[R-390] Oscillation Spurs

[Flowertime01 at wmconnect.com]

Patrick,

I have had some bad thoughts on this problem. You could have a tube in the 
RF deck with an oscillation at a few kilo hertz and just mixing with every 
thing. These are 50 year old radios and any thing is possible. Do not let 
this worry you and number of problems are still solvable. Just things get found 
in unexpected places.

Good that the calibration crystal is out of the mix.

Find some 47 Ohm 1 watt resistors. These plug in across the filament of the 
series tube strings so you can pull some tubes to break up the chain.

Start with the 3rd mixer. Pull the tube, bridge the filament, use a cap for 
isolation and inject 455Khz into the plate of the tube socket. Listen to 
what comes out of the audio. Pull the second mixer and repeat with a frequency 
that will mix with the VFO and see what you get. Work toward the front end 
until you get to the bad stage.

Roger </HTML>