Doubling capacity of first filter cap

[matt h]

I refuse to believe you have no heaters. There's a small chance some genius decided to DC rectify the whole heater string and did it poorly, an if your meter is set to measure AC voltage, you're not getting anything.

[V2]

If you have a 'stand-up' PT, the heater taps could enter the chassis through a different pass-through than the HT taps. Alternatively, you might have a separate transformer for the heaters.

Time for some photos of the amp!

[Meat&Beer]

Alternatively, you might have a separate transformer for the heaters.

Time for some photos of the amp!

That's also what I was thinking. Are the green wires coming off the PT cut off at the entrance into the chassis? Or, are they not in use/connected to anything? The heater tap may have gone south and a filament transformer added at some point. Hard saying not knowing, if you can, please post pictures.

If you put one probe on pin 4/5 and the other probe on 9 of one of the 12AX7 preamp tube sockets with your meter set to VAC, what do you get? Again, it should be roughly 6.3.

These are where your filaments/heaters connect, there should be a twisted pair of wires that go to each tube socket in this fashion. If your amp works, you have heater voltage, coming from somewhere...

[statorvane]

Since the amplifier appears to have limited space for chokes, humdingers, etc., wouldn't the simplest approach be to try elevating the heaters? I've built several SE amplifiers and hum is not a problem - no worse that my PP amplifiers.

If you can post some gut shots and schematic, that would enable people here to help chase down the problem, or resign it to physics.

[GERPUD]

After having sleep, with my eyes opened, I realised that my meter was on DC. So, yes, I get 6.3VAC between the two green...
Sorry guys...

For the schematic, I was not able to find it. Too recent and tee limited quantity I guess. Also, since I can't look to the back of the PCB. I would have to take apart every little screw of the amp to get there. That makes every thing harder...

I've put pictures.
I would have place next to the OT for a choke, but I'm not able to see how to connect it for whole filtration amp. It could easily replace the first resistor, but the OT wouldn't have a better filtration.

Now that I HAVE heaters!, I could try Matt suggestion, but I would need to understand why this "hum balance pot" would decrease this hum when "balancing the legs of the faux-center tap".

How "elevating heaters" does help with the hum?

Thanks a lot!

[GERPUD]

Can I put the tap of the OT after the first resistor (instead of before)?
This way it could be easier to get the whole amp filtered.

[GERPUD]

Here's a part of the power supply schematic I did. I'm not good at drawing, better at music.

From other schematic I saw, they have a CRC or CLC before to OT supply. I don't have that. I guess I don't have the choice to take everything off to get to the back of the pcb to be able to add filtering before the OT.

Any solutions?