IBM 1620

Tothwolf tothwolf at
Fri Aug 28 20:31:16 CDT 2015

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.

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