In article , "N_Cook"
wrote:

Smitty Two wrote in message
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In article , "N_Cook"
wrote:

Peavey Prowler amp from 1999. All the 1/4 inch sockets and one , only,
of
the valve bases , bad solder joints, reacted to the re-soldering
process as
though the tags were made of stainless steel or had a grease/oil film
over
them. What could have been the cause?

The causes of corrosion are many. I know you enjoy failure analysis as
an independent intellectual pursuit, but it isn't going to help you in
the repair. Salt air, cigarette smoke, corrosive flux used by an amateur
in a previous repair, they all have the same remedy: Remove and Replace
affected components.


I did notice an amount of black copper sulphide? corrossion over the brass
of the stand-off power switches - more like usual 30 years of black from air
bourne sulphurous gases.
This was failure to solder onto the pins themselves, the pcb pad solder
adherence seemed ok.
I still tend to a production problem as just one valve base Belkin and, not
at component making, as the jack sockets are Ream UK. Maybe contamination by
flood or fire or something like that at pre-production parts storage . If it
was greasy hands of a procuction operative I would not expect both surfaces
of each tag and all tags to be affected

I suppose one question is whether the bad soldering was original or
whether it developed over time. If original it could have been due to
corroded or poorly plated new parts as you suspect. Even well-made parts
corrode in storage (no flood required) so the mfr. may have used old
stock.

OTOH it's at least equally likely that poor original soldering was due
to operator incompetence such as insufficient heat or insufficient flux.

But of course (moving to option two) mechanical sockets are subject to
torture, and solder connections that start life healthy do crack over
time. Once cracked, the corrosion has a path to gain a foothold.