Phonoland

When turned on, the Seeburg has good volume. After running for about fifteen minutes to a half hour, the volume noticeably decreases. This is true all the time. Trying to figure out where in the system this is likely to fall. i wondered if it is a tube failing after warm up, or same for a capacitor or resistor? Is it likely to be something in the AVC?

Needle cleaning is not the issue.

Appreciate any suggestions.
thanks!

And this is after the amplifier was rebuilt?

IMHO, this is a sign that the amp should be "rebuilt"--not just "recapped"-- I have found this to be a resistor changing value when warm-hot, most of the time. Ron Rich

Ron, that fits with my suspicion. I wondered if it might be a resistor failure. That is the direction I will take.
Thanks!

You can remove the outside rear cover, and try some "spray freeze"---
Ron Rich

reddfam wrote:When turned on, the Seeburg has good volume. After running for about fifteen minutes to a half hour, the volume noticeably decreases. This is true all the time. Trying to figure out where in the system this is likely to fall. i wondered if it is a tube failing after warm up, or same for a capacitor or resistor? Is it likely to be something in the AVC?

This is THE classic symptom of leaking capacitors. They cause this by becoming a form of resistor and leaking DC to chassis ground in some positions, and passing DC onto tube grids in others. The result is excessive conduction on the tubes which causes lowered B+ and distortion.

If not dealt with it will kill your tubes and possibly the power transformer. There is one capacitor in the AGC section which for some reason decouples to the B+ source instead of ground and this will cause lowered gain when it leaks. However, if it is leaking it is near certain that others are too.

Rebuild kits are well under $100 and if you feel capable with a solder iron, it will save both money and a lot of trouble/expense later-on.

Rob-N

Yepperz, those red-plating output tubes can kill volume and cook a few transformers in the bargain.
A real expensive mess to deal with later on.
Anybody with any "vintage" equipment should be warned to get it restored before use.