[R-390] R-390 B+ short

[wc4g@knology.net]

Hello to all and Happy New Year. Recently I found a B+ short in an R390/URR
on which I am conserving for a fellow. I found that the BFO ON/OFF switch
which receives B+ in all positions of the FUNCTION SWTICH had a 14ohm short
to ground. This switch is physically different than the ones in the "A"
model receiver. The B+ lead (red/wht/blu) is attached to a switch terminal
which is very close to the brass spacer which mounts the contact wafer to
the switch base. There was a carbon track caused by years of small arcing
when the BFO is switched ON. This is the second time I have had this
problem over the years. When I repaired the carbon track by cleaning and
using J.B. Weld as a filler, I used a hard plastic spacer instead of the
brass one. This cured the problem and hopefully prevented another carbon
track. This is something to think of when chasing down a B+ short.
Regards,
Don WC4G