Intermittant hum - Printable Version

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Intermittant hum - lasurveyor - 10-31-2018

Hi y'all, hope that you can give me some direction. I have a Philco 46-1203 radio/record player that I re-capped several years ago. It's played great for me, but recently a bad hum has begun intermittantly, both in the radio and record player. Playing with switches, the on/off on the turntable, the front on/off or the tone knob can get rid of it for some seconds then it's back. After the set warms up, about 20 minutes, the hum is gone and it plays fine after that. 

Could you give me some starting points to look? 
Thanks,
Alan

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RE: Intermittant hum - morzh - 11-01-2018

Start with cleaning tube sockets. See if all screws holding chassis together are tight.
See if any ground posts that are riveted have good GND connection, tap them with something plastic, see if it affects anything.
check your caps, especially the AC power filter (if present) for cold soldering spots.
And, as the last resort, change tubes one by one.

(all above applies if you are sure that it is gone after 20 minutes and not because some fluorescent lamp is there producing noise)

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RE: Intermittant hum - lasurveyor - 11-01-2018

Thanks for the direction, I appreciate your response. Yeah, my first focus was "is someone turning on a dimmer switch?" but after a while it's beautiful. Time to get her out of the case and start looking around.
Thanks,
Alan

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RE: Intermittant hum - Phlogiston - 11-01-2018

An "open" in either the volume or tone control can induce hum. In most cases this is caused by wear of the conductive strip and/or isolation of the wiper (contact). this is unfortunately rather common in late 30's Philco's and can be worsened by attempted cleaning of the control.

Yes, the volume can be affected.

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