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The Pas is a recent purchase and was never run prior to the power supply replacement. Also replaced were the RCA board and power indicator lamp all frm tubes4hifi. The hum is in both channels. The hum reduces when at the mid position of attenuation. I was wondering if there was an issue with the pot itself or possibly the connected filter or resistor. All pots were cleaned prior to any work done. All grounds were reflowed, and solder flows were added around the gound on the line stage pc. I would appreciate your thoughts nd input.
Wayne
Glover
Follow Ups:
Hum problems are probably among the most difficult to solve. Are you saying that your hum increases and decreases with the volume control? If so, that kind of makes things easier because it suggests the problem is before the volume control, though it might be some kind of fault with the pot itself. Try shorting plugs on all the inputs and see what that does for the hum. You might also want to have a look at the wiring on the new I/O PCB, in particular the grounds. Did you retain or omit the 10-ohm resistors? The phono input ground should be separate from the other grounds on the I/O PCB. Is there any hum with the volume control all the way down?
Edits: 01/17/15
The hum decreases as the pot is turned up. The resistor was retained. The phono ground is separate. The hum is present with the pot being all the way down. I'll attempt shorting tomorrow and reply then. If you have any thoughts after this present reply I would welcome it.
Glover
The hum decreases as you turn the volume control up?
Yes at midway. Then near full attenuation the hum gets deeper in tone.
Glover
If the volume control is properly wired, and functioning properly, turning it down all the way grounds the input to the line stage, which is why we're more likely to hear about hum getting worse as the volume control is turned up, not down. If there is some kind of grounding problem in or around the volume pot, or some kind of ground loop (your new power supply's grounding, for instance), this might account for what you are hearing.Also, you mentioned that the volume pot was cleaned. I'd consider the possibility that whatever was done to "clean" the volume control might have caused or contributed to the problem.
So, at this point I am thinking some kind of wiring/grounding issue perhaps with the new power supply and/or a problem with the pot itself.
Edits: 08/25/15 08/25/15
I have to admit to never having heard of this kind of scenario. In this case, all I can suggest is to recheck the wiring to and from the volume pot - is it somehow wired-in backward somewhere in the related circuitry? Have you tried playing music through the PAS, and, if so, does the volume control work in the customary manner in controlling the volume level of the music? If you have not yet played music through it, I'd refrain from doing so until you get this figured out, as you don't want to risk full volume with the volume control turned all the way down.At some point, you might consider replacing the volume pot. I tried one of the less expensive replacement volume pots, but it did not work out well. I got a nice blue Alps replacement pot off of ebay. I suggest a 250K pot with loudness taps.
There may very well be more than one thing going on that is contributing to your hum. See if there is anything in the vicinity of the PAS that generates EMI and separate them.
Another thing I'd suggest is to replace the 10-ohm resistors on the I/O PCB with jumpers. I did this in mine and the hum was reduced. But, again, if you have other things going on, you'll have to ferret them out, one at a time.
IMO, this business of the hum decreasing as you turn it up needs to be resolved, first.
Edits: 08/25/15
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