[Amps] MLA-2500 Bandswitch Arc

[Kim Elmore]

As I've been working on my Dad's MLA-2500 (not the B model), I've 
noticed that at some point in time, there must have been an arc 
between the 10 m coil tap contact and the adjacent ground contact. 
For those of you familiar with the amp, this is on the front-most 
wafer. The contacts are otherwise perfectly intact: I see no other 
evidence of overheating and the solder looks fine save for evidence 
of the arc. I have no idea what the conditions were that caused the 
arc and my Dad has no recollection of it. Neither of us can even 
think of when the amp may have been used on 10 m.

My question is: what (if anything) should I do to clean up the 
carbon-like deposits left on the ceramic of the switch? Will alcohol 
and small tooth brush do the job? Acetone? Should I even bother?

Kim N5OP