50's HP 711A power supply problem

[tonewood]

Bought a 1954 variable power supply for breadboarding my amps. It slowly drops voltage over time. From 300 VDC to 280 v in 1hr. Other than tubes and electrolytic capacitors in general, any ideas on what part or block might cause this. Schem attached.
Thanks!

[Structo]

Interesting.

I'm not up on that circuit but I would think it had something to do with a R/C time constant that works inverted but I don't see any huge caps.

Must be the actual circuit that does it.

I would like to know as well.

[tonewood]

Interesting.

I'm not up on that circuit but I would think it had something to do with a R/C time constant that works inverted but I don't see any huge caps.

Must be the actual circuit that does it.

I would like to know as well.

I will work on it this weekend & let you know what I find-

[tonewood]

Interesting.

I'm not up on that circuit but I would think it had something to do with a R/C time constant that works inverted but I don't see any huge caps.

Must be the actual circuit that does it.

I would like to know as well.

Structo-
I changed all the tubes, electrolytics and selenium rectifiers & the thing still drops voltage slowly. There are only 3 caps left in the amp (600v bumblebees) so I will change those out then quit. I'll let you know if that solves the problem.

[Cliff Schecht]

Sounds like a drifting resistor to me..