IBM 1620

Tothwolf tothwolf at
Sun Aug 30 20:01:42 CDT 2015

On Sun, 30 Aug 2015, ben wrote:
> On 8/30/2015 6:32 PM, Tothwolf wrote:
>> On page 5, they describe 0.0031" 40 AWG magnet wire being reduced to 
>> 0.002" after soldering with 60/40 tin-lead solder. That 0.0011" 
>> reduction is basically 1/3 of the diameter of the wire. This explains 
>> the failures of the enamel wires in CHM's IBM 1620.
>> Copper erosion from tin is something I'd never really given a lot of 
>> thought to, but it will certainly be something I keep in mind from now 
>> on.
> But is that the case? Would not heat induced failure be the real case 
> here as I suspect that a amp or two of current is flowing that now very 
> thin thread of wire? Digging though the doc's and a little calculation 
> clear this up.

My guess is that over time the thinned wires broke due to a combination of 
vibration and thermal fatigue. Vibration while transporting the system to 
CHM may well have been what ultimately caused them to break.

More information about the cctech mailing list