[murphyv310]

Hi Ken.
To be fair Martin's approach will work but it's far from ideal. It can induce hum onto the waveform and distort readings but my main worry is it's potentially unsafe and not the best idea for a beginner.

I'd look out for a used isolation transformer 200 Watts would be fine for radios. I've a 1kw one which came from my old business, far too big IMHO. Re the tracer, they can prove useful but I think in your situation it won't help that much. Sometimes the loading and added capacitance can mask faults or even clear them which can be confusing. I think your radio has some form of instability that even taking meter readings will seem to effect a cure. Sometimes this kind of fault can be quite elusive to cure.