Latest Acquisition: Imlac PDS-1D

From: Tom Uban <uban_at_ubanproductions.com>
Date: Tue Apr 10 15:02:53 2001

Sellam,

Nice! I haven't seen this particular model before, but it has many
similarities with the PDS-1.

>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?

All of my Imlac displays have some amount of this disease, but not nearly
as bad as the one in your picture. I am planning on trying a test on one
of mine if I cannot find a replacement tube. The test constists of building
an enclosure with a pan in the bottom in which I can soak the face of the
tube in acetone in order to disolve the resin which is between the face of
the actual tube and the plastic protection layer. If the two can be
separated in this way, then the plastic can be re-attached to the tube
with a new layer of resin. This design is similar to the process used to
hold camera lenses together as they are often made up of multiple layers
of glass. I have a friend who repairs antique cameras and he suggested this
approach. As someone else noted, it would not be safe to operate the tube
with out the protective layer, but I hope that with careful handling, it
can be repaired back to new condition.

>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.

The console in your picture is also different than that of the PDS-1. You
have a wood enclosure and mine has what I think is a fibreglass enclosure.
More importantly you have a knob and mine has some discrete switches.

>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.

The keyboard on my PDS-1 is detached, but is molded/styled to match the
display enclosure. Interesting on the memory. Of the different models
I have seen, the memory does seem to move around a lot from design to
design.

>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.

It would be great if you get the machine up and running for VCF 5.0! I
have been considering bringing my this year as well, so if we both do,
perhaps we can "network" them...

>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.

I think this was normal for most of these (to load from the serial port).
I did see a unit which had an Iomega (RK05 like) removable hard drive with
it at one time. Sadly, the drive was discarded over the years.

>This will be my main restoration project for the time being.

Do you have the prints that you need. I have prints for all of my machines,
but they may be different enough that they would not help you. Let me know
if I can be of any assistance.

Your pictures have inspired me to put up a better set of images on my site.
I will try and do that tomorrow...

--tom
Received on Tue Apr 10 2001 - 15:02:53 BST