I've been trying to troubleshoot a hum issue with my SL-65B/AT91 and I'm not sure I'm going about it the right way. Here's the symptoms:
- 60 Hz; sounds exactly like the hum of unplugged RCA cables
- Occurs even if the turntable is unplugged
- Quieted by connecting the factory green ground wire from the the turntable to the ground lug on the amplifier
- Gets very slightly quieter when touching the tonearm or frame of the RCA output under the chassis
With the carrier removed and the headshell contacts left open, the hum is very loud, which is what I'd expect from open contacts. With the carrier installed and R/L leads shorted to their respective grounds, the hum is gone. As I understand it, this indicates there's no loose connections from the carrier leads right through to the RCA inputs on the amplifier...right? Is the problem with the cartridge, or am I not testing enough variables (the impedance of the wiring, for example)?
Appreciate any help. Thanks!