vintage computers in active use
elson at pico-systems.com
Fri May 27 11:20:57 CDT 2016
On 05/26/2016 10:40 PM, William Donzelli wrote:
>> Another CHM volunteer (from the PDP-1 Restoration Project) and I
>> pushed for an IBM 360/30 Restoration Project, and the ability to build
>> replacements for failed SLT modules was part of our plan.
> I am still trying to figure in which universe are SLT modules so rare
> that one needs to fabricate replacements.
OK, where can you buy some? They haven't been made since
about 1970. IBM sent out a letter to all 360 users who had
machines under contract, giving a date when they would no
longer guarantee that any particular machine could be
repaired, due to lack of spare modules, and a second (later)
date when they would drop all contracts and no longer make
ANY parts available, due to the need to keep the National
Airspace System running.
The IBM 9020 system was composed of slightly modified 360/50
and 360/65 processors, and attempts to replace them with
more modern technology had several notable failures. These
systems were in use until ** 1989 **!
They were finally replaced with IBM 3083 processors.
I suppose somebody may have a warehouse full of old SLT
cards, but I've certainly never heard of it.
SLT modules were NOT terribly reliable, as compared to MST
or newer technologies. Remember, SLT is DISCRETE
transistors and diodes on ceramic hybrid substrates. At
least in my experience, mid-size 360's would need a card
replaced every few months. I have no idea what the failure
rate would be in cold storage rather than in power-on 24/7,
which is what they did at Wash U. (ISTR that maybe Rolla
shut their 360/50 down every night. I don't know if that is
worse due to thermal cycling or better due to less power-on
But, I'll bet that oxygen and moisture will continue to take
their toll at a slower rate. Remember, all this gear is now
about 50 years old!
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