Wicked hum in 5E3x2 build

[Josh_B]

I just built a 5E3x2 and it has a brutal loud hum that is unaffected by chopsticking, removing preamp tubes, etc.
The amp does work, somewhat, although the hum drowns out most of the guitar sound.
I have checked and rechecked my work, cleaned up lead dress and layout, measured voltages and resitances, resoldered every joint, resoldered the ground plate, and I STILL can't get the hum to change in any way.
I have consulter the Tube Amp debugging page, changed rectifiers, etc.
I almost think it's gotta be a transformer or something.

I have neatened things up quite a bit since this photo was taken - still no change in the hum.

[Gee]

From your picture, it looks like the heater wires running from the Pilot Light to the first power tube are too long and are routed too close to the next power tube. That could cause the hum.

I find the best way is to run the heater wires from the PT to the Pilot Light first, and from there to the first power tube in way that is as direct as possible.

[Satamax]

From your picture, it looks like the heater wires running from the Pilot Light to the first power tube are too long and are routed too close to the next power tube. That could cause the hum.

I find the best way is to run the heater wires from the PT to the Pilot Light first, and from there to the first power tube in way that is as direct as possible.

Yep, and you have that orange and red bundle parallel to the heater wires too, who said capacitive coupling? Well, if you want to rule out the heaters, temporaryly wire them as DC! Can't remember how to make 6.3/6.7 DC out of 6.3 ac, but someone will tell you.

[Josh_B]

Thanks, guys. I will check that out and rereout those heaters.
The orange wire is now grounded to a lug on the PT bolt, as I found out that it is an internal hum sheild for the PT.

[Bruce / Mission Amps]

Josh, fire up the amp and let it hum for a bit and then listen very carefully to the hum... now put it in standby and listen to see if the hum stops instantly or if it fades out over a couple seconds.
This is hard with cathode biased amps running high plate current because it drains the filter caps fast but try to listen for the hum to fade or die instantly.
If it fades then the noise is high voltage B+ power supply noise.. if it stops instantly, then it is 6.3vac filament supply noise.

As per the schematic, you do have the 6.3vac winding referenced to ground (through it's 6.3vac center tap or a 2 x 100 ohm virtual center tap)... or as I recommended, to the power tube's cathodes, right?

Another trouble shooting trick is to remove one green wire from the PT to the first place the 6.3vac is connected to the amp circuit.
This will kill all filament voltage to any part of the amp.
Then use a clip lead jumper wire to reconnect it.
Fire up the amp and let it hum for a bit and then undo the temp 6.3vac clip lead from the circuit.
Same as above... instant noise reduction means the filament supply is interacting with the audio amp.
Also, since you say the hum is as loud as the audio you are trying to amplify, this suggests to me me a possible miswire from the filament supply to the grid of one of the power tubes on the socket.
The miswire could be as simple as a solder blob that is touching both a grid and the filament lug... etc.... check lugs 7 (filament) and 6 (1k5 grid stopper resistor) for a possible short.

[spangler41]

One other thing to rule out is if the output transformer primaries (blue and brown wires) are reversed. If reversed, this will generate a very loud oscillation which some may consider a hum. I learned this the hard way on an earlier Weber kit build - I had overlooked that suggestion printed right on the schematic and paid a tech to find it for me.

My Weber 5E3X2 turned out good. I later built an external cap board using an AB series board, used 'totem pole' configuration with 2-220uf in series for main filter and 40uf for screens. It's in a tweed cab with a pair of Jensen Neo 12 4 Ohm wired in series.

[Wittgenstein]

I can't see from your picture, but does the PT have a center tap for the heaters and B+? If not, did you add a virtual center tap?