William Sommerwerck wrote in message
...
Complex problem, which I don't fully understand. But I'll respond
anyway...

Why isn't a reducing agent -- such as TarnX -- sufficient to remove the
sulphides? And once removed, wouldn't the sliders return to their original
state, with or without a bit of lubricant?

You needn't reply. I'm just asking questions to provoke thought.



Normally the gaps between the dual-in-line pins 2x13 here would only have
0.2mm or so spacing to maintain electrical isolation and unobstruced slide
action but these ones have large gaps and consequently have more requirement
of lubrication I would have thought.
The stop/go resistance to movement is much more than normal "wave-band
change" multiway multipole slide switches