Hum in RCA 45HY4

My RCA 45HY4 has developed a low fluttering type hum, even with the volume control all the way down. It had absolutely no hum after it was totally recapped. I suspected a bad tube as the culprit, so yesterday I substituted a complete set of four good tubes from another player that has the same tubes. Still, there was no difference.

What could cause this hum?

Help me out guys.

Caps? Even some new caps will fail prematurely. Ground issue? Dirty muting switch? Cold solder joint?

I suppose it could be any of those things. I'm going to open her up and take a close look.

Trying grounding the signal grid of the 12AX7 then the 35C5 tubes. Might be able to isolate the hum to one stage of the circuit this way.

I don't know how I fixed it, but it's fixed. I opened up the chassis and tapped on the top of the chassis with the rubber end of a screwdiver to see if any solder beads or other conductive debris might be lodged in the wrong place somewhere, then I subsituted an entire set of different tubes and there was no difference. I found one cap in the tone control circuit laying against the chassis, so I pulled that out a bit. When I re-installed the original tubes, the hum seemed to be gone. Now I can't hear the hum a foot away from the player. Now if you put your ear right up in the speaker, you can hear a very slight hum, but that's normal. I think it must have been the cap against the chassis causing the hum problem.

You had a B+ to chassis short, shoring it to cartridge.
That with coupling capactior from B- to chassis, you were also loading power supply.

By the way, read my post on your phono in ARF.
Bill Cahill

Bill Cahill wrote:You had a B+ to chassis short, shoring it to cartridge.
That with coupling capactior from B- to chassis, you were also loading power supply.

By the way, read my post on your phono in ARF.
Bill Cahill

Bill, I believe you are right.