IBM 1620

Mike Ross tmfdmike at
Thu Sep 3 19:46:49 CDT 2015

On Fri, Aug 28, 2015 at 5:08 PM, Lyle Bickley <lbickley at> wrote:
> On Thu, 27 Aug 2015 14:28:30 -0500
> Ben Sinclair <ben at> wrote:
>> The CHM has a bit of information, and links to three other 1620's that
>> they know about:
>> From what I've been reading, there may be only one operational 1620
>> right now, but the CHM is also trying to restore one.
> The IBM 1620 at the CHM is a running computer. There were two teams that worked on the 1620 at the CHM. The first Team got it running. Unfortunately, IBM used the wrong kind of solder on > the core memory and so the wires of the core memory literally "dissolved".

That sounds suspiciously like a problem Henk Stegeman told me he had
encountered with the core memory on a System/3; the problem there had
been a reaction between the core memory solder (or was it the actual
wires used to string the cores?) and the foam used to make a seal for
the air cooling through the core... either way, vital bits of the core
stack got dissolved by the foam over 40 years...


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