"Asimov" wrote in
:

"Dave" bravely wrote to "All" (22 Jun 05 05:18:25)
--- on the heady topic of "Probably simple AM radio repair"
Dave,

The loopstick antenna can often be optimized by moving the pickup coil
along the length of the ferrite rod. However, I don't think this is
the real problem. There might be a break in the tuning capacitor or
its trimmer. Perhaps the rf xformer/mixer cans has an open coil.
Perhaps the local oscillator/mixer (transistor, IC) is stalling below
900KHz. This might be the supply bypassing electro for that circuit
being open, try tag soldering a good one across it. It should be
obvious where the problem lies by signal tracing with a scope or
demodulator probe. Was this an existing problem or a sudden event?

Thanks for the advice everyone! I should mention after tweaking the chokes
around the variable tuning cap, reception is acceptable to 750 kHz, but
there are a few stations below that I'd like to listen to. I bought the
radio with its current problem at a garage sale, it doesn't look like it's
ever been opened. I'll inspect the variable cap and chokes.

I do have a 5MHz function generator and a decent scope, is there some
advice on the net for testing receivers by injecting signals? I am mainly
a digital troubleshooting type and don't really know that much about tank
circuits and such.