i have a curtis mathes solid state stereo with a AM/FM radio, a 4 speed turntable, and an 8 track player. the issue with it is through the main speakers the audio comes out normally for a split second when you change between a source but then goes mute. although the headphone jack works but you have to turn the audio up ALL the way to hear anything. also the volume control cracks loudly when adjusted.

I dont work on solid state gear, but that sounds like a capacitor somewhere that has gone leaky, upsetting bias voltages.

Since it crackles loudly its father back than the vol control.
Probably open coupling caps, the same one in both channels.
Probably electrolytics. How about a few chassis photos & model
number ? Maybe we can help.

73 Zeno:smoke:

You might want to try a little DeOxit D-5 on the selector and the pots. Capacitors may also be a problem at the age your Curtis-mathis set is.
A bad or corroded selector will put a damper on the sound too. Worth a try.