[R-390] R390A 2nd osc. hot R406, R407

[ngietz at mymts.net]

I wrote: Any thoughts on what might have cooked those two resistors?

Larry wrote: Are you using SS recs in your rx?  ...you should check C411 at 300 V, otherwise at 275V... if your line voltage is more than 115 VAC, you should also account for that.
    Yes, there are SS rectifiers, with no apparent voltage dropper installed.  I plan to deal with that later.  Line voltage is a consistent 117 VAC.  I did a leakage check up to 450V, no leakage at C411.

Charles wrote: Leaky capacitor(s) attached to S402 (C417 through 431E).  More likely one or more of the fixed capacitors (C417 through C428), but the variable trimmers are suspect, too.
    When I did the leakage test, I connected to the osc. B+ line with the circuit intact, then cycled the band switch.  If any of the above was leaking it should have showed up, no? 

Charles wrote: Replace the (resistors) that cause symptoms (i.e., troubleshoot the radio when it is not working properly, and otherwise leave it alone).  The exceptions are the well-known troublesome capacitors and a few resistors that run too hot by design.
    With the work involved to remove, clean up and replace the RF deck, I simply decided to take care of anything out of spec. on the assumption the designers picked most of those values for a reason.  Don’t want to do it again for a long time.  As far as those resistors that run too hot by design, does anyone have a list of the likely suspects?

Roger wrote: So once upon a time V401 went short and the resistors got burnt.  The tube got replaced.  The receiver worked OK and things were left.
     ...and, that’s pretty much the conclusion I have reached as well.
    Cheers,
    Nelson