IBM 1620

[Lyle Bickley]

On Fri, 28 Aug 2015 20:31:16 -0500 (CDT)
Tothwolf <tothwolf at concentric.net> 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
-- 
Lyle Bickley
Bickley Consulting West Inc.
http://bickleywest.com
"Black holes are where God is dividing by zero"