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What might cause LOUD hum in a Conrad Johnson pv6

The PV6 today blared out a loud hum after it had been running fine for a couple of hours. I shut off all power to the amp, pre-amp, tuner etc. I noticed when I moved the preamp that one of the output cables was disconnected.
I don't know if it somehow disconnected and it caused a hum or became disconnected when I moved the pre-amp. In anycase, I later plugged the cables back in securely and used only a tuner STILL A HUM then a turntable and STILL A HUM.

I am looking for someone who might have an idea what is causing the hum. I opened the preamp No smell all tubes appear to be working. So I am puzzled.
randall
randallvar

Showing 1 response by almarg

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almarg
9,670 posts
 
Assuming you mean the hum is coming through the speakers, rather than directly from inside the preamp, and that you've somehow determined that the power amp is not responsible, I'd guess a filament-to-cathode short in a tube. Another possibility, more difficult to isolate, would be a failed capacitor, such as an electrolytic in the power supply section of the preamp.

Regards,
-- Al
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