[R-390] R-392 fixes itself

[Robert Nickels]

A while back I'd asked for suggestions on what might be ailing my R-392
which had very low audio.  I appreciate the hints but it turned out to be a
miracle cure ;-)

I followed the troubleshooting procedure outlined in the manual (one of the
best I've seen, btw).  I found that it is possible to run the upper deck out
of the chassis with care and one BNC extender but due to the presence of MFP
making it hard to probe the socket pins (not to mention it's crowded under
there!) I used the tip suggested in the manual and just stuck the end of a
short piece of small insulated wire into the tube socket pin I wanted to
measure and then plugged the tube back in.  A good "field expedient" if you
ask me.

Anyhow, I found good audio at the diode load but almost nothing on the grid
of the first audio tube.  I suspected a coupling capacitor but in this
Stromberg Carlson-built unit they are all Sprague Vitamin Qs and those never
fail, in my experience.  After probing around a bit - the speaker audio came
back loud and clear.  My best guess is that an ohmic connection had "grown"
thru the MFP at a point where the resistor on the grid made physical contact
(or very near) a grounded standoff.   This "fix" seems to be permanent,
although it's never as satisfying as when you find a bad part that you can
at least toss in the trashcan afterwards!

Just wanted to share a bit about the R-392 which remains another great
example of the 390 legacy.  One more thing - it only takes a few seconds to
remove the deck - just don't lose the oldham coupler on the bandwidth
control!

73 Bob W9RAN
PS:  Since I run this rx in a 24 volt vehicle, I'd like to find the solid
state audio module plug-in if anyone has one, tnx.