[R-390] Oscillation Spurs

[Flowertime01 at wmconnect.com]

Patrick,

Keep working on it.

Not recommended, but you can loosen the band switch clamp and pull the band 
switch shaft out of the switch assembly. This may or may not give you some 
room to work on the resistor that needs changing.

You want to pull a tube to open the circuit so you can do a clean injection 
and thus isolate where the problem starts. Just putting the tube up on an 
extender does not help you break the chain and get a clean point to start 
injecting into.

Problem in the R390 is the series filament strings. Often when you pull a 
tube you loose at least one more in series and it is often the one you would 
like to be checking on. The 47 Ohm resistors in the power supply and audio 
deck work nice as filament substitutes. Back when these were always in stock 
because we were burning them out by letting the 6082s run until dead. You 
could get a couple out of supply when you pulled a 6082 or 26Z5's and no one 
would even ask why. 

Roger.</HTML>