IBM 1620

Lyle Bickley lbickley at
Fri Aug 28 23:36:44 CDT 2015

On Fri, 28 Aug 2015 20:31:16 -0500 (CDT)
Tothwolf <tothwolf at> wrote:

> On Fri, 28 Aug 2015, Chuck Guzis wrote:
> > On 08/28/2015 07:42 AM, Tothwolf wrote:
> >
> >> With all the different solder alloys I work with regularly, I have
> >> to ask...what type of solder caused that sort of damage? Was it
> >> the alloy itself, or did IBM use a flux which was too active and
> >> then failed to clean away all the residue? If they used a
> >> rosin-based flux, was it due to the specific activator used in the
> >> flux?
> >
> > That's actually a little puzzling.  1401 core frames have survived
> > well (got one in my desk drawer).  You'd expect that the same
> > process would be used for equipment that's pretty close to
> > contemporary.
> I think I've answered my own question today while looking at a
> datasheet for another type of solder. My guess is that the solder
> they used did not contain any copper, and the tin in the solder IBM
> used dissolved small amounts of the already very tiny copper wires,
> creating a weak point where the wires were soldered to the terminals.
> Lyle, was there any discussion of possibly laser welding replacement
> stubs of wire before the breaks that could then be re-soldered to the
> terminals? That would seem to be a viable repair option, although it
> would require special equipment.

I was not on the Team that did the memory analysis and the ultimate
"modern" replacement memory. However, when I joined the Team, I asked
similar questions and was told that the core memory was literally
"falling apart" and was not repairable. 

Lyle Bickley
Bickley Consulting West Inc.
"Black holes are where God is dividing by zero"

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