IBM 1620

[Tothwolf]

On Sun, 30 Aug 2015, Dave G4UGM wrote:
> On Sat, 29 Aug 2015, Tothwolf wrote:
>
>> IBM had special machines to position and thread them. 
>> http://ibm-1401.info/IBMCoreArraysIEEEMagnetics1969.pdf
>
> Thanks for posting that. Very interesting. Looking at it, the machines are
> extremely complex, but I am sure they could be reproduced, albeit at a
> probably prohibitive cost...
> .. I have marked for later reading...

Something else I forgot to mention, is that on page 8 in that pdf file, 
they mention initially using 60/40 tin-lead alloy solder for the enamel 
wire to the core plane terminals. On page 9, they describe switching to 
20/80 tin-lead so the solder would dissolve less copper from the enamel 
wire.

If repair of the core memory in CHM's IBM 1620 is ever attempted, I think 
either low-tin solder alloy with 1-2% added copper or possibly a more 
modern indium-lead solder alloy would probably be the best choice for the 
enamel wire to terminal connections since that would greatly reduce the 
likelihood of any future wire breakage.