[Boatanchors] LK-500ZC Amplifier Help

[Rob Atkinson]

It sounds like the blown resistor is an in-rush current limiting
resistor.  The 2200 mfd cap probably has to do with a time delay.
This is just a guess based on what you have posted.  The resistor is
supposed to only be in use for a second at most.  When in-rush
resistors burn up it's because they stay in series with the primary AC
to the high voltage supply transformer.  A long tune up with the amp
will pull too much current through that resistor and it will fry.  The
relay isn't taking the resistor out of the circuit.  Something is
wrong with the time constant circuitry, i.e. that 2200 µF cap or
something else.  Look to see if the top of the cap is bulging out.  If
the board isn't complex you can shotgun everything out that's
associated with the relay coil and see what happens.  First replace
the 20 ohm resistor and fire up the amp and see what the relay does.
The resistor won't fry if the amp is unkeyed.

The other use of a resistor like that is as a glitch where it's in
series with the h.v. to the plate choke, but it doesn't sound like
that's what it's doing.

73

Rob
K5UJ