SV: [sdiy] Solder won't stick to old PCB

[David G. Dixon]

They used to sell this stuff for de-tarnishing silverware the easy way,
where you just dip the silver into this solution and it comes out perfectly
shiny.  I think it might have been called "Dip-It".  I think that
infomercial guy who just died (Billy something-or-other) was hawking
something similar on TV recently.  I don't know what this stuff is, but I'm
guessing it's some sort of reducing agent (sodium borohydride, perhaps?).
When I was a kid, I used it on bronze coins, and it worked perfectly.  I
think one could brush this stuff on oxidized copper traces/pads to the same
effect.

> Before now with badly corroded joints I've used a mildly abrasive
> paste like
> T Cut (For car paintwork) applied on a cotton bud, but clean well
> afterwards.