1972 fender twin reverb hum

[hlieboff59]

just got a vintage amp. A 1972 fender twin reverb in really great condition.
Only thing is reverb when put knob from 5-10 a hum appears and gets louder as you go to 10. I cleaned up all the pots with contact cleaner and even reverb input and output wires/connections to clean any dust on it. Still the hum appears. Is this normal for these amps or is it something I have to replace? Any help is greatly appreciated. Thanks for reading, Howard from New Jersey.

[majwild1]

I would get another 12at7 tube for v-4 and try that first, or there may be something loose on the inside does it change when you tilt it back on the legs?

[ZMAN]

I have found that a lot of hum from amps can be caused by power supplies. If you have the amp plugged into a power bar or some other type of cord, try plugging it directly into a properly grounded wall outlet. I had a loud hum suddenly appear in one of my amps. I tried everything to get rid of it and was pulling my hair out. I tried it with another amp in the same room, and got the same thing.
I thought it might be my pedal board, so I checked every pedal and cord, and still the hum.
After about 3 hours of wracking my brain,a thought hit me. My pedal board has a built in power supply so I thought it might be bad. I went to unplug it and found it plugged into a power bar that I use for my stereo.
My wife had done some cleaning and unplugged it from the wall to plug in the vacuum cleaner and plugged it into the bar. I put it back into the wall and the hum was totaly gone.
If that does not work, being an orginal 72 it is worth taking to a good tech. You can spend a lot of wasted time and money trying to trouble shoot the amp, when it could be something simple. Of course it could also be a 20 dollar tube, as suggested already.