[R-390] Help! R-390 Meltdown

[DJED1 at aol.com]

Well I don't have detailed knowledge of the R-390 circuit, but usually a  
fried resistor is caused by a shorted bypass capacitor, or less likely, a  
shorted tube or pinched wire somewhere.  So- check the resistances at the  tube in 
question, and see if a measurement is off from what it should be.   I wouldn't 
fire the radio up again without resolving the problem.
Reminds me of my experience with a WWII Hammarlund Super Pro I  restored.  It 
was working well, but needed to be warmed up to have a  relatively stable 
oscillator.  So I let it warm up for a couple of hours  and then found it dead.  
A quick investigation determined that the B+ was  zero, and it turned out that 
a bypass cap had shorted right across the B+  line.  The remarkable thing is 
that the (BIG) power supply drove current  into that cap for two hours without 
any damage to the PS components,  although they got plenty hot.  I had 
recapped the receiver, but left a  few oil-filled caps because they checked out OK.  
This one had sprung a  leak, so it got recapped also.
These old Super-Pros were noted for shorted paper caps, and the destruction  
of the associated resistor.
Ed
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