Hi Netters

I've had an incident where two fine wires twisted and soldered together in a transformer assembly have gone open circuit. When the assembly is stripped down the twisted wires appear to have a residual solder coverage but insufficient to provide a proper solder joint. there is also a light powdery residue all over. It's as if the wires were soldered OK originally and some chemical reaction has stripped the majority of the solder away and left a corrosion product. The joint is within a sealed assembly, is covered locally in a protective tape and the transformer is impregnated before wiring. Does anyone have any history or knowledge of any reaction between transformer varnish and solder ? I appear to remember some problems with phenolic fumes attacking metals however I've never seen solder attacked in this way. Perhaps David Copperfield's been in town !!

Any feedback appreciated.

Bryan Kerr

Alenia Marconi Scotland