Here is my latest major acquisition as of the Sunday before last:
http://www.siconic.com/computers/Imlac
This is an Imlac PDS-1D, a later model of the Imlac PDS-1 circa 1972.
It's a 16-bit graphical workstation (pre-Alto!) I'm not sure how much
memory this has but it contains two coreplanes, so I'm figuring either 8K
or 16K. Unfortunately, it's been stored outside for about 7 years and has
suffered some minor corrosion on the PCB solder traces and some light
rusting on the ICs. I spent a few days cleaning it up and it looks like
it's going to make it.
This was a relatively easy retrieval. I started out from the San
Francisco bay area about 6am Saturday morning, making it to Long Beach
(southern California, LA area) by about 2:30pm, and got back home by 1am
Sunday (taking my time along the way). The actual distance was about 800
miles. I was able to fit the main unit in my trunk and the display in my
back seat. It normally would have come in a desk configuration, but since
it was stored outside, the formica and pressboard table top was warped and
unsalvageable, so I left it behind. I did get the legs, so I'll be able
to easily reconstruct the tabletop.
The cabinet of the computer was rusted around the outside. Not horribly
but it will need to be refinished. The inside of the card cage was spared
from any dirt and debris since it was closed pretty tightly. Some
corrosion on the logic modules from moisture was still evident. On the
other side of the rack, there were leaves stuffed up inside the core
memory board section. I imagine some varmint made his nest there for a
while.
I managed to clean up the core memory boards and the power supply section
so far. The core itself was fine, having been protected by a PCB board
cover. The leads on the ICs are a bit rusted, but I imagine they will
still be OK with some clean up. The solder traces showed some corrosion
(oxidation?) from moisture but seem to be OK after having traced out a few
with a meter.
The CRT is obviously going to need replacing. It looks like I may be able
to just remove the front glass panel and then chip off the intermediate
glass (plastic?) layer that is all cracked to reveal a clean tube on the
inside, but I don't know if this is just an optical illusion (and I don't
know if this would be safe :) The tube has a Fairchild sticker on it.
Apparently Fairchild made CRTs in the late 60s, early 70s. I wonder if I
can just find a replacement?
The nice thing about this one is that it came with the programmer's
console. And if you'll look at the picture showing the front card cage
with the logic modules, the long board in the lower right is a "Long
Vector Option", hand-wired by the guy I got it from. It's basically a
co-processor board for drawing the vectors on the display. It allowed the
system to handle more vectors than the basic configuration. Apparently,
if you had too much happening on the display the system would bog down
considerably or crash.
For comparison to the PDS-1, look here:
http://www.blinkenlights.com/classiccmp/imlac/
(This happens to be Doug Salot's excellent web page on the PDS-1, which I
now have in my collection...thanks, Doug! :)
The display for the PDS-1D is very different from the PDS-1. It's much
larger and has a detached keyboard. The computer itself is also very
different. The card rack uses different connectors, and the memory is on
the other side of the rack instead of plugged into the card cage along
with the rest of the logic modules, as with the PDS-1.
>From talking to the previous owner, I'd hoped I would be able to just
bring it home and fire it up after some TLC with a Variac, but that ain't
gonna happen. He never told me he'd stored it outside. Duh. But I think
with a bit of work it can be made to function in time for VCF 5.0, in
which I hope to include it in an exhibit of early networked video games.
One cool aspect of this machine is that it has a diode ROM board that
instructs the machine to boot off the serial port. The previous owner
wrote some code for his Cromemco that would upload operating software
into the Imlac. He also wrote an assembler on the Cromemco so that he
could assemble programs and then upload them to the Imlac. Pretty
cool.
This will be my main restoration project for the time being.
My first questions are:
1) What effect does moisture have on solder traces after such long
exposure to the elements? Do I need to be worried about cold solder
joints and things like that? The last time this thing was fired up was
6-7 years ago, according to the previous owner.
2) What is the chance that the power supply caps and transformers are
bad, again, being that it was exposed to the elements for so long? How
can I test the caps? I have schematics, so I imagine I could test the
transformers knowing the voltages.
3) How can I easily remove the rust from the leads of the ICs?
Thanks!
Sellam Ismail Vintage Computer Festival
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International Man of Intrigue and Danger
http://www.vintage.org
Received on Mon Apr 09 2001 - 20:10:31 BST