[R-390] Crystal Osc Deck Trimmer Failure

[Steve Hobensack]

I Just finished repairing my '63 Imperial. I had the 3/20 mhz trimmer cap fail, shorting out B+ to ground. The fault also
took out two 3900 ohm resistors within the deck. The 1/8 amp B+ fuse operated. The repair was difficult, mainly because I had to 
trace out the wire harness with an ohmmeter.  I made the repair by kludging in a 0.01 dc blocking cap in front of the bad 
trimmer. Replacing the trimmer was not an option due to the size of the wires and number of wires that would have to be moved.
The bad trimmer peaks up fine, however there is a bad place at a certain setting that will kill the oscillation. Why didn't
Collins use a blocking cap? After I put the receiver back together, I realized I could have put the blocking cap at the 
input to the band switch and blocked B+ from the entire trimmer network. If you have your xtal osc deck out for any
reason, it might pay to install a blocking cap as you would the "killer" cap in the IF deck.
 
Steve N8YE