13 Feb
2006
13 Feb
'06
11:34 a.m.
I'm trying to restore an Osborne Executive, but there seems to be
something wrong in the CRT circuitry. The machine powers up and beeps,
but I see nothing on the CRT. Fiddling with the CRT pots does nothing.
I hear none of the expected noises from the CRT circuitry, nor do I see or
smell anything burnt. Can someone here point me in the right direction?
--
David Griffith
dgriffi at cs.csubak.edu
13 Feb
13 Feb
7:58 a.m.
I'm trying to restore an Osborne Executive, but there seems to be
something wrong in the CRT circuitry. The machine powers up and beeps,
but I see nothing on the CRT. Fiddling with the CRT pots does nothing.
I hear none of the expected noises from the CRT circuitry, nor do I see or
smell anything burnt. Can someone here point me in the right direction?
Do you have schematics? I don't, I've never seen one of these, so the
below is the sort of tests I'd do on any small, conventional, mono monitor.
My first thing would be to look at the CRT heater. If it's not glowing,
then either it is open circuit (:-() or its power supply has failed.
Yiu can test the former by carfully unplugging the CRT base connector and
checking the resistance between the heater pins (3 and 4 for a 7 pin CRT,
1 and 8 for an 8 pin one, at least 99% of the time).
If the heater is OK, the supply is missing. It will either come from one
of the main PSU outputs (in which case, check for things like a fuse on
the monitor mainboard), or from the horizontal output stage.
The next thing I would do is to check the CRT voltages, including the EHT
(I have an EHT meter :-)). This may point to the fact that the horizontal
output stage isn't doing a lot -- maybe the transistor is open-circuit,
maybe it's not geting any drive, and so on.
-tony
11:57 a.m.
At 02:34 PM 2/13/2006, you wrote:
I'm trying to restore an Osborne Executive, but
there seems to be
something wrong in the CRT circuitry. The machine powers up and beeps,
but I see nothing on the CRT. Fiddling with the CRT pots does nothing.
I hear none of the expected noises from the CRT circuitry, nor do I see or
smell anything burnt. Can someone here point me in the right direction?
--
David Griffith
dgriffi at cs.csubak.edu
Just a couple of suggestions, take a look at the back of
the crt and see if the heater is lit. If not tube may be burned out
or heater voltage may not be arriving at the socket. Also try looking
at the face of the tube in a dark room with the brightness control
turned up and switching off. If there is high voltage and the tube is
just dim, you may see the raster collapse to a small dot on the screen.
Regards
Charlie Fox
Charles E. Fox Video Production
793 Argyle Rd.
Windsor Ontario Canada N8Y 3J8
519-254-4991 cfox1 at cogeco.ca
Check out The Camcorder Kindergarten
at www.chasfoxvideo.com
12:35 p.m.
David Griffith wrote:
I'm trying to restore an Osborne Executive, but there seems to be
something wrong in the CRT circuitry. The machine powers up and beeps,
but I see nothing on the CRT. Fiddling with the CRT pots does nothing.
I hear none of the expected noises from the CRT circuitry, nor do I see or
smell anything burnt. Can someone here point me in the right direction?
--
David Griffith
dgriffi at cs.csubak.edu
Check the composite video out at the RCA jack on the front
panel. The same signals drive two buffer ICs, the composite
comes through U22 and the internal CRT drive comes through u7.
There needs to be a jumper plug on the external CRT edge
connector, beside the RCA jack, in case yours is missing. That
jumpers the CRT drive signals back into the internal monitor.
John
12:42 p.m.
John C. Ellingboe wrote:
Check the composite video out at the RCA jack on the
front panel.
The same signals drive two buffer ICs, the composite comes through
U22 and the internal CRT drive comes through u7. There needs to be a
jumper plug on the external CRT edge connector, beside the RCA jack,
in case yours is missing. That jumpers the CRT drive signals back
into the internal monitor.
I'm sure I've read that that jumper plug on the Osborne
(and hence possibly on the Osborne Executive) should only
be inserted or removed with the machine powered off.
Antonio
--
Antonio carlini
arcarlini at iee.org
1:19 p.m.
John C. Ellingboe wrote:
I don't know about the executive, however on the O-1, all the jumper
does is connect the fingers on the top side of the board to the corresponding
fingers to the bottom side of the board. The jumper plug is the same size as
the cable connector for the small edge connector for a ST-506 type hard drive
- I made a jumper plug for one of my O-1's by just bridging such a connector.
A little bit if "filler glue" and a label made by photocopying the one from an
official plug, and it is almost indistinguishable from the original plug.
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Vintage computing equipment collector.
Check the composite video out at the RCA jack on
the front panel.
The same signals drive two buffer ICs, the composite comes through
U22 and the internal CRT drive comes through u7. There needs to be a
jumper plug on the external CRT edge connector, beside the RCA jack,
in case yours is missing. That jumpers the CRT drive signals back
into the internal monitor.
I'm sure I've read that that jumper plug on the Osborne
(and hence possibly on the Osborne Executive) should only
be inserted or removed with the machine powered off.
1:32 p.m.
dave04a at dunfield.com wrote:
They are the same.. I didn't know how familiar you were with
the OZ machines and some people don't know that the jumper has
to be there for the internal monitor to work.
John C. Ellingboe wrote:
I don't know about the executive, however on the O-1, all the jumper
does is connect the fingers on the top side of the board to the corresponding
fingers to the bottom side of the board. The jumper plug is the same size as
the cable connector for the small edge connector for a ST-506 type hard drive
- I made a jumper plug for one of my O-1's by just bridging such a connector.
A little bit if "filler glue" and a label made by photocopying the one from an
official plug, and it is almost indistinguishable from the original plug.
Dave Check the composite video out at the RCA jack on
the front panel.
The same signals drive two buffer ICs, the composite comes through
U22 and the internal CRT drive comes through u7. There needs to be a
jumper plug on the external CRT edge connector, beside the RCA jack,
in case yours is missing. That jumpers the CRT drive signals back
into the internal monitor.
I'm sure I've read that that jumper plug on the Osborne
(and hence possibly on the Osborne Executive) should only
be inserted or removed with the machine powered off.
1:39 p.m.
On Mon, 13 Feb 2006, a.carlini at ntlworld.com wrote:
John C. Ellingboe wrote:
That jumper pack is in place and I've only removed it once (with power
off).
--
David Griffith
dgriffi at cs.csubak.edu
Check the composite video out at the RCA jack on
the front panel.
The same signals drive two buffer ICs, the composite comes through
U22 and the internal CRT drive comes through u7. There needs to be a
jumper plug on the external CRT edge connector, beside the RCA jack,
in case yours is missing. That jumpers the CRT drive signals back
into the internal monitor.
I'm sure I've read that that jumper plug on the Osborne
(and hence possibly on the Osborne Executive) should only
be inserted or removed with the machine powered off. 
1:50 p.m.
On Mon, 13 Feb 2006, a.carlini at ntlworld.com wrote:
I'm sure I've read that that jumper plug on
the Osborne
(and hence possibly on the Osborne Executive) should only
be inserted or removed with the machine powered off.
So it says, right on the plug.
Mike Loewen mloewen at cpumagic.scol.pa.us
Old Technology http://ripsaw.cac.psu.edu/~mloewen/Oldtech/
14 Feb
14 Feb
11:35 a.m.
On Monday 13 February 2006 02:34 pm, David Griffith wrote:
I'm trying to restore an Osborne Executive, but
there seems to be
something wrong in the CRT circuitry. The machine powers up and beeps,
but I see nothing on the CRT. Fiddling with the CRT pots does nothing.
I hear none of the expected noises from the CRT circuitry, nor do I see or
smell anything burnt. Can someone here point me in the right direction?
First question is, do you have that jumper plug in place? The one that bears
a sticker about not removing it while power is on, or something to that
effect. This is visible on the front panel, and if it's not there you'll
get exactly nothing from the monitor at all. The plug I refer to is visible
at:
http://ripsaw.cac.psu.edu/~mloewen/Oldtech/Osborne/Executive4L.jpg
just to the right of the two monitor knobs and to the left of the reset
button.
If it's missing (I've encountered this on some O-1s), you can possibly jump
from top to bottom of the board in a few places and get
things working.
If this isn't the problem, then what you're most likely seeing is bad
capacitors in the monitor itself. Mine worked the last time I had it on,
but there was just a little bit of jitter to the display. I wouldn't be
surprised if it didn't work the next time I tried it, but then I have a
spare monitor tucked away that I picked up some years ago.
There's also that composite video output over on the right -- try plugging
that into something, either a TV with composite input or if you don't have
one handy the video input of a VCR to use its modulator to feed into the TV.
I happen to have a Zenith 12" amber monitor that I used for this purpose as
well.
If you don't get any display at all, then there may be problems with the
logic board, though getting the beep makes this sound less likely.
If the monitor itself is the problem, I remember reading in some issues of
"FOGHORN" years back that there were certain capacitors in the monitor
assembly that would cause problems, though I don't remember which ones they
were.
The monitor itself was apparently made by Zenith, but I have not yet been
able to locate a schematic for that portion of things, though I have
complete tech info on the rest of the computer. If anybody knows where I
might find a schematic of the monitor as well I'd sure like to hear about 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
13 Feb
13 Feb
8:12 p.m.
The monitor itself was apparently made by Zenith, but
I have not yet been
able to locate a schematic for that portion of things, though I have
complete tech info on the rest of the computer. If anybody knows where I
might find a schematic of the monitor as well I'd sure like to hear about it.
How hard would it be to trace out a schematic? OK, Zenith often used
house-coded ICs which will make things slightly more difficult, but at
least they're not custom ICs so they can be identified in the end. I
can't believe a small mono monitor is _that_ complicated.
-tony
14 Feb
14 Feb
12:54 p.m.
Tony Duell wrote:
Both Dave and Roy now have the Monitor schematics for the Exec.
It is all discrete components.
The monitor itself was apparently made by Zenith,
but I have not yet been
able to locate a schematic for that portion of things, though I have
complete tech info on the rest of the computer. If anybody knows where I
might find a schematic of the monitor as well I'd sure like to hear about it.
How hard would it be to trace out a schematic? OK, Zenith often used
house-coded ICs which will make things slightly more difficult, but at
least they're not custom ICs so they can be identified in the end. I
can't believe a small mono monitor is _that_ complicated.
-tony
1:23 p.m.
On Tuesday 14 February 2006 03:54 pm, John C. Ellingboe wrote:
Tony Duell wrote:
Both Dave and Roy now have the Monitor schematics for the Exec.
It is all discrete components.
Yup! They got here just fine...
And if anybody is working on any Osborne, Kaypro, or C64 stuff feel free to
give a holler as I did quite a bit of that and have tech info available if I
need it. And lots of parts, particularly for the c64 stuff (although I
could use a mess of SID chips if anybody has any units I could scrap for
them).
--
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
The
monitor itself was apparently made by Zenith, but I have not yet
been able to locate a schematic for that portion of things, though I
have complete tech info on the rest of the computer. If anybody knows
where I might find a schematic of the monitor as well I'd sure like to
hear about it.
How hard would it be to trace out a schematic? OK, Zenith often used
house-coded ICs which will make things slightly more difficult, but at
least they're not custom ICs so they can be identified in the end. I
can't believe a small mono monitor is _that_ complicated.
-tony
13 Feb
13 Feb
10:30 p.m.
And if anybody is working on any Osborne, Kaypro, or C64 stuff feel free to
give a holler as I did quite a bit of that and have tech info available if I
I don;'t suppose you know anything about the Sony CX065B chip, do you?
It's a motor speed controller, and I'm doing battle with it (and other
components) in the spindle motor of an Epson SD320 drive, used in a TF20.
I have the service information on the SD321 drive (same unit without a
head load solenoid) in the QX10 techical mnaul, but it doesn't really
explain this chip at all.
The reason I ask here is that I've discovered the same chip was used in
the Alps drive mechanism used in the Commodore 1504 and 1541. I have the
offical CBM serivce manual which contains a scheamtic and little else, I
also have the Sams book on repairing said units which contains rather
more information. I wondered if you had anything else?
-tony
14 Feb
14 Feb
3:46 p.m.
On Tuesday 14 February 2006 01:30 am, Tony Duell wrote:
That number doesn't ring any bells offhand. A quick search on the number
doesn't turn anything up.
And if anybody
is working on any Osborne, Kaypro, or C64 stuff feel free
to give a holler as I did quite a bit of that and have tech info
available if I
I don;'t suppose you know anything about the Sony CX065B chip, do you? It's a motor speed controller, and I'm doing
battle with it (and other
components) in the spindle motor of an Epson SD320 drive, used in a TF20.
I have the service information on the SD321 drive (same unit without a
head load solenoid) in the QX10 techical mnaul, but it doesn't really
explain this chip at all.
The reason I ask here is that I've discovered the same chip was used in
the Alps drive mechanism used in the Commodore 1504 and 1541. I have the
offical CBM serivce manual which contains a scheamtic and little else, I
also have the Sams book on repairing said units which contains rather
more information. I wondered if you had anything else?
Not offhand. The only time I ever really encountered any serious speed
problems with those motors was when the tach winding opened up, and they'd
run at full-speed with no regulation. I do have the manuals for the 1541 in
the other room, and can take a look...
I have had speed control chips fail on a small number of occasions, but don't
recall whether this was one of the numbers or not. Usually if you're
getting a good waveform off the tach winding and power to the chip, and no
control coming out, that's the problem -- it's been either the motor or the
chip in those cases, not much else in there.
What sort of a problem are you having?
--
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
4:06 p.m.
The Epson motor is very different to the Commodore one. Commodore used a
permanent magnet DC motor, the Epson drive uses a 4 phase motor with
electronic commutation (there are 2 hall sensors under the PCB). It's
just the speed controller chip that's the same/
Not offhand. The only time I ever really encountered
any serious speed
problems with those motors was when the tach winding opened up, and they'd
That problem I've got. I've taken the motor housing apart, and have tried
to repair the coil. Time will tell...
run at full-speed with no regulation. I do have the
manuals for the 1541 in
the other room, and can take a look...
I have the ofifical Commodore manual, so if that's what you have there's
no need for you to look.
I have had speed control chips fail on a small number of occasions, but don't
recall whether this was one of the numbers or not. Usually if you're
getting a good waveform off the tach winding and power to the chip, and no
control coming out, that's the problem -- it's been either the motor or the
Sure...
chip in those cases, not much else in there.
See above, the Epson motor is a lot more complicated. There's the chip
and 10 discrete transistors on the PCB.
For interest I'd like to know exactly what the chip does (I am curious
like that...). I'd also like to know just what the 'other' preset on the
Epson board is for (not the one that sets the speed), it seems to balance
the 2 hall sensors or something like that.
What sort of a problem are you having?
Initially an open FG coil, let's hope I can get that right...
-tony
24 Feb
24 Feb
8:04 a.m.
New subject: CX065B again (was Re: Osborne Executive CRT circuitry)
Tony --
After a little digging I found a datasheet for
the NTE replacement for CX065B in PDF format.
If you'd like I can email it to you or print it
out and snail-mail it.
Glen
0/0
Tony Duell wrote:
The Epson motor is very different to the Commodore
one. Commodore used a
permanent magnet DC motor, the Epson drive uses a 4 phase motor with
electronic commutation (there are 2 hall sensors under the PCB). It's
just the speed controller chip that's the same/
Not offhand. The only time I ever really
encountered any serious speed
problems with those motors was when the tach winding opened up, and they'd
That problem I've got. I've taken the motor housing apart, and have tried
to repair the coil. Time will tell...
run at full-speed with no regulation. I do have
the manuals for the 1541 in
the other room, and can take a look...
I have the ofifical Commodore manual, so if that's what you have there's
no need for you to look.
I have had speed control chips fail on a small
number of occasions, but don't
recall whether this was one of the numbers or not. Usually if you're
getting a good waveform off the tach winding and power to the chip, and no
control coming out, that's the problem -- it's been either the motor or the
Sure...
chip in those cases, not much else in there.
See above, the Epson motor is a lot more complicated. There's the chip
and 10 discrete transistors on the PCB.
For interest I'd like to know exactly what the chip does (I am curious
like that...). I'd also like to know just what the 'other' preset on the
Epson board is for (not the one that sets the speed), it seems to balance
the 2 hall sensors or something like that.
What sort of a problem are you having?
Initially an open FG coil, let's hope I can get that right...
-tony
7:58 a.m.
New subject: CX065B (was Re: Osborne Executive CRT circuitry)
Hi Tony --
Well, I couldn't find the datasheet for this IC
but I did locate a few of them if you need 'em
(I deal in Japanese semiconductors for the consumer
electronics repair trade).
Glen
0/0
Roy J. Tellason wrote:
On Tuesday 14 February 2006 01:30 am, Tony Duell
wrote:
That number doesn't ring any bells offhand. A quick search on the number
doesn't turn anything up.
And if
anybody is working on any Osborne, Kaypro, or C64 stuff feel free
to give a holler as I did quite a bit of that and have tech info
available if I
I don;'t suppose you know anything about the Sony CX065B chip, do you?
4:19 p.m.
New subject: CX065B (was Re: Osborne Executive CRT circuitry)
Hi Tony --
Well, I couldn't find the datasheet for this IC
but I did locate a few of them if you need 'em
(I deal in Japanese semiconductors for the consumer
electronics repair trade).
Well, I finally got the thing to work (based mostly on the info in the
SAMS book on the 1541 [1]) And it was quite a job.
[1] I bought this in a second-hand bookshop in Bristol over 10 years ago.
I am not much of a Commodore person, but I always buy old computer books
that contain schematics...
Anyway, back to the Epson disk drive story. The drive I'm working on is
an SD320, used in the TF20 drive unit for the HX20/PX8/PX4 laptops. If
you want to follow along, I think the techncial manual for the QX10 is on
the web somewhere. This machine uses SD321 drives. The difference is that
the SD320 ahs a head load solenoid, the SD321 doesn't. Otherwise they are
almost identical (the positioner, spidle motor, and most of the
mechnaical parts are the same. There are small differences on the main PCB
(as to which components are fitted), but it's the same board, same ASICs,
etc.
So the scheamtic of the spindle motor in the QX10 manual will help.
OK, it's a farily simple design. There's a 4 pole stator with a rotor
around it. The inside of the rotor has a pair of permanent magnets on it.
These are pulled round by the stator coils, they also trigger a pair of
hall sensors on the PCB, which control transistors that drive the windings.
Inside the housing, on top of the rotor, is the FG (frequency generator)
coil. This produces an AC signal, the frequency of which depends on the
speed of the motr. This is fed to the CX065B chip, the output of that
controls the motor drive amplifier. If the motor is running too slowly,
the output voltage of the CX065B increases, making the amplifier drive
the coils harder.
So far so good. Anyway, I had the motor out of the drive (I needed to
clean the old greae off the eject linkages...). I was pretty sure I knew
how it was used. so I linked up the 3 pins on the connector to a 12V
bench supply (motor enable anf ground to -ve, 12v to +ve). The result was
that the motor started, ran for a few seconds, and stopped.
OK, I thought, a faulty motor. So I tried the one in the other drive. It
did the same thing. I even pulled a drive from my 'spare' QX10 and tried
the motor from that. It did the same thing.
So I thohght that perhaps the enable line wasn't just a DC voltage --
ground to enable. Maybe it was some kind of clock input.. So I put a
drive back together, cabled it up to a drive exerciser, and tried again.
You guessed it, motor runs for a few seconds and stops. And the signal on
the enable pin is just a DC voltage, it's pulled to ground when the motor
should be running.
So I investigated the motor further. And discover the transistor Q23 on
the schematic. Its purpose is to stop the motor if the output from the
CX065B rises too high. It'll do that if either the FG signal is missing
(so the CX065B thinks the motor isn't turning at all), or if the motor is
overloaded, so the CX065B has to drive it harder.
The only prroblem is that if the bearings get a bit stiff, this circuit
triggers too easily. Replaceing the bearings is a right pain (I know
_how_ to do it, but you almost always damage the FG coil and have to
unwind at least one turn and then reassemble that part, etc). There's an
ARD-unofficial-kludge, though. There's a 75k (100k on some drives)
resistor on the motor PCB, near to the connector and at right angles to
it. Reduce that a bit (68k, 56k). This makes the protection circuit a bit
harder to trigger (but it will still trigger if the motor is stalled).
Moral : If 3 identical old computer parts appear to malfunction in the
same way, they might all be faulty!
-tony
14 Feb
14 Feb
12:56 p.m.
On Monday 13 February 2006 11:12 pm, Tony Duell wrote:
Well, since around the time we closed up our shop (April of 1992) I've been
having to use a lighted magnifier to be able to see stuff that I was able to
deal with quite nicely before, I'm not up to it. Sucks, but there it is,
and I just deal with it.
You'd also need to remove some of the stuff from the assembly, which is
pretty tight.
And, shining a strong light through the boards to see where traces go etc. is
complicated by the fact that Zenith used blobs of hot glue to hold the
bulkier components in place, including a lot of the caps, TO220
transistors, etc.
I once tried to acquire a schematic from Zenith, since we were a ZDS service
center at the time, but apparently ZDS knew nothing about this side of
things, and I wasn't successful. I imagine that info has to be out there
somewhere.
--
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
The monitor
itself was apparently made by Zenith, but I have not yet
been able to locate a schematic for that portion of things, though I
have complete tech info on the rest of the computer. If anybody knows
where I might find a schematic of the monitor as well I'd sure like to
hear about it.
How hard would it be to trace out a schematic? OK, Zenith often used
house-coded ICs which will make things slightly more difficult, but at
least they're not custom ICs so they can be identified in the end. I
can't believe a small mono monitor is _that_ complicated.
13 Feb
13 Feb
10:24 p.m.
Well, since around the time we closed up our shop
(April of 1992) I've been
having to use a lighted magnifier to be able to see stuff that I was able to
deal with quite nicely before, I'm not up to it. Sucks, but there it is,
and I just deal with it.
I didn't necessarily mean that _you_ should do it. There must be other
people with that machine (amazingly, I don't own any CP/M luggables yet...)
You'd also need to remove some of the stuff from the assembly, which is
pretty tight.
And, shining a strong light through the boards to see where traces go etc. is
complicated by the fact that Zenith used blobs of hot glue to hold the
bulkier components in place, including a lot of the caps, TO220
transistors, etc.
I'd not do it that way. What I'd do is desolder any components that would
test as a short-circuit (fuses, low-value resistors, inductors,
transformers), and use a continuity tester to check where things go. I've
done this many times on monitors and PSUs and never had any problems.
Incidentally, if that glue is like the stuff we get in TV sets over here,
it goes conductive with age (!). It causes all sorts of interesting faults...
-tony
14 Feb
14 Feb
3:30 p.m.
On Tuesday 14 February 2006 01:24 am, Tony Duell wrote:
Incidentally, if that glue is like the stuff we get in
TV sets over here,
it goes conductive with age (!). It causes all sorts of interesting
faults...
I've heard that, that this is the case with whatever the goop is that
Japanese mfrs. use for stuff like holding down large capacitors, etc. And
that it starts out as a light brown in color, turning very dark as it ages.
The stuff I was referring to is off-white (milky-looking) and quite hard when
it's set, which makes it interesting to remove components.
--
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
1:36 p.m.
I've heard that, that this is the case with
whatever the goop is that
Japanese mfrs. use for stuff like holding down large capacitors, etc. And
that it starts out as a light brown in color, turning very dark as it ages.
The stuff I was referring to is off-white (milky-looking) and quite hard when
it's set, which makes it interesting to remove components.
--
Yes it is the stuff. Seems this particular glue found in low
quality stuff.
Fresh stuff is very TOUGH to cut through and hard to rip apart,
baked, crispy-black & conductive.
Cheers, WIzard
12:59 p.m.
On Tue, 14 Feb 2006, Tony Duell wrote:
I've acquired schematics for the CRT subsection. All the ICs used are
74ls series logic. I think I have what I need to do some meaningful
diagnosis. I'll follow up when I get the time to sit down and fiddle with
the machine.
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
The monitor
itself was apparently made by Zenith, but I have not yet
been able to locate a schematic for that portion of things, though I
have complete tech info on the rest of the computer. If anybody knows
where I might find a schematic of the monitor as well I'd sure like to
hear about it.
How hard would it be to trace out a schematic? OK, Zenith often used
house-coded ICs which will make things slightly more difficult, but at
least they're not custom ICs so they can be identified in the end. I
can't believe a small mono monitor is _that_ complicated. 
12:13 p.m.
On Tue, 14 Feb 2006 14:35:09 -0500, Roy J. Tellason wrote:
On Monday 13 February 2006 02:34 pm, David Griffith
wrote:
this should be the right one if the sold exceutive in germany ist
identical.-)
For the foghorn I must have to search.
http://oldcomputers.dyndns.org/public/pub/rechner/osborne/executiv/manua
l/sheets/osbe_video.png
Here ist other
http://oldcomputers.dyndns.org/public/pub/rechner/osborne/executiv/
Mit freundlichen Gruessen
Fritz Chwolka
I'm trying to restore an Osborne Executive,
but there seems to be
something wrong in the CRT circuitry. The machine powers up and beeps,
If the monitor itself is the problem, I remember reading in some issues of
"FOGHORN" years back that there were certain capacitors in the monitor
assembly that would cause problems, though I don't remember which ones they
were.
The monitor itself was apparently made by Zenith, but I have not yet been
able to locate a schematic for that portion of things, though I have
complete tech info on the rest of the computer. If anybody knows where I
might find a schematic of the monitor as well I'd sure like to hear about it.
6874
days inactive
6886
days old
24 comments
11 participants
participants (11)
-
acme_ent＠bellsouth.net -
arcarlini＠iee.org -
ard＠p850ug1.demon.co.uk -
cfox1＠cogeco.ca -
dave04a＠dunfield.com -
dgriffi＠cs.csubak.edu -
fritz_chwolka＠t-online.de -
john＠guntersville.net -
jpero＠sympatico.ca -
mloewen＠cpumagic.scol.pa.us -
rtellason＠blazenet.net