jpg
VID: Booting to CP/M:
MOV format (4mb): http://www.solutionengineer.com/ozzie/occ1_prb.mov
MPEG2 format (9mb):
http://www.solutionengineer.com/ozzie/occ1_prb.mpg
Please excuse the camera wobble on the movie... The constant high-pitch
whine is, I think, the image stabiliser in my camera working away.
Now.... If I pull the termination block off the External Video connector,
the screen goes out (as one would expect); push it back on & the screen
comes back on with the display as steady as a rock -- unfortunately, it's
crashed the computer... From this, I deduce that it must be something in
the
mainboard electronics that's failed (a cap, maybe?), rather than something
in the monitor unit.
Any ideas where to start looking? I have an oscilloscope (albeit I've
forgotten how to use it, and am not 100% sure where the probes are), and a
multimeter... beyond that, not a lot.
I've tried cleaning the contacts to the monitor, and around the Ext Vid.
termination block; and I've wiggled the three cable connectors to the
mainboard a few times to clean them up. I've also popped each of the three
socketed chips in & out a couple of time to clean the legs up. Finally, I
soldered the contrast knob back together - one of the legs had broken.
Basically, everything works except for the shaky video. Sometimes you see
a
whole page full of 1s, or 0s; essentially, it's all a bit random. Bad
connection somewhere, perhaps, or maybe a failing chip?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1431 - Release Date:
13/05/2008
19:55
--------------------------------------------------------------------------------
No virus found in this incoming message.
Checked by AVG.
Version: 8.0.100 / Virus Database: 269.23.16/1432 - Release Date: 14-5-2008
7:49
5:19 p.m.
Hi folks,
I just dug my old Osborne OCC1 (1st model, in the beige vacuum-formed ABS
case), only to find all is not well. Actually, "finding" all is not well is
a bit of a white lie - I already knew it was in trouble, from when I last
tried to boot it about 2 years ago...
Unfortunately, the intervening 2 years have failed to fix the problem, which
is that the video seems to have no horizontal hold.
[...]
Now.... If I pull the termination block off the External Video connector,
the screen goes out (as one would expect); push it back on & the screen
comes back on with the display as steady as a rock -- unfortunately, it's
crashed the computer... From this, I deduce that it must be something in the
mainboard electronics that's failed (a cap, maybe?), rather than something
in the monitor unit.
Now, I don;t know this machine at all, but I am assuming the mainboad
contains the video and sync generation circuitry, while the 'monitor'
contains the deflection circuits that lock to said sync signals, the
video amplifier, HV generator, etc.
Are the signals between the monitor and mainboard separate syncs and
video or a composite video signal?
It is my expeireince that this sort of prolem is caused by a failing
component arouund the horizontal oscillator / PLL / sync circuit. It's
unlikely to be a digial problem. And this is a horizontal problem
(picture breaks up into sloping likes)not a vertical problem (picture
rolls), right?
If you do have seaprate signals to the monitor, start by 'scoping the
horizontal sync signal while the monitor is malfunctioning. Is it the
right frequency and stable?
Then, if there's a horizotnal frequency control on the monitor PCB (it
might be an inductor!), try carefully tweaking it. The idea is to (a) see
if the thing will jump into lock, or if not, at least if you can get it
to slope both ways (that is, can the horizotnal oscillator run above and
elow the right frequency, if so, it's a good bet it'll work _at_ the
right frequency, and that the problem is in the sync circuit).
-tony
6:08 p.m.
It is said to never remove the external video connector with the power on, or you risk
damaging the video circuitry. In what manner, I do not know.
--- On Wed, 5/14/08, Ade Vickers <javickers at solutionengineers.com> wrote:
From: Ade Vickers <javickers at
solutionengineers.com>
Subject: Osbourne OCC1 problem
To: "CCTalk" <cctalk at classiccmp.org>
Date: Wednesday, May 14, 2008, 11:46 AM
Hi folks,
I just dug my old Osborne OCC1 (1st model, in the beige
vacuum-formed ABS
case), only to find all is not well. Actually,
"finding" all is not well is
a bit of a white lie - I already knew it was in trouble,
from when I last
tried to boot it about 2 years ago...
Unfortunately, the intervening 2 years have failed to fix
the problem, which
is that the video seems to have no horizontal hold.
It took a few goes, but eventually it booted from a CP/M
disk; with
scrambled video. The links below are to a picture & two
versions of the same
video (16 seconds of special-effects laden trickery...):
PIC: The startup screen in scrambled fashion:
http://www.solutionengineer.com/ozzie/occ1_prb.jpg
VID: Booting to CP/M:
MOV format (4mb):
http://www.solutionengineer.com/ozzie/occ1_prb.mov
MPEG2 format (9mb):
http://www.solutionengineer.com/ozzie/occ1_prb.mpg
Please excuse the camera wobble on the movie... The
constant high-pitch
whine is, I think, the image stabiliser in my camera
working away.
Now.... If I pull the termination block off the External
Video connector,
the screen goes out (as one would expect); push it back on
& the screen
comes back on with the display as steady as a rock --
unfortunately, it's
crashed the computer... From this, I deduce that it must be
something in the
mainboard electronics that's failed (a cap, maybe?),
rather than something
in the monitor unit.
Any ideas where to start looking? I have an oscilloscope
(albeit I've
forgotten how to use it, and am not 100% sure where the
probes are), and a
multimeter... beyond that, not a lot.
I've tried cleaning the contacts to the monitor, and
around the Ext Vid.
termination block; and I've wiggled the three cable
connectors to the
mainboard a few times to clean them up. I've also
popped each of the three
socketed chips in & out a couple of time to clean the
legs up. Finally, I
soldered the contrast knob back together - one of the legs
had broken.
Basically, everything works except for the shaky video.
Sometimes you see a
whole page full of 1s, or 0s; essentially, it's all a
bit random. Bad
connection somewhere, perhaps, or maybe a failing chip?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1431 - Release
Date: 13/05/2008
19:55
7:12 p.m.
New subject: Osborne OCC1 problem
There's no "u" in Osborne! :-)
On Wednesday 14 May 2008 14:46, Ade Vickers wrote:
Hi folks,
I just dug my old Osborne OCC1 (1st model, in the beige vacuum-formed ABS
case), only to find all is not well. Actually, "finding" all is not well is
a bit of a white lie - I already knew it was in trouble, from when I last
tried to boot it about 2 years ago...
Unfortunately, the intervening 2 years have failed to fix the problem,
which is that the video seems to have no horizontal hold.
It took a few goes, but eventually it booted from a CP/M disk; with
scrambled video. The links below are to a picture & two versions of the
same video (16 seconds of special-effects laden trickery...):
PIC: The startup screen in scrambled fashion:
http://www.solutionengineer.com/ozzie/occ1_prb.jpg
VID: Booting to CP/M:
MOV format (4mb): http://www.solutionengineer.com/ozzie/occ1_prb.mov
MPEG2 format (9mb):
http://www.solutionengineer.com/ozzie/occ1_prb.mpg
Please excuse the camera wobble on the movie... The constant high-pitch
whine is, I think, the image stabiliser in my camera working away.
Now.... If I pull the termination block off the External Video connector,
the screen goes out (as one would expect); push it back on
You mean that connector that on most of the ones I've seen have a sticker on
the front saying not to remove it while the power is on?
& the screen comes back on with the display as
steady as a rock --
Good. What I'd do there is get one of those pencil-shaped ink erasers and rub
the contacts on both sides of the board with that connector off of there,
and then put it back on, and leave it there. If you still have some erratic
operation, you can take little bits of wire-wrap wire and solder them to
both sides, which I had to do in at least one case.
unfortunately, it's crashed the computer... From
this, I deduce that it must
be something in the mainboard electronics that's failed (a cap, maybe?),
rather than something in the monitor unit.
Monitor not getting sync would be a problem all right and if your display
problem went away that easily then maybe just cleaning those contacts up will
fix it right up.
Any ideas where to start looking? I have an
oscilloscope (albeit I've
forgotten how to use it, and am not 100% sure where the probes are), and a
multimeter... beyond that, not a lot.
I've tried cleaning the contacts to the monitor, and around the Ext Vid.
termination block; and I've wiggled the three cable connectors to the
mainboard a few times to clean them up. I've also popped each of the three
socketed chips in & out a couple of time to clean the legs up. Finally, I
soldered the contrast knob back together - one of the legs had broken.
Basically, everything works except for the shaky video. Sometimes you see a
whole page full of 1s, or 0s; essentially, it's all a bit random. Bad
connection somewhere, perhaps, or maybe a failing chip?
Ok, so you're getting solid video or shaky video? I thought you had said
that wiggling the connector fixed that...?
And does this unit have a screen-pac upgrade? If so, it'll have an RCA jack
in one corner of the front panel, you can feed that to a composite-input
monitor. If not we'll have to work on what's there.
I'd have a look at the outputs of the power supply, start out with the unit
off and the power disconnected and _don't_ touch that big power transistor or
it _will_ bite! Stay on the output side and measure what's there. The +5,
and + and -12 should be within 5% of where they're supposed to be,
particularly the +5. Better yet would be to scope them and see how much
trash is there. You might have power supply issues. Or you might have
monitor issues, too. I can recall reading about some monitor problems in
those machines or maybe Execs that turned out to be bad capacitors but I
can't recall which ones and I don't have those issues of Foghorn handy any
more.
I *might* have power supply schematics for that unit, I'll have to look.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
15 May
15 May
4:13 a.m.
New subject: Osborne OCC1 problem
Hi chaps,
This is a kind of amalgamated response to all who have responded; thanks!
Roy J. Tellason wrote:
There's no "u" in Osborne! :-)
Doh! Quite right.... I must have been watching too many Bourne films...
You mean that connector that on most of the ones I've seen
have a sticker on the front saying not to remove it while the
power is on?
No such sticker on mine, so I can claim ignorance...
Good. What I'd do there is get one of those
pencil-shaped
ink erasers and rub the contacts on both sides of the board
with that connector off of there, and then put it back on,
and leave it there.
I've already tried all that, using fine wet&dry paper to bring the
connections upto a sparkle, as well as giving the connectors inside the
block a rub down as well. None has made the slightest bit of difference. The
*only* time the video is steady is if the computer has crashed (i.e. because
the ext. vid block has been removed & replaced).
If you still have some erratic
operation, you can take little bits of wire-wrap wire and
solder them to both sides, which I had to do in at least one case.
I'd like to avoid that if I can, but if that's what it takes, that's what
I'll do.
unfortunately,
it's crashed the computer... From this, I
deduce that
it must be something in the mainboard electronics
that's failed (a
cap, maybe?), rather than something in the monitor unit.
Monitor not getting sync would be a problem all right and if
your display problem went away that easily then maybe just
cleaning those contacts up will fix it right up.
Ok, so you're getting solid video or shaky video? I thought
you had said that wiggling the connector fixed that...?
As I say, it only goes away if you can put up with the computer being
completely crashed (a soft-reset won't do the business, it has to be mains
off/mains on to get it restarted; and then the video's loopy again.
In other words:
1) Power up. Video shaky
2) Pull ext. vid block, video goes off
3) Replace block, video returns, stable, computer totally crashed.
4) Power off. Goto 1.
And does this unit have a screen-pac upgrade? If so,
it'll
have an RCA jack in one corner of the front panel, you can
feed that to a composite-input monitor. If not we'll have to
work on what's there.
No, it's standard unmodified. Although the Ext Vid block shows some signs of
damage, like someone's tried to pry it open. I've no idea if that's causing
the problem, although I should point out that this machine worked 3-4 years
ago, and has "gone off" in storage.
I'd have a look at the outputs of the power supply, start
out with the unit off and the power disconnected and _don't_
touch that big power transistor or it _will_ bite!
Fear not! I have a healthy regard for self preservation whilst working
around mains-level circuitry... hv had 3 mains jolts in my life, the last
one made my chest hurt in alarming fashion. That was when I was 13 years
old...
Stay on
the output side and measure what's there. The +5, and + and
-12 should be within 5% of where they're supposed to be,
particularly the +5. Better yet would be to scope them and
see how much trash is there. You might have power supply
issues. Or you might have monitor issues, too. I can
recall reading about some monitor problems in those machines
or maybe Execs that turned out to be bad capacitors but I
can't recall which ones and I don't have those issues of
Foghorn handy any more.
OK, will check that today (the levels), and if I find the 'scope probes,
then I'll see if that still works (been 2-3 years since I used the 'scope,
so that may have died also!)
Tony Duell wrote:
Now, I don;t know this machine at all, but I am
assuming the
mainboad contains the video and sync generation circuitry,
while the 'monitor'
contains the deflection circuits that lock to said sync
signals, the video amplifier, HV generator, etc.
I believe that to be the case. I could take some close-ups of the monitor
circuit if you like. There are a number of trimpots covering vertical
hold/lin/synch, one for the horizontal centering, one each for
bright/contrast. There is only one IC on the monitor circuit board.
Are the signals between the monitor and mainboard
separate
syncs and video or a composite video signal?
I'll have to do some tracing, but I think they are separate V & H. There are
10 wires going from the mainboard to the monitor, but not sure what signals
they carry.
sync circuit. It's unlikely to be a digial
problem. And this
is a horizontal problem (picture breaks up into sloping
likes)not a vertical problem (picture rolls), right?
Hmm; I don't think it is wholly an analogue problem: I would expect the
screen to break into horizontal slopes, as you say - and I've seen that on
badly adjusted monitors in the past (I used to have an old Philips monitor
which could be provoked into this with the front panel adjusters).
What's happening is a corruption of the display, rather than an adjustment
fault. For example, I just booted the machine again, and (ever so briefly)
got an entire screenful of the letter "U". Then it went away, and the
Osborne logo came back (and that *did* show some signs of an analogue issue
- the horizontal slopes; but lots of them, not just a few). There's no way a
horizontal hold failure could cause the screen to be filled with "U"s...
If you do have seaprate signals to the monitor, start
by
'scoping the horizontal sync signal while the monitor is
malfunctioning. Is it the right frequency and stable?
I'll look for it... the monitor circuit board is quite well labeled; but I'm
not sure if the connectors themselves have individually labelled
connections.
Then, if there's a horizotnal frequency control on the
monitor PCB (it might be an inductor!), try carefully
tweaking it. The idea is to (a) see if the thing will jump
into lock, or if not, at least if you can get it to slope
both ways (that is, can the horizotnal oscillator run above
and elow the right frequency, if so, it's a good bet it'll
work _at_ the right frequency, and that the problem is in the
sync circuit).
I couldn't find a h-freq trimpot; but will pull it all out again later today
for a looksee.
Question: How long should I leave the tube to "cool down" (unplugged) before
I can rummage around it without fear of major electrocution?
Rik wrote:
First step, is checking the boards visual for corosion
and
bad solder joints (crystaline with a round marking in the
solder) good joints are shiny and curved, if you don't trust
one remove the old solder and resolder.
I had a quick glance over the board, and didn't see anything really obvious;
will check again properly.
When old electronics is stowed away in storages for a
long
time, elcos are going to degrade and eventualy won't work at all.
The picture your showing indicates a fault in the horizontal
sync circuit of the video, pausible cause degraded elco's.
That kind of figures - except for the fact it will go rock steady when the
external video plug is pulled & replaced - but as mentioned, that freezes
the whole machine solid (soft reset doesn't work, I have to cycle the power
to restart it). I therefore think it must be something interfering with the
h-sync generation while the machine is running which is causing the problem.
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1433 - Release Date: 14/05/2008
16:44
12:22 p.m.
New subject: Osborne OCC1 problem
On Thursday 15 May 2008 04:13, Ade Vickers wrote:
(Snip)
I did that for the case where the plug was missing altogether. Though it
seems to me to be possible to solder the wire on one side of each of those
contacts and still allow the plug to be used...
I wonder if anybody ever sold anything that plugged in there?
As I say, it only goes away if you can put up with the computer being
completely crashed (a soft-reset won't do the business, it has to be mains
off/mains on to get it restarted; and then the video's loopy again.
In other words:
1) Power up. Video shaky
2) Pull ext. vid block, video goes off
3) Replace block, video returns, stable, computer totally crashed.
4) Power off. Goto 1.
Hmm. Might be the load on the power supply then, if it's marginal.
Might be aging caps in there then.
Not fun, for sure...
A scope is a nice thing to have when trying to troubleshoot this sort of
thing, definitely.
The odd characters I noticed in some of the pictorial info you linked to
earlier suggests memory corruption, which would also be power-supply
related.
I'm not sure, but I believe that these monitors might have been made by
Zenith. Or at least I'd heard that to be the case with the one in the Exec.
If you see blobs of hot glue here and there holding down larger components
that's a pretty good giveaway.
I'd worry about both the monitor and the computer getting good clean power
first. Until you get sure about that I wouldn't mess with any adjustments.
That's why I suspect the power supply first. :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
If you still
have some erratic operation, you can take little bits of
wire-wrap wire and solder them to both sides, which I had to do in at
least one case.
I'd like to avoid that if I can, but if that's what it takes, that's what
I'll do. unfortunately, it's crashed the computer... From
this, I deduce that it
must be something in the mainboard electronics that's failed (a cap,
maybe?), rather than something in the monitor unit.
Monitor not getting sync would be a problem all right and if
your display problem went away that easily then maybe just
cleaning those contacts up will fix it right up.
Ok, so you're getting solid video or shaky video? I thought
you had said that wiggling the connector fixed that...? And does this
unit have a screen-pac upgrade? If so, it'll
have an RCA jack in one corner of the front panel, you can
feed that to a composite-input monitor. If not we'll have to
work on what's there.
No, it's standard unmodified. Although the Ext Vid block shows some signs
of damage, like someone's tried to pry it open. I've no idea if that's
causing the problem, although I should point out that this machine worked
3-4 years ago, and has "gone off" in storage. I'd have a
look at the outputs of the power supply, start
out with the unit off and the power disconnected and _don't_
touch that big power transistor or it _will_ bite!
Fear not! I have a healthy regard for self preservation whilst working
around mains-level circuitry... hv had 3 mains jolts in my life, the last
one made my chest hurt in alarming fashion. That was when I was 13 years
old... Stay on the
output side and measure what's there. The +5, and + and
-12 should be within 5% of where they're supposed to be, particularly the
+5. Better yet would be to scope them and see how much trash is there.
You might have power supply issues. Or you might have monitor issues,
too. I can recall reading about some monitor problems in those machines
or maybe Execs that turned out to be bad capacitors but I can't recall
which ones and I don't have those issues of Foghorn handy any more.
OK, will check that today (the levels), and if I find the 'scope probes,
then I'll see if that still works (been 2-3 years since I used the 'scope,
so that may have died also!) Tony Duell wrote:
They are.
Now, I don;t know this machine at all, but I am
assuming the mainboad
contains the video and sync generation circuitry, while the 'monitor'
contains the deflection circuits that lock to said sync signals, the video
amplifier, HV generator, etc.
I believe that to be the case. I could take some close-ups of the monitor
circuit if you like. There are a number of trimpots covering vertical
hold/lin/synch, one for the horizontal centering, one each for
bright/contrast. There is only one IC on the monitor circuit board.
Are the signals between the monitor and mainboard
separate
syncs and video or a composite video signal?
I'll have to do some tracing, but I think they are separate V & H. There are 10 wires going from the mainboard to the
monitor, but not sure
what signals they carry.
Horizontal and vertical sync, video, and power, as far as I can recall.
sync circuit.
It's unlikely to be a digial problem. And this
is a horizontal problem (picture breaks up into sloping
likes)not a vertical problem (picture rolls), right?
Hmm; I don't think it is wholly an analogue problem: I would expect the
screen to break into horizontal slopes, as you say - and I've seen that on
badly adjusted monitors in the past (I used to have an old Philips monitor
which could be provoked into this with the front panel adjusters).
What's happening is a corruption of the display, rather than an adjustment
fault. For example, I just booted the machine again, and (ever so briefly)
got an entire screenful of the letter "U". Then it went away, and the
Osborne logo came back (and that *did* show some signs of an analogue issue
- the horizontal slopes; but lots of them, not just a few). There's no way
a horizontal hold failure could cause the screen to be filled with "U"s...
If you do have
seaprate signals to the monitor, start by 'scoping the
horizontal sync signal while the monitor is malfunctioning. Is it the
right frequency and stable?
I'll look for it... the monitor circuit board is quite well labeled; but
I'm not sure if the connectors themselves have individually labelled
connections. Then, if
there's a horizotnal frequency control on the monitor PCB (it
might be an inductor!), try carefully tweaking it. The idea is to (a) see
if the thing will jump into lock, or if not, at least if you can get it to
slope both ways (that is, can the horizotnal oscillator run above
and elow the right frequency, if so, it's a good bet it'll work _at_ the
right frequency, and that the problem is in the sync circuit).
I couldn't find a h-freq trimpot; but will pull it all out again later
today for a looksee. Question: How long should I leave the tube to
"cool down" (unplugged)
before I can rummage around it without fear of major electrocution?
The HV wire in there is going to be pretty obviously going to one side of the
tube, as opposed to the rest of the connections which will go to the tube's
base (small end of the "funnel") or the deflection yoke. Just staying away
from that should be good enough.
Rik wrote:
A strong light helps with that but I haven't found too much in the way of bad
soldering in this equipment.
First step, is checking the boards visual for
corosion and
bad solder joints (crystaline with a round marking in the
solder) good joints are shiny and curved, if you don't trust
one remove the old solder and resolder.
I had a quick glance over the board, and didn't see anything really
obvious; will check again properly. When old
electronics is stowed away in storages for a long
time, elcos are going to degrade and eventualy won't work at all.
The picture your showing indicates a fault in the horizontal
sync circuit of the video, pausible cause degraded elco's.
That kind of figures - except for the fact it will go rock steady when the
external video plug is pulled & replaced - but as mentioned, that freezes
the whole machine solid (soft reset doesn't work, I have to cycle the power
to restart it). I therefore think it must be something interfering with the
h-sync generation while the machine is running which is causing the
problem.
12:40 p.m.
New subject: Osborne OCC1 problem
Roy J. Tellason wrote:
<loads snipped temporarily>
A scope is a nice thing to have when trying to troubleshoot
this sort of thing, definitely.
It's going to have to be the 'scope... I failed to turn the multimeter off
properly last time I used it, and now the battery is flat. Doh!
Or, of course, I could bodge my universal power supply into powering the
multimeter...... (don't dare suggest buying a battery! ;))
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1433 - Release Date: 14/05/2008
16:44
2:38 p.m.
New subject: Osborne OCC1 problem
Hmmm....
OK, stranger & stranger.
The power supply has 3 identical "plugs" (for want of a better word) coming
off the board, each with 4 pins. The voltage on each corresponding pin of
each plug is identical; so I'm assuming they're there to power other
optional (and presumably never built) kit. Anyhoo...
Without my voltmeter, I've done my best to calibrate the 'scope (which I've
never used in anger before) to a sensible scale. From this scale I have
concluded that, with respect to GND:
Pin 1 has approx -13.5v - but is not connected to anything
Pin 2 has approx +12.0v
Pin 3 has approx - 0.1v (and is a bit rough, but only on the millivolt
scale)
Pin 4 has approx + 4.5v (higher, actually, somewhere between 4.5v and 5.0v
All three signals are pretty smooth, I can't see any rectification noise on
them until I get into the millivolt scales - even as far down as I can
adjust the 'scope.
The crystal is working properly :)
I've not checked the voltages going into the monitor yet - I need to do some
additional dissasembly so I can get the probe in, and it's knocking off
time...
However, the PSU looks good, I'd say.
The display is still fritzed :(
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1433 - Release Date: 14/05/2008
16:44
3:19 p.m.
New subject: Osborne OCC1 problem
On Thursday 15 May 2008 14:38, Ade Vickers wrote:
Hmmm....
OK, stranger & stranger.
The power supply has 3 identical "plugs" (for want of a better word) coming
off the board, each with 4 pins. The voltage on each corresponding pin of
each plug is identical; so I'm assuming they're there to power other
optional (and presumably never built) kit. Anyhoo...
Without my voltmeter, I've done my best to calibrate the 'scope (which I've
never used in anger before) to a sensible scale. From this scale I have
concluded that, with respect to GND:
Pin 1 has approx -13.5v - but is not connected to anything
That's the nominal -12V, and it's used in the RS232 port and nowhere else
that I can recall.
Pin 2 has approx +12.0v
That's the nominal +12, and is used in the RS232 port and the disk drives.
Pin 3 has approx - 0.1v (and is a bit rough, but only
on the millivolt
scale)
Measured with respect to where? That's probably your ground pin.
Pin 4 has approx + 4.5v (higher, actually, somewhere
between 4.5v and 5.0v
That should be +5 give or take a quarter volt and no more, if it goes down to
as low as 4.5V you have a bit of a problem there, which could account for
some of the erratic behavior you're seieng.
All three signals are pretty smooth, I can't see
any rectification noise on
them until I get into the millivolt scales - even as far down as I can
adjust the 'scope.
That's good to know.
The crystal is working properly :)
I've not checked the voltages going into the monitor yet - I need to do
some additional dissasembly so I can get the probe in, and it's knocking
off time...
However, the PSU looks good, I'd say.
Except for that one reading that's somewhat rather lower than I'd like to see.
The display is still fritzed :(
No surprise there. :-)
Is there a trimpot adjustment on that power supply board? I used to work on
those machines (we had "the shop" in a building that had an Osborne dealer in
it so I saw more of those than any other CP/M boxes) but it's been rather a
while since I saw one. I just looked in one set of files and can't seem to
find any schematics or other stuff, though I know I have one somewhere, so
I guess I'm working from memory here.
You might locate the biggest caps on that power supply board (they'll have the
highest voltage rating and be on the primary side of things, probably two of
them) and give some consideration to replacing those.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
3:32 p.m.
New subject: Osborne OCC1 problem
Roy J. Tellason wrote:
OK. I'm not sure how it gets there, as there is no connection in the plug to
take it (and there's only the single 3-wire plug leaving the PSU board...
Yep, figured that one.
Measured with respect to Earth (green wire, goes everywhere including to the
mainboard). As far as I can tell, this acts as GND for the whole machine?
Well..... as my multimeter is flat & I don't have a signal generator, I
calibrated the 'scope using a 1.5v AA battery. Thus, accuracy is far from
guaranteed...
As I say, it IS a little higher than 4.5v - it may be 4.75, but I couldn't
be sure of that. I will find a new battery for the multimeter tonight...
I have
concluded that, with respect to GND:
Pin 1 has approx -13.5v - but is not connected to anything
That's the nominal -12V, and it's used in the RS232 port and
nowhere else that I can recall. Pin 2 has approx +12.0v
That's the nominal +12, and is used in the RS232 port and
the disk drives. Pin 3 has approx - 0.1v (and is a bit rough, but
only on
the millivolt
scale)
Measured with respect to where? That's probably your ground pin. Pin 4 has approx + 4.5v (higher, actually,
somewhere
between 4.5v and
5.0v
That should be +5 give or take a quarter volt and no more,
if it goes down to as low as 4.5V you have a bit of a problem
there, which could account for some of the erratic behavior
you're seieng. Is there a trimpot adjustment on that power supply
board?
Nope, nothing adjustable at all.
I
used to work on those machines (we had "the shop" in a
building that had an Osborne dealer in it so I saw more of
those than any other CP/M boxes) but it's been rather a while
since I saw one. I just looked in one set of files and can't
seem to find any schematics or other stuff, though I know I
have one somewhere, so I guess I'm working from memory here.
Your assistance is much appreciated. I've still got to try Tony's suggestion
of checking out the H-sync signal, but I need to find it first...
You might locate the biggest caps on that power supply
board
(they'll have the highest voltage rating and be on the
primary side of things, probably two of
them) and give some consideration to replacing those.
I shall consider it - is there any (non-destructive: I know you can pump
240vac into it, then when the magic smoke escapes conclude it's broken :))
way to test an electrolytic cap?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1433 - Release Date: 14/05/2008
16:44
3:50 p.m.
New subject: Osborne OCC1 problem
On Thursday 15 May 2008 15:32, Ade Vickers wrote:
Yep, figured that one.
Measured with respect to Earth (green wire, goes everywhere including to
the mainboard). As far as I can tell, this acts as GND for the whole
machine?
Shielding more than anything else, I'd guess.
Well..... as my multimeter is flat & I don't have a signal generator, I
calibrated the 'scope using a 1.5v AA battery. Thus, accuracy is far from
guaranteed...
Even still, it shouldn't be fluctuating either.
Hm.
Hopefully I'll find my Osborne tech docs one of these days.
It'll be on that connector on the front, and prety obvious which one it is
because of the repetition rate, as opposed to the much lower rate for the
vertical sync, and the much erratic nature of the video. And if it's *way*
off in frequency or changes a lot or has a lot of jitter than we're probably
looking at the power supply not being right.
With some equipment, yeah. The least I'd want is to use an isolation
transformer to plug the computer into and then scope across the main filter
caps and see what you get, but I wouldn't care to mess around in there
without an isolation transformer.
If they're bulgy on top they're bad.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Roy J. Tellason wrote:
OK. I'm not sure how it gets there, as there is no connection in the plug
to take it (and there's only the single 3-wire plug leaving the PSU
board...
Hm, could be I'm mis-remembering slightly here. Or it could be used in later
stuff. I recall seeing only one or two of the tan case units, most of them
were the later ones.
I have
concluded that, with respect to GND:
Pin 1 has approx -13.5v - but is not connected to anything
That's the nominal -12V, and it's used in the RS232 port and
nowhere else that I can recall. Pin 2 has approx +12.0v
That's the nominal +12, and is used in the RS232 port and
the disk drives. Pin 3 has
approx - 0.1v (and is a bit rough, but only on
the millivolt scale)
Measured with respect to where? That's probably your ground pin. Pin 4 has approx + 4.5v (higher, actually, somewhere
between 4.5v and 5.0v
That should be +5 give or take a quarter volt and no more,
if it goes down to as low as 4.5V you have a bit of a problem
there, which could account for some of the erratic behavior
you're seieng. As I say, it IS a little higher than 4.5v - it may be
4.75, but I couldn't
be sure of that. I will find a new battery for the multimeter tonight...
Yeah, I'd see where that ends up because it being off could affect everything
like we're seeing here.
Is there a
trimpot adjustment on that power supply board?
Nope, nothing adjustable at all. I used to work
on those machines (we had "the shop" in a building that had
an Osborne dealer in it so I saw more of those than any other CP/M boxes)
but it's been rather a while since I saw one. I just looked in one set of
files and can't seem to find any schematics or other stuff, though I know
I have one somewhere, so I guess I'm working from memory here.
Your assistance is much appreciated. I've still got to try Tony's suggestion
of checking out the H-sync signal, but I need to find it first... You might
locate the biggest caps on that power supply board
(they'll have the highest voltage rating and be on the primary side of
things, probably two of them) and give some consideration to replacing
those.
I shall consider it - is there any (non-destructive: I know you can pump
240vac into it, then when the magic smoke escapes conclude it's broken :))
way to test an electrolytic cap?
7:48 p.m.
New subject: Osborne OCC1 problem
Roy J. Tellason wrote :
OK, that would make sense. In which case, I'd expect the differential
between pins 3 & 4 to be approx 5v, but will confirm tomorrow.
Should I probe these with reference to the GND (Earth/shield) or the 0v line
(pin 3, as above)?
They look brand new TBH. Not even any dust on them (probably because the PSU
is mounted component-side-down in the case). That, and the case itself is
pretty tightly sealed when the unit is assembled & closed up.
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1433 - Release Date: 14/05/2008
16:44
Hm, could be I'm mis-remembering slightly here.
Or it could
be used in later stuff. I recall seeing only one or two of
the tan case units, most of them were the later ones.
I sold my non-tan cased Ozzie, on the basis it wasn't rare enough for my
liking! Of course, that one worked perfectly...
Measured with
respect to Earth (green wire, goes everywhere
including
to the mainboard). As far as I can tell, this
acts as GND for the
whole machine?
Shielding more than anything else, I'd guess.
Even still, it shouldn't be fluctuating either.
My mistake - there was no fluctuation, except in the optics of the sensor
(me & my eyes). The voltage output was a perfectly flat line (except when
the 'scope sensitivity was turned to 20mv/cm, at which point I could just
about see some rectification effects - but getting the 'scope to trigger on
the peaks was really hard work; it's a pretty flat line.
The signal on Pin 3 (-0.1v I guessed at) was a little noiser, but seemed to
be random noise. Having said that, I didn't "zoom in" on it so much.
If, as you imply, Pin 3 is GND and Pin 4 is +5v; then the difference between
those two is much closer to 5v than between Pin 4 & Earth.
Your assistance is much appreciated. I've still got to try Tony's
suggestion of checking out the H-sync signal, but I need to
find it first...
It'll be on that connector on the front, and prety obvious
which one it is because of the repetition rate, as opposed
to the much lower rate for the vertical sync, and the much
erratic nature of the video. And if it's *way* off in
frequency or changes a lot or has a lot of jitter than we're
probably looking at the power supply not being right. I shall
consider it - is there any (non-destructive: I know you can
pump 240vac into it, then when the magic smoke escapes
conclude it's
broken :)) way to test an electrolytic cap?
With some equipment, yeah. The least I'd want is to use an
isolation transformer to plug the computer into and then
scope across the main filter caps and see what you get, but
I wouldn't care to mess around in there without an isolation
transformer.
If they're bulgy on top they're bad.
10:04 p.m.
New subject: Osborne OCC1 problem
On Thursday 15 May 2008 19:48, Ade Vickers wrote:
OK, that would make sense. In which case, I'd expect the differential
between pins 3 & 4 to be approx 5v, but will confirm tomorrow.
Ok.
Ok...
Should I probe these with reference to the GND (Earth/shield) or the 0v
line (pin 3, as above)?
I'd find a convenient ground point. Beside the ones on the power supply there
are no doubt others on the mainboard and at least one on that edge connector.
They look brand new TBH. Not even any dust on them (probably because the
PSU is mounted component-side-down in the case). That, and the case itself
is pretty tightly sealed when the unit is assembled & closed up.
A bit of a contrast to my Exec, which has a fan in it, that I replaced with
a slightly stronger (AC) one. :-) That was a retrofit done by several O-1
owners that I know of that wanted cooler and more reliable operation. All
you need to do is replace the bit under the handle with one that has the fan
opening, at least on the gray case.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Roy J. Tellason wrote :
I'd have kept it for spare parts, at least -- inside they're basically the
same...
Hm, could be I'm mis-remembering slightly
here. Or it could
be used in later stuff. I recall seeing only one or two of
the tan case units, most of them were the later ones.
I sold my non-tan cased Ozzie, on the basis it wasn't rare enough for my
liking! Of course, that one worked perfectly... Measured with respect to Earth (green wire, goes
everywhere
including to the mainboard). As far as I can tell, this acts as GND for
the whole machine?
Shielding more than anything else, I'd guess. Even still,
it shouldn't be fluctuating either.
My mistake - there was no fluctuation, except in the optics of the sensor
(me & my eyes). The voltage output was a perfectly flat line (except when
the 'scope sensitivity was turned to 20mv/cm, at which point I could just
about see some rectification effects - but getting the 'scope to trigger on
the peaks was really hard work; it's a pretty flat line.
The signal on Pin 3 (-0.1v I guessed at) was a little noiser, but seemed to
be random noise. Having said that, I didn't "zoom in" on it so much.
If, as you imply, Pin 3 is GND and Pin 4 is +5v; then the difference
between those two is much closer to 5v than between Pin 4 & Earth. Your assistance is much appreciated. I've still
got to try Tony's
suggestion of checking out the H-sync signal, but I need to
find it first...
It'll be on that connector on the front, and prety obvious
which one it is because of the repetition rate, as opposed
to the much lower rate for the vertical sync, and the much
erratic nature of the video. And if it's *way* off in
frequency or changes a lot or has a lot of jitter than we're
probably looking at the power supply not being right. I shall consider it - is there any (non-destructive: I
know you can
pump 240vac into it, then when the magic smoke escapes
conclude it's broken :)) way to test an electrolytic cap?
With some equipment, yeah. The least I'd want is to use an
isolation transformer to plug the computer into and then
scope across the main filter caps and see what you get, but
I wouldn't care to mess around in there without an isolation
transformer.
If they're bulgy on top they're bad.
6:15 p.m.
New subject: Osborne OCC1 problem
It's going to have to be the 'scope... I
failed to turn the multimeter off
properly last time I used it, and now the battery is flat. Doh!
Quite a few of my multimeters only need a battery for the resistance
ranges... They're analogue, of course.
And a few others run off the mains....
Or, of course, I could bodge my universal power supply
into powering the
Be careful doing that if one side of the universal PSU is grounded. Quite
a few simple DMM circutis do not have the -ve side of the battery
connected to the -ve input terminal.
multimeter...... (don't dare suggest buying a
battery! ;))
Unless your meter takes some obscure battery, I am suprised you don't
have them in stock. ...
-tony
7:40 p.m.
New subject: Osborne OCC1 problem
Tony Duell wrote:
Mmm, I have an analogue MM somewhere - can't remember where, though, and
IIRC the selector switch had become almost unusably jammed - requiring an
unfeasible amount of force to turn it. I've got it *somewhere*, goodness
knows where.
It's going
to have to be the 'scope... I failed to turn the
multimeter
off properly last time I used it, and now the
battery is flat. Doh!
Quite a few of my multimeters only need a battery for the
resistance ranges... They're analogue, of course.
Unless your meter takes some obscure battery, I am suprised
you don't have them in stock. ...
9v PP3. Haven't bought one of those in years.
*smacks head* I will have some for my Sinclair Cambridge Programmables... if
I can remember where I put them. In my defence, I *do* have a 4000sqft
warehouse to search, and it's not in any particular order...
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1433 - Release Date: 14/05/2008
16:44
9:59 p.m.
New subject: Osborne OCC1 problem
On Thursday 15 May 2008 19:40, Ade Vickers wrote:
In my defence, I *do* have a 4000sqft warehouse to
search, and it's not in
any particular order...
If I had that much space to keep stuff in, I'd have to spend at least some
small amount of time organizing it or I'd go crazy...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
16 May
16 May
5:08 a.m.
New subject: Osborne OCC1 problem
Roy J. Tellason wrote:
:)
A lot of the space goes to storing stuff to do with cars - I have 2 racing
cars, 5 road cars & a kit car in there at the moment, and a coach (bus). But
there's a load of old computers in there as well... And the Sinclair
Programmables are very very small...
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1445 - Release Date: 15/05/2008
19:25
In my defence,
I *do* have a 4000sqft warehouse to search, and it's
not in any particular order...
If I had that much space to keep stuff in, I'd have to spend
at least some small amount of time organizing it or I'd go crazy...
8:48 p.m.
New subject: Osborne OCC1 problem
On Friday 16 May 2008 05:08, Ade Vickers wrote:
Roy J. Tellason wrote:
:)
A lot of the space goes to storing stuff to do with cars - I have 2 racing
cars, 5 road cars & a kit car in there at the moment, and a coach (bus).
But there's a load of old computers in there as well... And the Sinclair
Programmables are very very small...
Cheers!
Ade.
Currently I'm dealing with a 10x22 ft garage for some stuff, and the fact
that I haven't spent at least some time over there today bothers me... :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
In my
defence, I *do* have a 4000sqft warehouse to search, and it's
not in any particular order...
If I had that much space to keep stuff in, I'd have to spend
at least some small amount of time organizing it or I'd go crazy...
15 May
15 May
9:57 p.m.
New subject: Osborne OCC1 problem
On Thursday 15 May 2008 18:15, Tony Duell wrote:
Indeed. My Simpson 461 for one example, will suffer some nontrivial damage
if you connnect either of the test leads to either of the battery
connections -- blows up some resistors and a reference diode, from what I
recall. Dumb way to design something, but...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Or, of course,
I could bodge my universal power supply into powering the
Be careful doing that if one side of the universal PSU is grounded. Quite
a few simple DMM circutis do not have the -ve side of the battery
connected to the -ve input terminal.
multimeter...... (don't dare suggest buying a battery! ;))
Unless your meter takes some obscure battery, I am suprised you don't
have them in stock. ...
-tony
6:08 p.m.
New subject: Osborne OCC1 problem
I'll have to do some tracing, but I think they are
separate V & H. There are
10 wires going from the mainboard to the monitor, but not sure what signals
they carry.
There is a de-facto 'standard' for 10 pin monitors (using a 0/156" pitch
edge connector or header plug). The DEC VT100 monitor PCB is one such, if
you need more details...
sync circuit. It's unlikely to be a digial
problem. And this
is a horizontal problem (picture breaks up into sloping
likes)not a vertical problem (picture rolls), right?
Hmm; I don't think it is wholly an analogue problem: I would expect the
screen to break into horizontal slopes, as you say - and I've seen that on
badly adjusted monitors in the past (I used to have an old Philips monitor
which could be provoked into this with the front panel adjusters).
What's happening is a corruption of the display, rather than an adjustment fault. For example, I just booted the machine again,
and (ever so briefly)
got an entire screenful of the letter "U". Then it went away, and the
Osborne logo came back (and that *did* show some signs of an analogue issue
- the horizontal slopes; but lots of them, not just a few). There's no way a
horizontal hold failure could cause the screen to be filled with "U"s...
Correct. Taht implies a digital prolem, and not necessarily in the video
circuitry....
Does this machine use a 6845 or similar for hre video timing chain? If
so, mis-programming that will cause apparent sync problems. So the fault
could bever well be proscessor, ROM, or bus related.
That's why I'd start by looking at the horizotnal sync pulses when you
have the lines and when you have a good display (even if the machine has
crashed). If they're the same timing, then the fault is monotor (or PSU?)
releated. If not, then the video timing circuitry is palying up _or being
mis-configured by software_
If you do have seaprate signals to the monitor,
start by
'scoping the horizontal sync signal while the monitor is
malfunctioning. Is it the right frequency and stable?
I'll look for it... the monitor circuit board is quite well labeled; but I'm
not sure if the connectors themselves have individually labelled
connections. Question: How long should I leave the tube to
"cool down" (unplugged) before
I can rummage around it without fear of major electrocution?
Depends on what you're working on, and the design of the monitor. The
PCB-mounted capacitors will normally discharge fairly fast (minute at
most), so there'll be no masty votlages on PCB tracks or CRT _pins_ after
that. The EHT, stored in the 'capacitor' of the CRT glass can stay for
days, but (a) it'll be discharrged by the beam current in any normal
monitor (so this is really only a concern if the screen is totally
blank), () the only way you'll get in contact with it is if you remove
the anonde connector and (c) good monitors have a bleeder resistor, often
inside the flyback trasnformer.
If I am going to be removing the EHT connector, I check the residual
voltage with an EHT voltmeter (which also happens to discharge it :-)).
Otherwise, I don't worry. So far I've never had a shock doing that.
-tony
7:48 p.m.
New subject: Osborne OCC1 problem
Tony Duell wrote:
Well, the video I linked to is about the best description I could think
of...
When the screen is showing static information, and the disk(s) are not
running, then the display kind of looks like it's got a h-synch problem. Or,
try this: It looks like there's a strong right-to-left motion blur. That's
still not 100% accurate, but I'm no artist & trying to describe it is beyond
my ken.
When the machine is booting from disk, the screen flashes and flickers like
a mad thing: But as I say, it seems to be *digital* noise rather than
analogue. But with some analogue effects thrown in for good measure...
Maybe I should monitor the PSU voltage on the 'scope while the machine's
booting - I hadn't thought of that one. Could be interesting - the bulk of
the computer is currently upside down on the bench to make it easy to access
the bits of the PSU I need to probe... if the 5v line is flapping about,
this could cause the digital effects. Mind you, the fact the machine boots
properly indicates that the logic side of the machine is working fine; and
I'd have thought the disk drive would be more sensitive to 12v fluctuations
than the monitor?
I've not counted the pins, but one thing - where's the brightness control
go? The machine has external (to the monitor) controls for both contrast &
bright; as well as trimpots for both on the monitor PCB itself.
Shouldn't be a problem; the screen is lit up, so I guess it's discharging.
Hmm; I
don't think it is wholly an analogue problem: I would expect
the screen to break into horizontal slopes, as you say -
and I've seen
that on badly adjusted monitors in the past (I
used to have an old
Philips monitor which could be provoked into this with the
front panel
adjusters).
What's happening is a corruption of the display, rather than an
adjustment
A more accurate fault description would be helpful... Does this machine use a 6845 or similar for hre video
timing
chain?
Dunno, will look tomorrow (err, later today).
If so, mis-programming that will cause apparent sync
problems. So the fault could bever well be proscessor, ROM,
or bus related.
Bearing in mind the machine boots, and works behind its corrupted video
output, would that necessarily eliminate any of those parts from enquiries?
That's why I'd start by looking at the
horizotnal sync pulses
when you have the lines and when you have a good display
(even if the machine has crashed). If they're the same
timing, then the fault is monotor (or PSU?) releated. If not,
then the video timing circuitry is palying up _or being
mis-configured by software_
Gotcha - will look at that tomorrow.
I'll look
for it... the monitor circuit board is quite well
labeled;
but I'm not sure if the connectors themselves
have individually
labelled connections.
Sony were sometimes kind enough to label connector pins,
supply lines, CRT pinouts, etc in the slikscreen, few other
manufacturers were.
If it is a standard pinout, then the connections are
1 Ground
2 One end of the contrast control
3 t'other end of the contrast control
4 Slider of the contrast control
5 ground
6 Hsync
7 +12V power input
8 video input
9 Vsync
10 ground Question: How
long should I leave the tube to "cool down"
(unplugged)
before I can rummage around it without fear of
major electrocution?
Depends on what you're working on, and the design of the
monitor. The PCB-mounted capacitors will normally discharge
fairly fast (minute at most), so there'll be no masty
votlages on PCB tracks or CRT _pins_ after that. The EHT,
stored in the 'capacitor' of the CRT glass can stay for days,
but (a) it'll be discharrged by the beam current in any
normal monitor (so this is really only a concern if the
screen is totally blank), () the only way you'll get in
contact with it is if you remove the anonde connector and (c)
good monitors have a bleeder resistor, often inside the
flyback trasnformer.
No plans to remove any connectors inside the monitor....
If I am going to be removing the EHT connector, I check the
residual voltage with an EHT voltmeter (which also happens to
discharge it :-)).
Otherwise, I don't worry. So far I've never had a shock doing that.
OK, that's good to know. Many thanks again Tony - I'll try to report back
the status of the h-sync tomorrow.
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1433 - Release Date: 14/05/2008
16:44
10:10 p.m.
New subject: Osborne OCC1 problem
On Thursday 15 May 2008 19:48, Ade Vickers wrote:
(Snip)
I believe so, though it's been a long time and I can't be 100% certain of it.
Not necesarily.
I've not counted the pins, but one thing - where's the brightness control
go? The machine has external (to the monitor) controls for both contrast &
bright; as well as trimpots for both on the monitor PCB itself.
Darn, I *really* need to find my schematics on this stuff... :-)
(Snip)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Maybe I should monitor the PSU voltage on the
'scope while the machine's
booting - I hadn't thought of that one. Could be interesting - the bulk of
the computer is currently upside down on the bench to make it easy to
access the bits of the PSU I need to probe... if the 5v line is flapping
about, this could cause the digital effects. Mind you, the fact the machine
boots properly indicates that the logic side of the machine is working
fine; and I'd have thought the disk drive would be more sensitive to 12v
fluctuations than the monitor?
The drive only uses the 12V for the spindle motor, I think, but do check
them both.
And clean the edge connectors for the drive ribbon cable too, that's been a
trouble spot in my experience, what with them running power through the
ribbon cable.
Does this
machine use a 6845 or similar for hre video timing
chain?
Dunno, will look tomorrow (err, later today). If so,
mis-programming that will cause apparent sync
problems. So the fault could bever well be proscessor, ROM,
or bus related.
Bearing in mind the machine boots, and works behind its corrupted video
output, would that necessarily eliminate any of those parts from enquiries? That's why
I'd start by looking at the horizotnal sync pulses
when you have the lines and when you have a good display
(even if the machine has crashed). If they're the same
timing, then the fault is monotor (or PSU?) releated. If not,
then the video timing circuitry is palying up _or being
mis-configured by software_
Gotcha - will look at that tomorrow.
I'll
look for it... the monitor circuit board is quite well labeled; but
I'm not sure if the connectors themselves have individually labelled
connections.
Sony were sometimes kind enough to label connector pins,
supply lines, CRT pinouts, etc in the slikscreen, few other
manufacturers were.
If it is a standard pinout, then the connections are
1 Ground
2 One end of the contrast control
3 t'other end of the contrast control
4 Slider of the contrast control
5 ground
6 Hsync
7 +12V power input
8 video input
9 Vsync
10 ground
16 May
16 May
3:24 p.m.
New subject: Osborne OCC1 problem
What's happening is a corruption of the display,
rather than an
adjustment
A more accurate fault description would be helpful...
When the screen is showing static information, and the disk(s) are not
running, then the display kind of looks like it's got a h-synch problem. Or,
try this: It looks like there's a strong right-to-left motion blur. That's
still not 100% accurate, but I'm no artist & trying to describe it is beyond
my ken.
When the machine is booting from disk, the screen flashes and flickers like
a mad thing: But as I say, it seems to be *digital* noise rather than
analogue. But with some analogue effects thrown in for good measure...
That sounds _very_ like PSU trouble to me. The disk drive motors take
significant current, and that's pulling one of the supply rails down and
casuing all sorts of prolems.
The average voltage of the supply line, as measured by a mulitmeter, may
not change much, but a 'scope would show masty dips in the voltage
Maybe I should monitor the PSU voltage on the 'scope while the machine's
booting - I hadn't thought of that one. Could be interesting - the bulk of
the computer is currently upside down on the bench to make it easy to access
the bits of the PSU I need to probe... if the 5v line is flapping about,
this could cause the digital effects. Mind you, the fact the machine boots
properly indicates that the logic side of the machine is working fine; and
I'd have thought the disk drive would be more sensitive to 12v fluctuations
than the monitor?
If it is a
standard pinout, then the connections are
1 Ground
2 One end of the contrast control
3 t'other end of the contrast control
4 Slider of the contrast control
5 ground
6 Hsync
7 +12V power input
8 video input
9 Vsync
10 ground
I've not counted the pins, but one thing - where's the brightness control
go? The machine has external (to the monitor) controls for both contrast &
bright; as well as trimpots for both on the monitor PCB itself.
17 May
17 May
11:34 a.m.
New subject: Osborne OCC1 problem
Tony Duell wrote:
Hmm, yes, I can see how that might cause problems...
I could run the picture through an ascii-art generator if that would help?
;)
I've 'scoped the 12v & 5v lines both in "steady state" and
"booting" now;
both are remarkably stable (a bit of noise on the 5v line when booting, but
in the millivolt range. The 12v line rises slightly when you unplug the
monitor, which is not a big surprise since the monitor will, obviously, be
drawing power.
Basically, these readings over-ride any which have gone before....:
12v line = 12.75v, no discernable change or noise when booting or stable.
Slight rise (unmeasured) when power to monitor is withdrawn.
5v line = 5.4v, dropping to 5.3 between Vss and Vcc of one of the logic
chips. Generally pretty stable, some slight noise whilst booting.
There is NO difference between the voltages when the machine is running
(video blurry) or crashed (video stable).
Hsync remains rock solid whether crashed or running. I couldn't accurately
gauge the pulse width as I don't have a signal generator to calibrate the
'scope with.
Well, the
video I linked to is about the best description I could
think of...
Which is not a lot of help to those of us with a text-only
display, and to whom 'video recording' means a Philips N1500
or V2000 tape... When the
machine is booting from disk, the screen flashes
and flickers
like a mad thing: But as I say, it seems to be
*digital*
noise rather
than analogue. But with some analogue effects
thrown in for
good measure...
That sounds _very_ like PSU trouble to me. The disk drive
motors take significant current, and that's pulling one of
the supply rails down and casuing all sorts of prolems. The average voltage of the supply line, as measured by
a
mulitmeter, may not change much, but a 'scope would show
masty dips in the voltage
None visible.
Well, it might be a non-standard pinout, then :-(. Or
is
there a separate
3-wire cable for the brightness pot? I've seen that several times.
Brightness goes to the monitor. The contrast, I've discovered, is just the
Video Out signal passing through a variable resistor. Simple, really...
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1448 - Release Date: 16/05/2008
19:42
16 May
16 May
8:01 a.m.
New subject: Osborne OCC1 problem
Tony Duell wrote:
There is a de-facto 'standard' for 10 pin
monitors (using a
0/156" pitch edge connector or header plug). The DEC VT100
monitor PCB is one such, if you need more details...
Looks like the standard has been used... enough pins seemed to match up with
your description, that I went with it.
So, here are the two traces, hsync & vsync:
http://www.solutionengineer.com/ozzie/hsync.jpg
http://www.solutionengineer.com/ozzie/vsync.jpg
Apologies about the quality of the hsync one, the camera seems to have
refocussed itself on its own reflection...
That's why I'd start by looking at the
horizotnal sync pulses
when you have the lines and when you have a good display
(even if the machine has crashed). If they're the same
timing, then the fault is monotor (or PSU?) releated. If not,
then the video timing circuitry is palying up _or being
mis-configured by software_
H-sync pulses (and the vsync, for what it's worth) are identical when the
machine is crashed or running. However, I don't understand why that would
put the fault in the monitor? And it still doesn't explain the digital
artifacts...
There does seem to be a significant amount of noise coming off the board; I
could get a reading on the 'scope when the probe was a good 2-3cm away from
the board - not sure WHAT signal, just a square-ish peak in the middle of
the screen...
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1445 - Release Date: 15/05/2008
19:25
12:22 p.m.
New subject: Osborne OCC1 problem
Right, I've now multimetered the voltages, and:
The 12v line is running at 12.74v
The 5v line is running at 5.40v
I didn't check the -13v line
I took readings from a couple places: Straight off the PSU plug, and in the
case of the 12v, at the monitor plug.
I wasn't sure about the 5v; I took a reading across each of the 8132 chips,
getting 4.14v and 4.16v; but I guess those may not be meaningful as the chip
itself will be taking some of that power.
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1445 - Release Date: 15/05/2008
19:25
3:35 p.m.
New subject: Osborne OCC1 problem
Right, I've now multimetered the voltages, and:
The 12v line is running at 12.74v
The 5v line is running at 5.40v
I didn't check the -13v line
I took readings from a couple places: Straight off the PSU plug, and in the
case of the 12v, at the monitor plug.
I wasn't sure about the 5v; I took a reading across each of the 8132 chips,
getting 4.14v and 4.16v; but I guess those may not be meaningful as the chip
itself will be taking some of that power.
Hang on, are you saying you're getting 5.4V at the output of the PSU and
4.16V across the power and ground pins of a chip on the logic board?
The fact that the ship is drawing current _should be_ irrelevant. The
voltage is being droppead across the impedance of the supply connections
(wiring, connectors, PCB tracks) betweem the PSU and chip, and that
impedance should be low enough not to drop 1V or more.
And that could well be your problem. A high impedance (relatively) supply
or ground connection can cause 'intersting' voltage drops when anything
starts drawing current. And that'll lead to things not working.
-tony
17 May
17 May
9:47 a.m.
New subject: Osborne OCC1 problem
Tony Duell wrote:
Hang on, are you saying you're getting 5.4V at the output of
the PSU and 4.16V across the power and ground pins of a chip
on the logic board?
I am, but I was wrong... I'd got the wrong pin; in fact, the voltage drop
(on the multimeter) is 0.1v (5.4v to 5.3v) when I use the "correct" GND pin.
And the chip is an F6821P, not an 8132 (I'd read the wrong number, and got
that wrong too... blame my flaky memory).
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1448 - Release Date: 16/05/2008
19:42
16 May
16 May
8:56 p.m.
New subject: Osborne OCC1 problem
On Friday 16 May 2008 12:22, Ade Vickers wrote:
Right, I've now multimetered the voltages, and:
The 12v line is running at 12.74v
The 5v line is running at 5.40v
A little high in both cases.
I didn't check the -13v line
I took readings from a couple places: Straight off the PSU plug, and in the
case of the 12v, at the monitor plug.
I wasn't sure about the 5v; I took a reading across each of the 8132 chips,
getting 4.14v and 4.16v; but I guess those may not be meaningful as the
chip itself will be taking some of that power.
8132 chips?
That's *definitely* too low, if it's supposed to be +5V. Enough to cause the
logic to act quite strangely...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
10:53 p.m.
New subject: Osborne OCC1 problem
From: rtellason at verizon.net
On Friday 16 May 2008 12:22, Ade Vickers wrote:
Hi
These are bus buffers. It does sound like there is a bbad ground path.
He should try using a good jumper to cross connect the ground.
Dwight
_________________________________________________________________
Change the world with e-mail. Join the i?m Initiative from Microsoft.
http://im.live.com/Messenger/IM/Join/Default.aspx?source=EML_WL_ChangeWorld
Right, I've now multimetered the voltages,
and:
The 12v line is running at 12.74v
The 5v line is running at 5.40v
A little high in both cases.
I didn't check the -13v line
I took readings from a couple places: Straight off the PSU plug, and in the
case of the 12v, at the monitor plug.
I wasn't sure about the 5v; I took a reading across each of the 8132 chips,
getting 4.14v and 4.16v; but I guess those may not be meaningful as the
chip itself will be taking some of that power.
8132 chips?
17 May
17 May
2:06 p.m.
New subject: Osborne OCC1 problem
I wasn't
sure about the 5v; I took a reading across each of the 8132 ch=
ips,
getting 4.14v and 4.16v; but I guess those may
not be meaningful as the
chip itself will be taking some of that power.
8132 chips?
That's *definitely* too low, if it's supposed to be +5V. Enough to caus=
e the=20
logic to act quite strangely...
16 May
16 May
3:31 p.m.
New subject: Osborne OCC1 problem
That's why
I'd start by looking at the horizotnal sync pulses
when you have the lines and when you have a good display
(even if the machine has crashed). If they're the same
timing, then the fault is monotor (or PSU?) releated. If not,
then the video timing circuitry is palying up _or being
mis-configured by software_
H-sync pulses (and the vsync, for what it's worth) are identical when the
machine is crashed or running. However, I don't understand why that would
put the fault in the monitor? And it still doesn't explain the digital
artifacts...
9 p.m.
New subject: Osborne OCC1 problem
On Friday 16 May 2008 15:31, Tony Duell wrote:
Well, if the Hsync pulses are indential whether the display is stable or
not, then the Hsync generation circuitry is not the prolem. And if the
monitor is not locking to them, the fault is either the monitor or the
PSU, presumably.
Without any indication of amplitude or repetition rate it's hard to say
whether they're good Hsync pulses or not. The image of that Vsync pulse sure
looks a little odd to me...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
That's why I'd start by looking at the
horizotnal sync pulses
when you have the lines and when you have a good display
(even if the machine has crashed). If they're the same
timing, then the fault is monotor (or PSU?) releated. If not,
then the video timing circuitry is palying up _or being
mis-configured by software_
H-sync pulses (and the vsync, for what it's worth) are identical when the
machine is crashed or running. However, I don't understand why that would
put the fault in the monitor? And it still doesn't explain the digital
artifacts...
9:32 p.m.
New subject: Osborne OCC1 problem
On Friday 16 May 2008 21:00, Roy J. Tellason wrote:
On Friday 16 May 2008 15:31, Tony Duell wrote:
Well, if the Hsync pulses are indential whether the display is stable or
not, then the Hsync generation circuitry is not the prolem. And if the
monitor is not locking to them, the fault is either the monitor or the
PSU, presumably.
Without any indication of amplitude or repetition rate it's hard to say
whether they're good Hsync pulses or not. The image of that Vsync pulse
sure looks a little odd to me...
The tech manual pointed to in another post gives a nice set of diagrams for
what those sync pulses _should_ look like, around 43 or so pages into it...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
That's why I'd start by looking at the
horizotnal sync pulses
when you have the lines and when you have a good display
(even if the machine has crashed). If they're the same
timing, then the fault is monotor (or PSU?) releated. If not,
then the video timing circuitry is palying up _or being
mis-configured by software_
H-sync pulses (and the vsync, for what it's worth) are identical when
the machine is crashed or running. However, I don't understand why that
would put the fault in the monitor? And it still doesn't explain the
digital artifacts...
17 May
17 May
9:47 a.m.
New subject: Osborne OCC1 problem
Tony Duell:
Well, if the Hsync pulses are indential whether the
display
is stable or not, then the Hsync generation circuitry is not
the prolem. And if the monitor is not locking to them, the
fault is either the monitor or the PSU, presumably.
As the monitor will lock to them when the computer has crashed, I wonder if
it's noise from somewhere interfering with the video signal generation? Or,
perhaps, the monitor itself is being subjected to noise which is trashing
the display.
Whatever the cause, it's definitely only when the machine is running that
the problem manifests itself.
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.16/1448 - Release Date: 16/05/2008
19:42
18 May
18 May
6:50 p.m.
Ade Vickers wrote:
MOV format (4mb):
http://www.solutionengineer.com/ozzie/occ1_prb.mov
Something in the video generator circuit on the digital side by the looks of
things. Probably pre-character-generator -- those characters look fine and
they're in the right place, but they're the wrong characters. So that's
anything pre-character-generator basically -- buffers, latches, RAM, not
necessarily in that order.
Point me to a PDF of the schematic and I'll see if my overworked brain can
come up with any other ideas :)
Any ideas where to start looking? I have an
oscilloscope (albeit I've
forgotten how to use it, and am not 100% sure where the probes are), and a
multimeter... beyond that, not a lot.
Have a read through the Tektronix "ABCs of Oscilloscopes" guide - that's on
<http://www.tek.com/> somewhere (their search engine usually works fairly
well, or try Google). That should be enough of a reminder of the terminology,
and how to make the scope work.
Now the things I'd try in order:
Set the scope to 0.5V/div, AC coupled and connect it between +5V and
ground. See if there's any significant noise on there. If there's around 0.1V
or less of noise / pulsing on the power line, you should be fine. Any more
than that and you want to check the power filtering. Check using various
ground and +5V points -- this might expose a bad track or via.
Does the keyboard work, or is the machine totally crashed after booting
(assuming you leave the terminator where it is)? Does a CAT (or DIR, or
whatever the relevant CP/M command is) show something similar to a directory list?
Check the address lines for the display RAM. If it's DRAM you're pretty
much screwed, but with SRAM you can see if the count is incrementing normally
or if there's an output line stuck low.
If the RAMs are socketed (and the same type), try swapping them around. If
you know the main RAM is good, swap each VRAM chip with a main-RAM chip until
either the main RAM test fails or the video stops glitching. This, of course,
only works if the main and video RAMs are the same type.
Basically, everything works except for the shaky
video. Sometimes you see a
whole page full of 1s, or 0s; essentially, it's all a bit random. Bad
connection somewhere, perhaps, or maybe a failing chip?
A screen full of one character may well be a power-on test or something
similar... If it's happening after power up then something is very badly wrong.
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
7:07 p.m.
Philip Pemberton wrote:
Something in the video generator circuit on the
digital side by the
looks of things. Probably pre-character-generator -- those characters
look fine and they're in the right place, but they're the wrong
characters. So that's anything pre-character-generator basically --
buffers, latches, RAM, not necessarily in that order.
I've just seen the MPEG -- looks like what you're seeing is the counter (or a
latch, flipflop or buffer) sticking. It's holding an address for a few
characters instead of a single character period.
If you run the video frame-by-frame, you see it displaying:
Loading CP/M and HELP...
which turns into
LLLLLnnnnn////nd HHHHHH.......
or something to that effect - the video isn't fantastically clear.
So you want to look at:
- counters
- buffers / flipflops / latches
- latch / enable logic for the above
That's on top of checking the PSU as I mentioned in my last email.
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
8:48 p.m.
Philip Pemberton wrote:
I've just seen the MPEG -- looks like what
you're seeing is
the counter (or a latch, flipflop or buffer) sticking. It's
holding an address for a few characters instead of a single
character period.
If you run the video frame-by-frame, you see it displaying:
Loading CP/M and HELP...
which turns into
LLLLLnnnnn////nd HHHHHH.......
or something to that effect - the video isn't fantastically clear.
Excellent spot, thanks. Apologies about the poor video - it was taken
handheld using an elderly digital camera (Olympus UZ-2100 - in about 2 years
time, it'll qualify as a classic for this list!).
So you want to look at:
- counters
- buffers / flipflops / latches
- latch / enable logic for the above
That's on top of checking the PSU as I mentioned in my last email.
I've almost ruled out the PSU, the +5v and +12v lines are very stable, even
under load (booting). I've also got the schematics (thanks to a link found
by Roy Tellason), so I can probably find the duff chip -- well, I can try at
least. I've got the 'scope working too, but as it's not a storage scope,
seeing logic waveforms is not easy (impossible, in fact).
So... how do I find a sticky counter? Is it likely to be an on-chip fault,
or a failed track? My guess is on-chip, given that the video is clear &
stable when the machine is crashed.
Also, for clarity: Underneath the video fault, the machine is performing
perfectly. It only crashes when I pull the Ext Video buffer & plug it back
in - which physically disconnects some of the video signals from the onboard
monitor, and clearly does something electrical which causes the machine to
freeze up.
One other thing - all of the chips (bar 4) are soldered to the board. This
isn't a big problem for me, I'm reasonably adept at soldering, even when
I've got lots of legs to free up; but it will be time consuming :\
Cheers,
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.20/1453 - Release Date: 18/05/2008
09:31
20 May
20 May
12:38 p.m.
New subject: Osbourne OCC1 problem - progress....
Hi again folks,
Well, following my struggles to discover what's wrong with Ozzie, I booted
today & discovered that, whilst the machine is drawing stuff on the screen,
it's nearly readable. After much trial & error, I further discovered (on a
2nd disk) a program called memtest.
Running this has revealed a bad block of memory, between 4081 and 64C1
(always a variation on xx81 and xxC1). Interestingly, the screen is
remarkably stable while this test is running.
Now... the RAM is physically arranged as a 4x8 array (according to the tech
manual); so how can I tell which chip is supposed to look after addresses
4081 through to 64C1?
I am now assuming that this bad chip is, somehow, interfering with the video
latch/counter, hence the crazy video.
Any more ideas? All gratefully received.
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.21/1455 - Release Date: 19/05/2008
17:04
1:34 p.m.
New subject: Osbourne OCC1 problem - progress 2....
OK, now the wobbly video fault's gone away - hurrah! Of course, this could
be because the machine's been on for longer than it has been in years;
perhaps it was a thermal issue. When powering off/on, I notice a little
flicker of crazy-video now, then it settles again. Maybe I'll leave it
switched off for 5 mins & see what happens.
MEMTEST still reports the same memory errors, however, thus:
ADDRESS: 4081 BAD BITS: 08
ADDRESS: 40C1 BAD BITS: 08
ADDRESS: 4181 BAD BITS: 08
ADDRESS: 41C1 BAD BITS: 08
etc., through to:
ADDRESS: 6481 BAD BITS: 08
ADDRESS: 64C1 BAD BITS: 08
Memtest itself runs a number of different tests; it's currently crashing or
resetting the machine at random intervals. Longest successful test lasted
about 1/2hr (successful insofar as it didn't crash). Now running for 2-3
mins before crashing... Note: This is memtest only, I've not tried any other
programs yet...
Hey ho, more testing to go...
If the video prb is thermal, I'm still guessing it's related to one of the
mainboard chips, rather than the monitor itself (given that it will display
random characters, rather than what I'd call analogue effects). Anyone got
any clues as to which one? I'm also wondering if it's a RAM select chip,
rather than the RAM itself?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.21/1455 - Release Date: 19/05/2008
17:04
2:40 p.m.
New subject: Osbourne OCC1 problem - progress 2....
Ade,
It could be 1 data output witch has a shortcut to VCC or ground, but also a
databuffer with a bad driver.
Best thing to do is getting your scope and measure all the data-lines before
and after the databuffer.
This should give you a clou of where to find the error.
Rik
-----Oorspronkelijk bericht-----
Van: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
Namens Ade Vickers
Verzonden: dinsdag 20 mei 2008 19:34
Aan: 'General Discussion: On-Topic and Off-Topic Posts'
Onderwerp: RE: Osbourne OCC1 problem - progress 2....
OK, now the wobbly video fault's gone away - hurrah! Of course, this could
be because the machine's been on for longer than it has been in years;
perhaps it was a thermal issue. When powering off/on, I notice a little
flicker of crazy-video now, then it settles again. Maybe I'll leave it
switched off for 5 mins & see what happens.
MEMTEST still reports the same memory errors, however, thus:
ADDRESS: 4081 BAD BITS: 08
ADDRESS: 40C1 BAD BITS: 08
ADDRESS: 4181 BAD BITS: 08
ADDRESS: 41C1 BAD BITS: 08
etc., through to:
ADDRESS: 6481 BAD BITS: 08
ADDRESS: 64C1 BAD BITS: 08
Memtest itself runs a number of different tests; it's currently crashing or
resetting the machine at random intervals. Longest successful test lasted
about 1/2hr (successful insofar as it didn't crash). Now running for 2-3
mins before crashing... Note: This is memtest only, I've not tried any other
programs yet...
Hey ho, more testing to go...
If the video prb is thermal, I'm still guessing it's related to one of the
mainboard chips, rather than the monitor itself (given that it will display
random characters, rather than what I'd call analogue effects). Anyone got
any clues as to which one? I'm also wondering if it's a RAM select chip,
rather than the RAM itself?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.21/1455 - Release Date: 19/05/2008
17:04
21 May
21 May
12:31 a.m.
New subject: Osbourne OCC1 problem - progress 2....
Hi
Swap some of the RAMs. If the bit moves, it is the RAM if it stays
the same, it is the decode.
It is most likely bad RAM.
Dwight
From: javickers at solutionengineers.com
OK, now the wobbly video fault's gone away - hurrah! Of course, this could
be because the machine's been on for longer than it has been in years;
perhaps it was a thermal issue. When powering off/on, I notice a little
flicker of crazy-video now, then it settles again. Maybe I'll leave it
switched off for 5 mins & see what happens.
MEMTEST still reports the same memory errors, however, thus:
ADDRESS: 4081 BAD BITS: 08
ADDRESS: 40C1 BAD BITS: 08
ADDRESS: 4181 BAD BITS: 08
ADDRESS: 41C1 BAD BITS: 08
etc., through to:
ADDRESS: 6481 BAD BITS: 08
ADDRESS: 64C1 BAD BITS: 08
Memtest itself runs a number of different tests; it's currently crashing or
resetting the machine at random intervals. Longest successful test lasted
about 1/2hr (successful insofar as it didn't crash). Now running for 2-3
mins before crashing... Note: This is memtest only, I've not tried any other
programs yet...
Hey ho, more testing to go...
If the video prb is thermal, I'm still guessing it's related to one of the
mainboard chips, rather than the monitor itself (given that it will display
random characters, rather than what I'd call analogue effects). Anyone got
any clues as to which one? I'm also wondering if it's a RAM select chip,
rather than the RAM itself?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.21/1455 - Release Date: 19/05/2008
17:04
_________________________________________________________________
E-mail for the greater good. Join the i?m Initiative from Microsoft.
http://im.live.com/Messenger/IM/Join/Default.aspx?source=EML_WL_ GreaterGood
7:10 p.m.
New subject: Osbourne OCC1 problem - progress 2....
On Wednesday 21 May 2008 00:31, dwight elvey wrote:
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Hi
Swap some of the RAMs. If the bit moves, it is the RAM if it stays
the same, it is the decode.
It is most likely bad RAM.
Dwight
Trouble is those chips aren't socketed, if I'm remembering right...
From:
javickers at solutionengineers.com
OK, now the wobbly video fault's gone away - hurrah! Of course, this
could be because the machine's been on for longer than it has been in
years; perhaps it was a thermal issue. When powering off/on, I notice a
little flicker of crazy-video now, then it settles again. Maybe I'll
leave it switched off for 5 mins & see what happens.
MEMTEST still reports the same memory errors, however, thus:
ADDRESS: 4081 BAD BITS: 08
ADDRESS: 40C1 BAD BITS: 08
ADDRESS: 4181 BAD BITS: 08
ADDRESS: 41C1 BAD BITS: 08
etc., through to:
ADDRESS: 6481 BAD BITS: 08
ADDRESS: 64C1 BAD BITS: 08
Memtest itself runs a number of different tests; it's currently crashing
or resetting the machine at random intervals. Longest successful test
lasted about 1/2hr (successful insofar as it didn't crash). Now running
for 2-3 mins before crashing... Note: This is memtest only, I've not
tried any other programs yet...
Hey ho, more testing to go...
If the video prb is thermal, I'm still guessing it's related to one of
the mainboard chips, rather than the monitor itself (given that it will
display random characters, rather than what I'd call analogue effects).
Anyone got any clues as to which one? I'm also wondering if it's a RAM
select chip, rather than the RAM itself?
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.21/1455 - Release Date:
19/05/2008 17:04
_________________________________________________________________
E-mail for the greater good. Join the i?m Initiative from Microsoft.
http://im.live.com/Messenger/IM/Join/Default.aspx?source=EML_WL_
GreaterGood
22 May
22 May
4:01 a.m.
New subject: Osbourne OCC1 problem - progress 2....
Roy J. Tellason wrote:
On Wednesday 21 May 2008 00:31, dwight elvey wrote:
You are remembering right :(
I've ordered a bunch of sockets, when they (and a few other bits I need)
arrive, I'll get them desoldered & socketed.
This should be fun :\
Meanwhile:
The zany-video problem returned the next day, fuelling my belief that it
might be a thermal issue. However, a second prolonged memtest failed to
"fix" it the way it did before. In fact, memtest carried on working (still
reporting the same problem), wheras previously it crashed the machine at
various points during proceedings.
I've put it away for the time being - I need the bench space to work on some
other machines... but Ozzie will be back... I'd like to thank everyone who's
had some input into this thread - it's been very useful.
Cheers!
Ade.
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.24.0/1459 - Release Date: 21/05/2008
17:34
Hi
Swap some of the RAMs. If the bit moves, it is the RAM if it stays
the same, it is the decode.
It is most likely bad RAM.
Dwight
Trouble is those chips aren't socketed, if I'm remembering right...
5900
days inactive
5908
days old
44 comments
7 participants
participants (7)
-
ard＠p850ug1.demon.co.uk -
classiccmp＠philpem.me.uk -
dkelvey＠hotmail.com -
dr.emiel＠xs4all.nl -
javickers＠solutionengineers.com -
rtellason＠verizon.net -
tosteve＠yahoo.com