I found Digital Technical Journal Volume 8 Number 3 which contains the subject article title by Burnet and Supnik. If they are on this list and approve it, I will scan this in and make it available.
Just out of curiosity, I am wondering... Did anyone here manage to
score those Cromemco systems I mentioned a couple months ago that
ended up being sent to Re-PC in Seattle? Just hoping that they found
a good home. :)
-- Scarletdown
I have had success in the past using a folded piece of paper (many times) to
chock the broken simm.
It may work, but it's a *really* messy solution
Doug Jackson
Director, Managed Security Services
Citadel Securix
+61 (0)2 6290 9011 (Ph)
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Web: <www.citadel.com.au>
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-----Original Message-----
From: Bob Lafleur [mailto:bob_lafleur@technologist.com]
Sent: Friday, November 15, 2002 4:26 PM
To: cctalk(a)classiccmp.org
Subject: Broken SIMM tabs on Mac IIci
Ok, so I did it... When trying to remove the SIMMS in my Mac IIci I broke
some of the little tiny plastic tabs, so now the new SIMMs won't lock in.
Is there some "fix" to get the SIMMs to stay in, short of soldering new
sockets into the board (which I am not about to do)?
Also, I broke them on Bank A. I assume you can't use RAM in Bank B without
having Bank A full...
Should I just trash the motherboard? Or can I salvage it somehow?
Are these SIMM tabs particularly vulnerable, especially on this old
equipment? I broke them on 2 machines, and on the 2nd one I did, I was
trying to be very careful.
- Bob
(not a happy MACer today)
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I consolidated Tony's and Dwight's comments onto one
post... thanks to both for your comments so far.
>Ah... Do you hapeen to know if the original position
of the brush holder
>was way out? If so, then it's possible the previous
owner tried to
>compensate for that using the 'rangefinder'
adjustment on the RX module
>(the slider + scale near the receiving magnet). Have
you treid the affect
>of this adjustment?
I tweaked this last night to see what would happen,
but there was no improvement. But it was an
interesting exercise anyway.
>You can elminiate the keyboard by trying the reader.
If the reader works
>perdectly, then the keyboard must be the problem. My
guess is that it
>won't, though. You can open the tope of the rrrreader
and hold the tape
>sensor down by hand. That will read continual
Rubouts. Or hold down some
>the pins too to get different characters. Of course
if you have some
>correctly punched tape, use that.
Good idea - I re-connected the reader and tried it.
The codebars track exactly what the sense pins read,
so that would point to a keyboard problem.
>Hang on... What happens if you press a (printing) key
-- say 'A' and
>REPT. Do you get consistently correct punching? What
is printed? Always
>the same (incorrect) chaaracter? (if so, which, and
where is it on the
>cylinder). A few different characters (again, where
are they on the
>cylinder)?
Considerable improvement after working over the
carriage again. Many of the characters now print
correctly using the REPT workaround. Some examples
that don't:
Prints
Typed As
----- ------
Q S (consistently)
8 : (consistently)
9 ; (consistently)
X P,Z
E E occasionally C
W W occasionally G
A C
Haven't had time to analyze these yet in terms of
where they lie on the typewheel.
>Besides checking the clearence, it might be a good
idea
>to remove the keyboard and watch things while hitting
>a key. You might see something a little sluggish.
>You'll need to manually reset it after each
keystroke.
>It is a lot easier to see things when the machine
isn't
>jumping everytime you hit a key.
>Dwight
I'll try this again. I am sure that this is keyboard
related.
List of other things to fix:
dashpot - carriage always sticks at l/h side.
reader doesn't advance tape - presumably it should.
Regards,
Dave
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> The PSU is an H7109-00.
Mine says Model Number: H7109-C on it.
>>Most DEC machines have at least one power-OK line from the PSU.
>
>I want to figure out which that one is.
I think there is no such line. On the mainboard connector to the PSU, there
are Red (3), Black (4), Orange (1), and Blue (1) wires.
Red are all connected together, and all go to appx. 5 V when the system is on.
Black are all connected together and to ground and are always at 0 V.
Orange is one wire, and goes to appx. 12 V when the system is on.
Blue is one wire, and goes to appx. 12 V. when the system is on.
The red and black cross-connections are true on the mainboard and on the
PSU. They are not all adjacent on the connector, which makes not much sense
to me, but that's how it is. Red and Black on the mainboard connect to the
corresponding colors on the Disk power connector.
As for voltage: I really need a good DVM. Calibrated the 12V setting at
work against a good 4-digit fluke DVM, so I think my reading of 12.1V for
orange and -12.0 for blue is close. Did not have time to check at 5V, but
afterward measured 3 Ray-o-Vac Renewal D cells in series at 4.7 V, so I may
not be way far off. If so, my reading of 5.3 to 5.4 for the Red group is
worrisome. This reading is consistent even at the Disk power connector.
Anyone else have a good VOM, a working VLC, and 3 Renewal cells? Or just
the VOM and either of the other two?
>I have not figured out correlation between temperature and working status.
I know more about it, now. Turned it on cold, it ran for a while, then
failed, then started to try to boot again. Blew the hair dryer on it, it
went into hard fail almost immediately and did not try to boot. Blew a fan
on it, it went OK and actually ran far enough to give me a login prompt. In
both cases I was trying to aim at the part of the mainboard near the power
connector, but the system is so small I was probably affecting most of the
mainboard and possibly a lot of the PSU as well.
Near the power connector are two power-looking components (as in they have
big leads, and in one case a heat-sink attach point, whereas nearly
everything else is microscopic surface-mount stuff). One is a
power-transistor looking thing with a heat-sink attach point (but no
heat-sink) that has 3 pins and says
LT1086CT
9151
The right leg is connected to 5.3 V (Red-wires).
The center leg stays around 3.4 V, system running or failed.
The left leg stays around 2.15 V, running or hung (as far as I can tell).
The other is an 8-pin DIP that says
M9124
LM393N
QST
Are these two part of a crowbar circuit, or reset circuit, or some such?
Should I be able to see some clue about why the system hangs by looking at
their pins?
- Mark
I just took delivery of a PDP-11/23 with (amongst other things) 4 RL02
drivers on it . The system was in the hands of another collector in
florida and has not been powered up in quite a while.
I would like to make sure the drivers are cleaned and lubed before I
attempt to power them up... does anyone have any points to a print-set
and maintenance data for these drives? Any experiences people have had
bringing RL02s back to life would be greatly appreciated! Also, any
pointers/experiences re: potential cleaning issues of old RL02 packs
themselves would be helpful too...
regards,
David Spector
------------------------------------------------------------------------
-
David HM Spector spector(a)zeitgeist.com
software architecture - network/security consultation
technical due diligence - technology planning/analysis
Office:(631)261-5013 Cell: (631)431-5756
>From: "David Comley" <david_comley(a)yahoo.com>
>
>>Hi
>> You haven't made it clear about punching. Does it
>work
>>correctly when you use the punch?? If it does, it
>can't
>>be the keyboard, distributor or codebars. All of
>these must
>>work to have the punch work correctly. The punch is
>>mechanically connected to the code bars of the
>printer.
>
>When I punch single characters to tape, they punch
>incorrectly. When I hold REPT and punch to tape, the
>correct character is punched.
Hi
Ok, this is entirely different. I would have to agree that
it is more likely in the keyboard. Nothing much else would cause
this problem. Most all of the other moving parts would
respond close to the same for the repeat key ( still
might be something that is sticky though ).
Besides checking the clearence, it might be a good idea
to remove the keyboard and watch things while hitting
a key. You might see something a little sluggish.
You'll need to manually reset it after each keystroke.
It is a lot easier to see things when the machine isn't
jumping everytime you hit a key.
Dwight
>
>I had the keyboard apart last night. Cleaned the
>contact wires and the common terminals. Tonight I am
>planning to reset the contact wire clearances as the
>manual comments on contact bounce being an issue.
>
>Regards,
>
>Dave
>
>
>__________________________________________________
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>
Antonio said:
>I opened up my VLC and it has an H7109-C PSU in it.
Ok, good. Matches mine, so at least I know where to get another one of those.
>Can't you either borrow
>a known good one or at the very least pick up a VLC
>from ebay for less than $50?
Possibly, exploring that. But I'm reluctant to board-swap until/unless I
get reasonably strong evidence that it really is the PSU. Although in this
case, the failure is obviously not enough to fry anything, so I'm not so
likely to damage the known-good component by board-swapping.
This PSU is pretty clean and doesn't show much evidence of damage. Though
I'll bet a capacitor with bad ESR looks like a healthy capacitor.
---
Thanks for the reference, Frank! JT Computer may well end up $50 richer.
---
Tony said:
>_Sometimes_ the voltages are marked on the PSU PCB (particularly if it's
>a 3rd-party unit). But I guess you've looked there.
I did not unscrew the PCB from its mounting plate so I could see the back
side. But all the Red wires soldered down to little metal strain-relief
collars standing side by side, with resistance between them = 0. Likewise
for all the Black wires. Resistance Red/Black was about 5 Ohms, FWIW.
>What you are
>looking for is a +5V or ground signal that's _not_ directly connected to
>the appropriate PSU output (check this with an ohmmeter with the machine off)
I'm pretty sure it doesn't exist. See my earlier post.
>Buy a can of freezer spray. It's not _that_ expensive, and it'll do the
>job properly.
Plan A for the weekend involves a trip to the local elx. place. I'll try to
get freezer spray and replacements for all of the electrolytics near the
output wires on the PSU. Then I'll try to nerve myself for some soldering.
I'll keep the freezer spray away from the PSU.
----
Toth said:
>It certainly sounds like something is overheating. You might want to try
>using some cardboard to carefully direct the airflow from your hair dryer.
OK, will try it tonight.
>Do these systems have an internal fan? I haven't been inside one enough to
>remember, but if they do, is the one in your system running properly?
Two, side-by-side, mounted in the PSU housing. They suck air out of the
mainboard compartment into the PSU housing, and it then exhausts out the
far side of the case. They are not far from the connector and the
components I listed. Both of them turn when the switch goes on. (Thanks for
the suggestion, Emanuel!) Both had a *little* dirt around them, but I
cleaned that up (and both still turn). The SCSI cable partially obstructs
their apertures - I'll try to alleviate that.
>Linear Technology 1.5A adjustable voltage regulator, TO-220 package.
That's it.
... (!) "100% Thermal Shutdown Functional Test." !?!?!?
Maybe I'll give that part some stricter attention with the hair-dryer. Any
chance that thermal-shutdown function could be getting too sensitive on me?
Or that its thermal mounting has been messed up somehow? The mounting tab
looks like it could go to a heat-sink, but there's no heat-sink attached.
But there *is* a matching hole underneath in the mainboard!
How do I know if it goes into thermal shutdown?
>Low Power Low Offset Voltage Dual Comparator
>
>Datasheets can be found here:
> http://www.national.com/pf/LM/LM393.html
Ok, what's it doing there? Anyway, I'm going to try to probe its outputs
tonight and see whether they are in different states when the machine is
locked up.
As always, I'm indebted for all your help! More reports tomorrow.
- Mark
Does anyone know the trick to get the Mac IIci floppy drive out to gain
access to the battery?
I've got the hard drive out, and I took out the (1) screw in the
upper-left of the drive holder. Are there release clips to release the
drive holder? If so, where?
Thanks.
- Bob
