Hum only at volume

[C Moore]

I just put a new board in a 1969 Twin. I used all new components, new wire, and new pots. The tube sockets, choke, and three transformers are original. I also did not change the old, green, overhead heater wires. The power tubes are RCA and are pretty old. I do not know if they are original. They are fairly well matched for their age, 42MA 40MA 39MA and 34MA.
1. Is it a good idea to just go ahead and change/replace those old silver rectifier diodes?
2. On the reverb/tremolo channel there is a low hum until about 9:00 then it disappears. At about 2:30 it comes back real sudden and 10 times as loud. The only readings that raise a question with me is the 410 VDC on Pin 1 and 6 of V5. Should it be that high?
It happens whether there is a guitar plugged in or not. I have changed all pre-amp tubes, any coupling cap in the path of the volume knob, and played with lead dress a lot; none of this had any affect. Does the loud hum at high volume sound like a familiar problem to any of you guys?
Thank You

[Bob-I]

Sounds like a gronding issue to me, although it may be a tube as well.

These amps didn't have a really great gounding scheme. Soldering to the chassis is not really the easiest thing to do. I'd change that to some ground lugs in the correct locations. I'd also lose the brass plate behind the pots in favor of a buss like a T-wreck or Dumble.

[Bob-I]

Oh, and the 410 on the 12AX7 is way too high. That may be a grounding issue as well. Check the cathodes to make sure they're conducting properly.

[selloutrr]

I'd check the chassis grounds!
make sure the solder really flowed making a solid connection
then test continuity with the schematic.
It's possible to break the solid wire inside the sleeve.
If you have a set of know good tubes i'd try those as well.

[C Moore]

Thanks for the suggestions, I was starting to think the same thing. It does not seem to be a component problem at this point. I will check the grounds more thoroughly.
Thanks Again

[Structo]

Did you replace the Fender coupling caps? The blue molded Astrons?

Oh and which model circuit is it?

[C Moore]

Did you replace the Fender coupling caps? The blue molded Astrons?

Oh and which model circuit is it?

I made it to black face AB763 specs. Yeah I replaced those blue Ajax (or whatever brand they are) caps. All the components are new. The problem is the Opto-Isolator, Opto-Coupler, LFR, LDR, photo-cell, bug roach, I never did learn the proper name of that component. Anyway...the 400 B+ was not dropping at all across the 10 Meg resistor. I lifted the resistor leg that connects to the "Bug", and then I see the proper voltage across that 10 Meg resistor. A friend of mine has a new bug that he is going to give me. I am sure this will be the fix. If it is not, I will let you know.
Thanks Again

[Structo]

Ah, the old doodle bug.

Is your amp pretty? Can we see?

[C Moore]

Ah, the old doodle bug.

Is your amp pretty? Can we see?

I have really been struggling with the new camera my wife bought. That is to say, struggling with the camera software. Kodak Easy Share. IMO there is nothing easy about it. But yeah, OK, I will give it a try.
Regarding the rectifier diodes, do you guys just go ahead and change those when the amp is 40 years old?