Hi all, new here.

[Revor]

So I've just finished building a 5E3. What a fantastic sounding AMP!!

But... And there's always one.

Turn this map on and it's quiet as a mouse, as time passes it get's a hum, pretty significant really, the hum diminishes when the volume it turned to 11/12. All this is with no instrument.

I've double checked and reflowed everything, almost wore out a chopstick too, heater wire are twisted tight and laid along the chassis Marshal style. The PT have two center taps R/Y and G/Y (Classictone) both are grounded with the main wall ground and the ground on the output side of the amp to a lug on the PT mounting screw. The input side grounds, ground on a buss that terminates at the normal #1 input jack, all of the other input and output jacks are isolated from the chassis. The OT output ground is grounded to the chassis.

Any easy thoughts? I've been searching and searching for a soulution.

Thanks

[Jazz P Bass]

Have you tried any replacement tubes?
The hum may be a tube going gonzo.
Also, I would suggest that you monitor the B+ voltage.
Look for anything abnormal when the hum kicks in.
Like a change in Vdc or an increase in Vac (ripple)

[Revor]

No new tubes yet.
I have a spare set for my Bassman, 6L6's and 7025's that could work for testing I'm thinking, that leaves the rectifier.
Plate voltage to the 6V6's right? Pin 3 (forgive me while my dad taught me a lot about tube amps but it's been a while) the voltage from the PT.
Nothing visually is happening, like tubes looking hotter than before. the sound of the instrument is also the same if i plug it in, like no early breakup.

[Revor]

Well now we're in the right forum I 'spect.
This would appear to be good troubleshooting information as well.
Taking advise from Jazz P Bass I measured my plate voltages at pin 3 of the power tubes. As my hum grew louder the plate voltage got lower starting high at about 415 VDC and settling at about 392VDC, what was more interesting is that the AC voltage at the same pin was growing, going from a start of about 6 VAC to 16VAC
as the hum grew louder. So more ripple? 120hz hum? anyway i also noticed while poking around with meter leads and then a chopstick that the wires coming to the 12ay7 from the input side of that (V1) tube were very microphonic. I figured the tube must be getting something back from V2 (?) so I stuck a spare 12ax7 in V2 and the hum was cut by a tenfold (?!?!?)
Another thing I noticed was that the amp became much more sensitive to the meter leads when the hum was louder, popping and cracking when the lead touched the pin, it's a high end fluke DMM and it never pisses off solid state instruments or equipment.
What I noticed after the new 12ax7 is that the plate voltage started out lower 368 VDC and stayed there, also the VAC stayed constant at 6 VAC at the plate.
Having more spares I replaced V1 with no difference and the power tubes with some spare 6l6's (now I know all about "sweet" 6V6's) again with no other difference other than the tone of the amp.
It still has a hum (tolerable) and the tone and volume controls react as I would expect that is getting a bit noisier as they are cranked but only slightly.
Anyway thanks for the tips Jazz. I'm off to continue the pursuit of my dead silent 5E3.