Ground hum driving me nuts! - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Bufo Bill · 28th Oct 2020, 3:12 pm

I believe GJ has it! I had to rewire the tone arm, the wire just was too far gone. The harness I bought had both the cartridge shields soldered into one at the signal out end, so that would explain it. Will have to see if I can get enough solder off the wires to separate them. Those little pins get stuck so easily, I still twitch when I think of soldering them! Probably will have to do it all again though.
Bill.

cathoderay57 · 28th Oct 2020, 10:41 pm

Hi Bill, I have experienced hum when a moving magnet cartridge is connected to my Quad22. The cause was pick-up of stray magnetic field into the pick-up adaptor plugged into the back of the Quad22. Although it is encased in an aluminium shield, that is ineffective against mag fields. The Quad22 was sitting almost touching the mains transformer end of the front Quad II. Although the Quad II mains transformer is shielded it was not effective enough. Moving the Quad 22 away from the Quad II quietened it down. Cheers, Jerry

Bufo Bill · 29th Oct 2020, 6:49 pm

Cheers Jerry, that's useful info to know.
Actually things seem much better now everything's put back into my wooden stand and the rear metal case replaced. It never quite sunk in before how much screening that "biscuit tin" offers!
Cheers from Bill.

28th Oct 2020, 3:12 pm	#21
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Ground hum driving me nuts! I believe GJ has it! I had to rewire the tone arm, the wire just was too far gone. The harness I bought had both the cartridge shields soldered into one at the signal out end, so that would explain it. Will have to see if I can get enough solder off the wires to separate them. Those little pins get stuck so easily, I still twitch when I think of soldering them! Probably will have to do it all again though. Bill.

28th Oct 2020, 10:41 pm	#22
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,384	Re: Ground hum driving me nuts! Hi Bill, I have experienced hum when a moving magnet cartridge is connected to my Quad22. The cause was pick-up of stray magnetic field into the pick-up adaptor plugged into the back of the Quad22. Although it is encased in an aluminium shield, that is ineffective against mag fields. The Quad22 was sitting almost touching the mains transformer end of the front Quad II. Although the Quad II mains transformer is shielded it was not effective enough. Moving the Quad 22 away from the Quad II quietened it down. Cheers, Jerry

29th Oct 2020, 6:49 pm	#23
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Ground hum driving me nuts! Cheers Jerry, that's useful info to know. Actually things seem much better now everything's put back into my wooden stand and the rear metal case replaced. It never quite sunk in before how much screening that "biscuit tin" offers! Cheers from Bill.