So a very basic record player portable with an AM (only) tuner from the late 1950s. It’s a keep-sake from a friend who is almost 80 now wants it working again. He had bought it with his first pay packet at age 15 but it was in terrible shape. It even had errors in the design to do with the AGC that wasn’t working properly & a replacement cartridge with stylus for the turntable remains unobtainium. I have instead added a bluetooth mod as per Mr C’s approach after having followed someone else’s hopeless (i must say) approach!
The problem (the major trap) though was hum & i spent waaay too much time upon chasing down why.
I just rewired all the screen leads i/o again to try & stop an annoying background (50Hz here) background hum. And then as i lifted the entire chassis away from the workbench …. while is was powered, the hum disappeared!
The reason, my bench top is covered with a very old battered Anti-static mat! There are no Mains cables attached upon the underside of the work surface & there is no Earth connection to the mat as it ripped out years ago… but boy does it induce HUM…. into things.
It even solves the terrible noise issues using my scope on the shelf but not if its sitting on top the anti-static mat!
So should you ever run into such annoying Hum issues… try getting right of the benchtop mat that might be conductive!
Good catch. Tnx. for sharing your experience with us. 👍