8 May
2010
8 May
'10
2:33 a.m.
Chris,
I have the monitor listing (v 2.1) for the SDK-85 in digital form if it
will help.
I've modified it to compile with Pseudo Sam by removing the macros.
I've added line drivers (75188 and 75189) to my SDK-85 to support
RS-232C and changed the code so it runs at 9600 baud.
If you can rustle up an 8755 you could burn the monitor to it.
Regards,
Carl
--
Carl Allen
Plus! Computers, Inc.
(336) 659-8549
tech at pluscomputers.com
www.pluscomputers.com
--
8 May
8 May
7:22 a.m.
Thank you Carl. I did receive a .BIN file of the monitor a while ago
and just recently got it burned into an 8755A. Unfortunately, this has
not fixed the problem-- or, rather, introduced a new problem as the
little machine still does not run at all (frozen or not) with the new
EPROM resident monitor.
So, there is something a little more sinister going on here. Still
investigating...
Chris
On Saturday (05/08/2010 at 02:33AM -0400), Carl Allen wrote:
Chris,
I have the monitor listing (v 2.1) for the SDK-85 in digital form if it
will help.
I've modified it to compile with Pseudo Sam by removing the macros.
I've added line drivers (75188 and 75189) to my SDK-85 to support
RS-232C and changed the code so it runs at 9600 baud.
If you can rustle up an 8755 you could burn the monitor to it.
Regards,
Carl
--
Carl Allen
Plus! Computers, Inc.
(336) 659-8549
tech at pluscomputers.com
www.pluscomputers.com
--
Chris Elmquist
10 May
10 May
10:18 a.m.
Hi
As was mentioned, there is a different pin on the 8755A than
the 8355 used on the sdk85. Did you check that it was
at the correct level?
Dwight
From: chrise at pobox.com
To: cctech at classiccmp.org
Subject: Re: i8355 from SDK-85 flakey
Thank you Carl. I did receive a .BIN file of the monitor a while ago
and just recently got it burned into an 8755A. Unfortunately, this has
not fixed the problem-- or, rather, introduced a new problem as the
little machine still does not run at all (frozen or not) with the new
EPROM resident monitor.
So, there is something a little more sinister going on here. Still
investigating...
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11:17 a.m.
On Monday (05/10/2010 at 07:18AM -0700), dwight elvey wrote:
Hi
As was mentioned, there is a different pin on the 8755A than
the 8355 used on the sdk85. Did you check that it was
at the correct level?
Yes... there are several jumper pads on the PCB which you strap differently
whether there is an 8355, 8755 or 8755A in the socket. I strapped for 8755A,
which is what I am using. No joy.
I'm suspecting a micro-fine crack in a PCB trace as the next culprit so I
will soon get back to looking for that.
Chris
--
Chris Elmquist
5:14 p.m.
Hi Chris
A good way to look for such opens ( usually of feed thrus ) is to use a
two input scope and combine both inputs with one of them inverted.
Check the easy ones first, like address and data lines.
Even a non-active line will show a difference in voltage when probed
this way. I've used this on a couple of trouble cases with good
results.
Dwight
Date: Mon, 10 May 2010 10:17:46 -0500
From: chrise at pobox.com
To: cctech at classiccmp.org
Subject: Re: i8355 from SDK-85 flakey
CC: cctalk at classiccmp.org
On Monday (05/10/2010 at 07:18AM -0700), dwight elvey wrote:
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Hi
As was mentioned, there is a different pin on the 8755A than
the 8355 used on the sdk85. Did you check that it was
at the correct level?
Yes... there are several jumper pads on the PCB which you strap differently
whether there is an 8355, 8755 or 8755A in the socket. I strapped for 8755A,
which is what I am using. No joy.
I'm suspecting a micro-fine crack in a PCB trace as the next culprit so I
will soon get back to looking for that.
Chris
--
Chris Elmquist
11 May
11 May
12:51 p.m.
On Monday (05/10/2010 at 02:14PM -0700), dwight elvey wrote:
Hi Chris
A good way to look for such opens ( usually of feed thrus ) is to use a
two input scope and combine both inputs with one of them inverted.
Check the easy ones first, like address and data lines.
Even a non-active line will show a difference in voltage when probed
this way. I've used this on a couple of trouble cases with good
results.
Good tip Dwight. Thanks.
--
Chris Elmquist
7:12 p.m.
From: ard at p850ug1.demon.co.uk
Subject: Re: i8355 from SDK-85 flakey
To: cctalk at classiccmp.org
Date: Tue, 11 May 2010 21:38:16 +0100
Hi Tony
With an ohmmeter, it is often difficult to know when the contact is good.
Many times I've seen problems with bad sockets that looked good on the
ohmmeter because I pressed the lead of the IC hard to ensure good contact.
With a scope, you can see visually that the contact is good enough and that no
additional pressure is needed. I don't need a low ohms contact with the
scope lead. A less than optimal contact is usually good enough( especially with
a 10X probe ).
It is also a little faster, especially when running down address or bus leads.
I do use a meter often as well. Once I locate a suspect trace, I use the
meter to pin it down.
Dwight
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Hi Chris
A good way to look for such opens ( usually of feed thrus ) is to use a
two input scope and combine both inputs with one of them inverted.
Check the easy ones first=2C like address and data lines.
How is this better than using a good ohmmeter (with the power off)?
-tony 
12 May
12 May
2:02 p.m.
Many times I've seen problems with bad sockets
that looked good on the
ohmmeter because I pressed the lead of the IC hard to ensure good contact.
With a scope=2C you can see visually that the contact is good enough and th=
at no
additional pressure is needed. I don't need a low ohms contact with the
scope lead. A less than optimal contact is usually good enough( especially =
with
a 10X probe ).
OK, got you. It's almost doing a 4-terminal mesuremtn where the current
is supplied by the device under test, and the 'scope is the votlage
detector. As you said, assuming a reasonable input impedance on the
'scope, a poor contact at the probe tip won't matter much.
-tony
10 May
10 May
1:18 p.m.
I can attest to a flakiness of the SDK-85 operation if the pin is not properly selected.
My board had a 8355 and it failed. I replaced it with a 8755A and it was flakey because I
did not change the ROM pin select. After correctly connecting the ROM pin, all worked
fine. I have a SDK board and the manuals if you need any information.
J
---- dwight elvey <dkelvey at hotmail.com> wrote:
Hi
As was mentioned, there is a different pin on the 8755A than
the 8355 used on the sdk85. Did you check that it was
at the correct level?
Dwight
From: chrise at pobox.com
To: cctech at classiccmp.org
Subject: Re: i8355 from SDK-85 flakey
Thank you Carl. I did receive a .BIN file of the monitor a while ago
and just recently got it burned into an 8755A. Unfortunately, this has
not fixed the problem-- or, rather, introduced a new problem as the
little machine still does not run at all (frozen or not) with the new
EPROM resident monitor.
So, there is something a little more sinister going on here. Still
investigating...
_________________________________________________________________
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2:36 p.m.
Thank you Carl. I did receive a .BIN file of the monitor a while ago
and just recently got it burned into an 8755A. Unfortunately, this has
not fixed the problem-- or, rather, introduced a new problem as the
little machine still does not run at all (frozen or not) with the new
EPROM resident monitor.
So, there is something a little more sinister going on here. Still
investigating...
Assuming you've not made a mistake programming the 8755, and that the
8755 is not defective, have you checked the state of pin 5? It's N/C on
the 8355, and Vpp on the 8755. There's a link on the SDK-85 board
associated with this pin. You might check that.
If you put the original monitor ROM in its socket and put the 8755 in the
ROM extension socket, can you read out the nrwly-programmed EPROM at the
extension ROM location?
-tony
11 May
11 May
12:47 p.m.
On Monday (05/10/2010 at 07:36PM +0100), Tony Duell wrote:
Yes. Thanks. I've set the jumper according to the manual's instructions
for an 8755A at location A14. The setup sure appears correct.
Thank you Carl. I did receive a .BIN file of the monitor a while ago
and just recently got it burned into an 8755A. Unfortunately, this has
not fixed the problem-- or, rather, introduced a new problem as the
little machine still does not run at all (frozen or not) with the new
EPROM resident monitor.
So, there is something a little more sinister going on here. Still
investigating...
Assuming you've not made a mistake programming the 8755, and that the
8755 is not defective, have you checked the state of pin 5? It's N/C on
the 8355, and Vpp on the 8755. There's a link on the SDK-85 board
associated with this pin. You might check that. If you put the original monitor ROM in its socket and
put the 8755 in the
ROM extension socket, can you read out the nrwly-programmed EPROM at the
extension ROM location?
That's on the ToDo list. Unfortunately the ROM extension location at A15
has no socket installed and all the holes are flowed over with solder. So
I need to carefully solder-suck, solder-wick those clean before I can
install a socket. Boards of this age are quite fond of letting the pads
loose when you heat them up so I need to do this slowly and carefully.
And thanks to the other poster that offered a manual. I have all of that
so I am set documentation-wise.
Chris
--
Chris Elmquist
12 May
12 May
1:47 p.m.
That's on the ToDo list. Unfortunately the ROM
extension location at A15
has no socket installed and all the holes are flowed over with solder. So
The PCB was probably wave-soldered with no socket in place. Seems
strange, on an experimental machine like this not to fit the expansion
socckets, but anyway...
I need to carefully solder-suck, solder-wick those
clean before I can
install a socket. Boards of this age are quite fond of letting the pads
loose when you heat them up so I need to do this slowly and carefully.
The best way I've found to do this is to hold or clamp the board
vertically, melt th solder with an iron on one side and suck with a
solder sucker from the other. It's not too bad doing it for a 40 pin
socket, it gets boring fast when you have to clear out 16 or 32 16 pin
locations for a memory upgrade (been there, done that, don't wear
t-shirts ;-))
-tony
8:58 p.m.
On Wednesday (05/12/2010 at 06:47PM +0100), Tony Duell wrote:
yes... and to make matters worse, some of the devices were soldered
in without sockets too! I first suspected the 8279 display+keypad
controller and so I had to sacrifice it by cutting the pins off the
package and then desoldering each pin one at a time. Sadly, that did
not fix the problem and I wasted a nice ceramic packaged 8279 circa 1976.
This board likely had a different history than other SDK-85 since it
was built into this Philips logic analyzer demo system. It's possible
Philips bought the boards assembled from Intel or some middleman who
assembled them in this static configuration.
yes... or shorts. Do you call them shorts over there? aka, short pants.
I still have the scars on my leg from dropping solder blobs onto them
while wearing shorts at the bench as a kid. Not cool.
--
Chris Elmquist
That's on the ToDo list. Unfortunately the
ROM extension location at A15
has no socket installed and all the holes are flowed over with solder. So
The PCB was probably wave-soldered with no socket in place. Seems
strange, on an experimental machine like this not to fit the expansion
socckets, but anyway... I need to
carefully solder-suck, solder-wick those clean before I can
install a socket. Boards of this age are quite fond of letting the pads
loose when you heat them up so I need to do this slowly and carefully.
The best way I've found to do this is to hold or clamp the board
vertically, melt th solder with an iron on one side and suck with a
solder sucker from the other. It's not too bad doing it for a 40 pin
socket, it gets boring fast when you have to clear out 16 or 32 16 pin
locations for a memory upgrade (been there, done that, don't wear
t-shirts ;-))
13 May
13 May
1:16 p.m.
New subject: i8355 from SDK-85 flakey [SOLVED]
Well, we can put a bow on this one now. I've found the problem.
Turns out there was a damaged via on pin 40 of A15 (the optional ROM
location) that provides +5 to pin 8 of A14 (the monitor ROM socket).
The result was that pin 8 was floating. Pin 8 of 8355 or 8755 is I/OR-
and is not used in this design (as I/OM- and RD- are used instead) and
so needs to be tied high. With it floating, it was randomly gating an
I/O read onto the bus I suppose. When I was freezing the part, I was
obviously changing the switch point and causing it to mostly be high
instead of sitting at or below threshold.
The via was likely damaged when they made mods to the board for the
Philips logic analyzer demo application.
So, now both the 8355 and the 8755A work.
Nothing sinister going on _inside_ the devices after all ;-)
Thanks to all for playing along.
Chris
On Wednesday (05/12/2010 at 07:58PM -0500), Chris Elmquist wrote:
On Wednesday (05/12/2010 at 06:47PM +0100), Tony Duell
wrote:
yes... and to make matters worse, some of the devices were soldered
in without sockets too! I first suspected the 8279 display+keypad
controller and so I had to sacrifice it by cutting the pins off the
package and then desoldering each pin one at a time. Sadly, that did
not fix the problem and I wasted a nice ceramic packaged 8279 circa 1976.
This board likely had a different history than other SDK-85 since it
was built into this Philips logic analyzer demo system. It's possible
Philips bought the boards assembled from Intel or some middleman who
assembled them in this static configuration.
yes... or shorts. Do you call them shorts over there? aka, short pants.
I still have the scars on my leg from dropping solder blobs onto them
while wearing shorts at the bench as a kid. Not cool.
--
Chris Elmquist
--
Chris Elmquist
That's on the ToDo list. Unfortunately the
ROM extension location at A15
has no socket installed and all the holes are flowed over with solder. So
The PCB was probably wave-soldered with no socket in place. Seems
strange, on an experimental machine like this not to fit the expansion
socckets, but anyway... I need to
carefully solder-suck, solder-wick those clean before I can
install a socket. Boards of this age are quite fond of letting the pads
loose when you heat them up so I need to do this slowly and carefully.
The best way I've found to do this is to hold or clamp the board
vertically, melt th solder with an iron on one side and suck with a
solder sucker from the other. It's not too bad doing it for a 40 pin
socket, it gets boring fast when you have to clear out 16 or 32 16 pin
locations for a memory upgrade (been there, done that, don't wear
t-shirts ;-)) 
16 May
16 May
2:55 p.m.
New subject: i8355 from SDK-85 flakey [SOLVED]
On 5/13/10 1:16 PM, Chris Elmquist wrote:
Well, we can put a bow on this one now. I've
found the problem.
Turns out there was a damaged via on pin 40 of A15 (the optional ROM
location) that provides +5 to pin 8 of A14 (the monitor ROM socket).
The result was that pin 8 was floating. Pin 8 of 8355 or 8755 is I/OR-
and is not used in this design (as I/OM- and RD- are used instead) and
so needs to be tied high. With it floating, it was randomly gating an
I/O read onto the bus I suppose. When I was freezing the part, I was
obviously changing the switch point and causing it to mostly be high
instead of sitting at or below threshold.
The via was likely damaged when they made mods to the board for the
Philips logic analyzer demo application.
So, now both the 8355 and the 8755A work.
Nothing sinister going on _inside_ the devices after all ;-)
Thanks to all for playing along.
Great catch, congrats!
-Dave
--
Dave McGuire
Port Charlotte, FL
2:39 p.m.
On Wednesday (05/12/2010 at 06:47PM +0100), Tony Duell wrote:
yes... and to make matters worse, some of the devices were soldered
in without sockets too! I first suspected the 8279 display+keypad
Pity...
That's on the ToDo list. Unfortunately the
ROM extension location at A15
has no socket installed and all the holes are flowed over with solder. So
The PCB was probably wave-soldered with no socket in place. Seems
strange, on an experimental machine like this not to fit the expansion
socckets, but anyway... controller and so I had to sacrifice it by cutting the
pins off the
package and then desoldering each pin one at a time. Sadly, that did
not fix the problem and I wasted a nice ceramic packaged 8279 circa 1976.
Normally I find I can desolder the device and sae both the chip and the
PCB. I think I've mentioned before that the trick is, after sucking off
the solder, to use a small flat-blade screwdriver on the component side
to puse each pin towards the IC body and break the remaing solder bond.
A couple of times I have had to cut off the pins. I've found that with a
good pair of close-cutting end nippers you can leave enough of a stub on
the package to then be able to solder the device to the top of a normal
DIL socket which yo ucan then plug into another DIL socket to use it. I
wouldn't trust it in somebody else's machine unless I _had_ to, but I've
savaged a dew hard-to-get ICs that way.
The best way I've found to do this is to hold or clamp the board
vertically, melt th solder with an iron on one side and suck with a
solder sucker from the other. It's not too bad doing it for a 40 pin
socket, it gets boring fast when you have to clear out 16 or 32 16 pin
locations for a memory upgrade (been there, done that, don't wear
t-shirts ;-))
yes... or shorts. Do you call them shorts over there?
aka, short pants.
Yes 'shorts' has the same meaning over here. But 'pants' tends to refer
to underwear.
I still have the scars on my leg from dropping solder
blobs onto them
while wearing shorts at the bench as a kid. Not cool.
Ouch. I can still just see the burn on the back of my hand where I
dropped solder on it <mumble> years ago...
-tony
6:23 p.m.
On 16/05/10 19:39, Tony Duell wrote:
Ouch. I can still just see the burn on the back of my
hand where I
dropped solder on it<mumble> years ago...
I've got one on my right arm from leaning over the hot end of a hot-air
soldering station while it was 'live'. The display read "COOLING: 40 C,
but it turns out that was the setpoint, not the current temperature. Hot
air burns HURT LIKE HELL. Didn't look like much at the time, but 9
months down the line I still have the scars.
Then there's the mark on the back of my right hand from where the
tinsnips fell off the hook above the door as I was leaving the shed.
That almost completely umbed my hand for a good hour or two...
I've also done "picking up the soldering iron from the wrong end", and
I've had one or two mains plugs with duff screw inserts -- the entire
back of one of the plugs shattered when I tried to unplug it, allowing
the palm of my hand to form a very nice low-resistance path over the
phase and neutral lines. Bzzzzzkt! One of the many things neither a
13-amp plug fuse or an RCD (RCCB) circuit breaker will protect you from.
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
17 May
17 May
3:26 p.m.
I've got one on my right arm from leaning over the
hot end of a hot-air
soldering station while it was 'live'. The display read "COOLING: 40 C,
but it turns out that was the setpoint, not the current temperature. Hot
air burns HURT LIKE HELL. Didn't look like much at the time, but 9
months down the line I still have the scars.
I am going to have to get a hot-air soldering station. Problem i, the
good ones are too expensive, and the cheap ones are not good (and don't
have adequate spares backup). Oh well, one day...
I've also done "picking up the soldering iron
from the wrong end", and
I had some idiot trip over the mains lead of my soldering iron (cheap,
mains-powered iron) at school. Pulled the iron back through my hand so I
was gripping it by the metal element shaft. Ouch!
I've had one or two mains plugs with duff screw
inserts -- the entire
back of one of the plugs shattered when I tried to unplug it, allowing
I have found that MK brand (and Duraplug for rubber plugs) don't have
this problem. And those are all I use now.
the palm of my hand to form a very nice low-resistance
path over the
phase and neutral lines. Bzzzzzkt! One of the many things neither a
13-amp plug fuse or an RCD (RCCB) circuit breaker will protect you from.
Yes, but a live-neutral connection through the fingers of one hand is
unlikely to kill you, thankfully.
I once (accidentally) started reassembling a device without unplugging it
from the mains. When picking up the rear panel, my
fingers touched the
back of the mains fuseholder which was live. Fortunately the
panel was
soildly earhted, so as in your case the current only passed through that
hand. Ouch, but I am here to tell you about it.
-tony
16 May
16 May
2:53 p.m.
On 5/12/10 8:58 PM, Chris Elmquist wrote:
yes... and to make matters worse, some of the devices
were soldered
in without sockets too! I first suspected the 8279 display+keypad
controller and so I had to sacrifice it by cutting the pins off the
package and then desoldering each pin one at a time. Sadly, that did
not fix the problem and I wasted a nice ceramic packaged 8279 circa 1976.
Oh that SUCKS...Ceramic-packaged 8279s are, in my experience,
extremely rare. :-(
-Dave
--
Dave McGuire
Port Charlotte, FL
5154
days inactive
5163
days old
19 comments
7 participants
participants (7)
-
ard＠p850ug1.demon.co.uk -
chrise＠pobox.com -
classiccmp＠philpem.me.uk -
dkelvey＠hotmail.com -
jelynch＠stny.rr.com -
mcguire＠neurotica.com -
tech＠pluscomputers.com