[vcf-midatlantic] November Workshop Update

jsalzman at gmail.com jsalzman at gmail.com
Mon Nov 11 09:15:26 EST 2019


It's been a while since I was at a VCF Workshop. This was the first time I
attended one in the Hackerspace. I don't know which working area I prefer
the most. The 9032-A building lets you S-P-R-A-W-L for sure. I found myself
uncomfortably encroaching in the Hackerspace building into space I didn't
feel I needed to take up. However, nobody seemed to mind, and I made sure
not to block paths and get in people's way. I did like the high top
workbenches and the fixed power strips with outlets every three inches. It
was very kind of the Hackerspace group to lend us the use of their
facilities (and the few tools I needed and did not have on hand). I hope
they soon develop a payment system for parts that they stock. I know
they're working on something to manage that process, but they do have quite
a selection of parts in stock. It would be a nice symbiotic relationship
between VCF and CDL when we are otherwise unable to source repair parts for
the items we fix by buying directly form CDL.

And speaking of fixing... I brought the following items to the workshop:


   - Kaypro 10 - garbage screen on the lower half of the display
   - Compaq Portable - former keyboard refoaming project which had issues
   after refoaming
   - (3) Coleco Adam systems - mainly for triage to determine what I have
   that works and doesn't
   - My MOBIDIC project stuff - In case I had free time to work on it
   - SupercardPro flux reader - To identify and archive unknown disks in my
   collection
   - Raspberry Pi 4 - because... Raspberry Pi 4!
   - All my 74XX and 74XXX chips - to count and sort if I got bored.


The first thing I did was start on the Kaypro. This was one of those
systems that worked fine when I put it away a year ago, but suddenly had
problems when I turned it on a few weeks ago. Thanks to the advice of Ian
and others, the display issue was the result of a bad 2128 RAM chip. Nevell
happened to have a replacement with him and it WORKED! Thanks again Nevell!
A Kaypro isn't a big thing for many, but it's my only dedicated CP/M
machine and I like to keep it running as long as I can.

BTW, the Kaypro 10 was kind enough to nominate me for the honorary "First
to Smoke" award, having unceremoniously given up it's RIFA cap before
lunch. Sorry about the air freshener, folks!

The next things I worked on were my Coleco Adam computers. These took most
of my time over the weekend (and most of my vehicle's cargo space). I have
one working system. A second system is completely DEAD, which I did not
attempt to fix due to issues and discoveries made while working on the
third one. The third one partially booted to the built-in Smartwriter
software, but locked up before it completed drawing the typewriter screen.
Subsequent resets of the system produced a consistently cascading set of
problems. First reset would only show a cyan screen. The next reset would
produce a blank screen. Each additional reset created a blank screen, but
at random, would introduce low volume sound tones.

After Internet research, and posts to the Coleco Adam Facebook group, I
discovered that operational issues like this could be the result of a bad
6801 in the system, or the surrounding operational logic for each one. Each
one meaning that the Adam actually has several support microprocessors in
them. I was unaware of this. Each support microprocessor is a 6801, which
is very similar in concept to the Texas Instruments TMS9000 series, where
the microprocessor has built-in mask ROM on board. So while several 6801
chips are in the system, they can't be swapped within the system to test
for a bad one, as they each have their own dedicated code. I'd have to swap
from a known good system, but even then, they are soldered to the board. It
would be a risk to try and remove a good one, just to test on another
system. They are not easily replaceable and there are not any known modern
alternatives for them (i.e. like the PLAnkton for the C64).

In all my research and struggle, I completely failed to test the other two
Adam printers I brought with me. If you weren't aware, the Coloco Adam
system's power supply is in the printer. Therefore, you need the printer
hooked up to the system to make it work. I just kept using the same working
printer to test the remaining systems in my collection and didn't bother
pulling out the other two printers I had to see if they worked

Since it was Sunday by now on this two-day Workshop, I decided to look at
my Compaq Portable. The keyboard on them are capacitive, not mechanical
switches. There are foam and mylar pads inside each key, and the foam
deteriorates over the years, rendering the keys inoperable.

About a year ago, at another Workshop event, I began to replace bad foam
pads in the keyboard. I had a pad kit that was long awaiting use, and I
finished the swap. However, the keyboard failed to work afterwards. I
didn't dwell on it too much back then due to other items I wanted to work
on, so I saved it for a future date and got back to it at this past
weekend's event. It was suggested by others that I carefully check each and
every pad to make sure it "snapped" under the all four clips on each key
top. I found a few that were not clipped in completely.

The symptoms of the keyboard were a 301 error upon boot and a "+" symbol on
the input field where it asks for system time. I'm thinking I have a stuck
key. This assumption is based on the fact that the mylar cap on the bottom
of the key foam on all keys is near flush with the body of the key as it
mounts against the circuit board. I'm guessing the aftermarket foam
replacements I got are too thick, and the mylar part is resting on, or too
close to, the circuit board contacts.

Maybe this Compaq Portable will show up at January's workshop...

Next, I brought out my SupercardPro. I have this conveniently mounted in an
old IBM external drive case, since it contains a working drive power
supply, room for my dual 3.5" and 5.25" half height drive, and the
SupercardPro board. The SupercardPro is a disk flux reader whose software
handles many disk formats. I had a bunch of unmarked disks from one of the
many disk lots I've acquired over the years and could not identify on other
systems. With a flux reader, I should be able to find patterns to help
identify a disk format.

Unfortunately, these disks were stored in less than stellar conditions and
have accumulated surface dirt and other unnaturally formed coatings. The
iron oxide layer was getting brittle and in some cases, had gotten scraped
away under the head of the floppy drive. So, I abandoned further attempts
to read any more disks and may consider them a loss. I think they may have
had CP/M or Minix data on them, if I remember correctly where I got them
from.

Finally, over the entire weekend, I spent about 10 minutes, tops, on my
MOBIDIC project, and that time was spend just showing its progress to
others and not any additional coding. I also did not get to any of the
remaining items I planned to work with as I ran out of time.

Thanks for the great weekend!

Jeff Salzman


More information about the vcf-midatlantic mailing list