| whatgive |
| My vintage tube amp has a 500K pot to adjust the volume. It hums when I turn volume past 10'oclock. Any ideas what the problem maybe. It does not hum at all when volume control is at 9'oclock or less. |
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| fdegrove |
Hi,
| quote: | | It hums when I turn volume past 10'oclock. |
Most likely it hums all the time,you may just not hear it at lower volume settings.
The taper of the old 500K may well have a different attenution curve compared to what is commonly used nowadays.
The hum may be a ground loop or some injected hum from AC fed heaters.
It is also possible that a filtercap has dried up and lets the ripple through.
Cheers,;) |
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| whatgive |
| Ah, thanks for the tips - I will do a check up on those that you've mentioned. |
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| ashok |
Just a small warning. I once had a hum develop in my power amp when the volume control went past a point. It turned out to b eHF oscillation - I could see it on the scope. WHile you cannot hear the HF ( RF) its effects filter down ! Check to see if your power transistors are heating up suddenly . The RF is usually of very low amplitude.
Just a word of caution. In your case it might be just a hum loop ----- Hmmmm.
Cheers. |
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