Hi Gary,
It'd be interesting to see more details about your adapter board. There are a
couple of boards available that replace the system ROM with a JEDEC standard
256 or 512K EPROM that lets you update Y2K etc. and also add an option ROM in
the upper half; they just plug into an M100 but if one is willing to replace
the option ROM socket I suppose they could also be used as yours is. Also, a
number of people did the multi-image ROM trick with systems like the NEC etc.
that already used a standard socket instead of the Molex.
AFAIK there are no known issues replacing the M100 ROM with the 102 version;
IIRC the 102 mainly corrects a minor error in the 100's trig constants,
replaces the vertical bar with a Pi symbol and fixes an issue with the year-end
date (although it's still not quite correct).
Yes, corrosion or broken diodes and traces are fairly common keyboard problems,
from corrosive liquids being spilled or something heavy being placed on it
which flexes it over the little central support peg; leaking NiCd backup
batteries can also cause problems.
If by chance you have another 5 1/4 DD floppy drive or a 3 1/2 drive with the
appropriate adapters then I'd try replacing it to see if the problem is in the
drive or elsewhere; barring that, it never hurts to clean the head and clean
and lube the support rails. A PC that can use a 5 1/4 DD drive would also be
handy to test the drive.
Regarding the Club100 store, it is really a much smaller enterprise than it was
when it was Rick's baby, although the web site doesn't really reflect that.
Ken, the current 'manager', checks in here regularly and will no doubt be glad
to help if he can; unfortunately he has had some personal distractions so
please be patient.
Good luck, and welcome!
mike
----- Original Message -----
From: Gary Hammond
To: m100@lists.bitchin100.com
Sent: Saturday, March 19, 2016 7:38 PM
Subject: [M100] Greetings and some questions
Hi All,
I have recently joined the list and am glad to see there is still a fair bit
of stuff going on.
I am a collector of TRS-80 computers of which I have some Model 100s, 102’s
and a 200, DVI, TPDD and a TPDD2 amongst the other TRS-80 stuff. I have
repaired the non-working ones, and the ones which are not collector quality, I
have modified with a small option ROM adapter board I got made up to get them
into a more useable state. Some of the mods to date include:
a.. Replacing the non-standard molex 28 pin IC carrier with my adapter
board which allows either a 256K or 512K standard pin out eprom to be used. I
can use a jumper to switch between 2 ROM images in the 512K version. Not as
flash as a rex (ha pun intended!) but good enough to try out the option ROMs.
b.. Using the same ROM adapter to update model 100’s with the LH535618 ROM
with a model 102 ROM modified with the Y2K fix. Is there any known issues using
the 102 ROM in the 100? So far it seems ok but it has not been extensively
tested.
In repairing the faulty models, I have come across 2 instances where tracks
on the top side of the PCB where corroded. I one case it was an open circuit
trace that prevented the reset circuit working. In the other case, it was a
high impedence intermittent trace that caused the LCD –5v rail to fluctuate
resulting in random dimming of the LCD display. Is it normal to come across
these types of faults? Bear in mind that there was no other evidence of
corrosion and there was no sign of battery leakage.
On another M100, there were a number of physically broken diodes on the
keyboard PCB and a number of keys that needed desoldering, disassembling and
cleaning. Did manage to get the keyboard running in the end.
The DVI I have appears to have an issue with the 5.25” drive. It reads the
disk fine, but any attempts to write to the disk seems to make the disk
unreadable. Does anyone have any ideas or tips for fixing this?
And of course, the last question is while I get great satisfaction in
breathing life back into these, does anyone have some good working uses that
they put their portables to so as to earn their keep!?
Cheers,
Gary
P.s. Apologies for the long first post.
P.p.s. If the person who looks after the the old club100 shop lurks around
here, I tried to order some stuff but didn’t get a reply.
