I have a combo set that I use frequently that has an issue with the audio. When I connect the TV and radio chassis electrical grounds together I get a buzz in my speaker. The sound is definitely higher than 60hz. I can use an audio isolation transformer to get rid of the problem, but I want to understand what's happening to cause the problem, and if it can be fixed without resorting to the isolation transformer.

Not sure what you are doing here but one ( usually TV ) may
have leakage most often at the antenna. Also use good
shielded wire or twisted pair & a real HEAVY ground wire.

73 Zeno:smoke:

Not sure what you are doing here ...

73 Zeno:smoke:

I'm connecting the TV chassis' audio output to the radio chassis' audio input, hence grounding them together.

I'm connecting the TV chassis' audio output to the radio chassis' audio input, hence grounding them together.

Odds are the TV has a hot chassis & you need a transformer to isolate it.
What kind of TV & radio are they ? Does the TV have jacks on it ?

73 Zeno:smoke:

It's not a hot chassis on the TV side. The set is an RCA Victor 730TV1.

Odds are one or both has capacitors or possibly resistors connected between power line and chassis if those parts have gone bad it could be the problem. One possible quick solution, if one chassis plugs into the other with a non-polarized plug, is to reverse the prong connections and see if that reduces the hum.