Motorola 7 inch tabletop

[decojoe67]

I had a bad buzzing in the audio on mine and had to clean and put 'liquid wire" on all the chassis tube socket rivets - the advice from my repairman. It worked!

[timmy]

Is it possible for a component such as a ceramic disc that goes from a given circuit to the chassis ground, which is one side of AC along with DC negative to go bad or short to let AC into the circuit. This set when it's turned off the speed of the hum quickly slows to a stop and the image as well shows it as a kind of ticking. But when it's at full 60hz you don't see it but hear it.

[dieseljeep]

Originally Posted by timmy

Is it possible for a component such as a ceramic disc that goes from a given circuit to the chassis ground, which is one side of AC along with DC negative to go bad or short to let AC into the circuit. This set when it's turned off the speed of the hum quickly slows to a stop and the image as well shows it as a kind of ticking. But when it's at full 60hz you don't see it but hear it.

The chassis on that set isn't a true return to B-. The chassis is somewhat isolated from the B- with a resistor and cap network.
Maybe a component is returning to chassis ground instead to B-. It's easily done by even seasoned restorers.