[ARC5] Dead BC-348-R

[David Stinson]

Resistor 57-5 is the Plate B+ resistor for
  the 1st IF.


There are two ways to burn-up this resistor.
Either there is a short somewhere between it
and the plate of 1st IF, or the resistor failed
by drifting lower, thus drawing higher and higher
current until it burns up, like the infamous
"Chernobyl Resistor" of Johnson Ranger fame.

The most likely suspect is indeed capacitor 11-9.
Is your tester passive or does it apply 200+ Volts
to check it for leakage?

Put your Ohm meter from the junction of 547-5, 11-9,
35-1 and coil 119, and the other lead to ground.
This should read a fully open circuit. If there is
leakage to ground, you need to find it.

If you don't find anything that would leak the B+
to ground, I would double-check the first IF tube
to see if it is weak.  If so, the resistor could
have drifted low, which would raise plate current to
the point the tube gives up.

If the tube is good and you don't find a short
ground, the next suspect would be capacitor 35-1
shorting and also raising the tube current, enough
to slowly roast the resistor.

If you find no leakage to ground as above, replace
resistor 57-5 and watch it for overheating.

GL OM ES 73 DE Dave AB5S

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