Emulators of Classic Computers

From: Don Maslin <donm_at_cts.com>
Date: Thu Jan 22 23:29:03 2004

On Thu, 22 Jan 2004, William Donzelli wrote:

> > THe electronic design was abandoned for now. Basically I was to
> > (will...?) build a 4 x 4 switched cap memory which will be a nice
> > reality check on flops, tubes, etc.
>
> Please keep us informed.
>
> > Also, I chased down and read the exhaustive life-testing book the US Mil
> > sponsored (forget the title) in the early 60's re: tube reliability.
> > Though it applied specifically to subminis, it quantified what the
> > computing people knew: derate, derate, derate. They got easily 16,000
> > hours from selected devices.
>
> Subminis might also be a good choice, if you can find them. They "never"
> go bad. I don't think I have ever found a bad one. Their reliabilty was
> due to production in a clean room environment using very high purity
> materials. One interesting side effect was that submini tubes lost their
> sockets - the things were soldered right into the circuits, as the sockets
> became the most failure prone components.

IIRC, submini tubes were initially developed for use in proximity
fuses for anti-aircraft ammunition in WWII. I recall seeing some
during the early '40s that my Dad brought home from work - and
then took back. No need for sockets in a one use projectile!

                                                - don

> Most computer tubes were also built in the same clean room environment,
> and also tended to be very reliable. In the good old tube computer days,
> there would be a flurry of tube swapping for the first few months, maybe
> a year, of the computer's life, but then as the weakling runt tubes were
> purged, the machines became quite reliable.
>
> > The suspected more was easily possible, but
> > that was the extend of their testing. It was interesting that some
> > devices worked better/longer at slightly elevated Vff.
>
> The biggest advancement was the use of the IERC tube shields - the type
> that have ribbing inside to conduct the heat away. It took ten years, but
> the industry finally figured out the old style tube shields were a really
> dumb idea.
>
> > Also, if you look at general tube electronic environments throughout the
> > 50's, excepting the smartest stuff (Tek scopes etc) the power supplies
> > are total crap. Unregulated and unsequenced. That did a lot of harm. It
> > was fine for radios but not for "high speed" switching where margins
> > started to matter.
>
> The military radar things, specifically for IFF systems, had good power
> supplies. They were digital system, after all (specifially SIF encoders
> and decoders).
>
> William Donzelli
> aw288_at_osfn.org
>
Received on Thu Jan 22 2004 - 23:29:03 GMT