loud hum in my new rocket build

[pancho510]

just built Trainwreck Rocket with 4 EL84s
im getting a very loud humming noise very very loud
the hum is constant doesn't change with any controls. I can play
my guitar thru it and all the controls seem to work fine and its loud like it should be. the hum never changes with or without guitar plug in or playing it.
I have tried to trouble shoot it .first disconnected R10 220k from the treble this had no change at all.then I tried to isolate output by disconnecting wires to c10 and c11 this did lower the hum but it was
still loud. So im thinking it has something to do with the 4 EL84s circuit.
I pulled each set of EL84s and it was slightly lower hum but both sounded
the same. now R27 I used 3 150 ohm zicon 10w resistors in parallel
instead of 50ohm 25w can this be an issue? also my layout sucks
B+1 and b+2 are 1 inch away from AC input would this cause a very
loud hum? any help would be greatly appreciated

[M Fowler]

Could be many things how about center tap on filament supply either the amp has a CT wire that goes to ground;

or two 100 ohm resistors one from each filament wire to ground. (artificial CT).

Filter cap not grounded. Solder blobs and/or wire leads touching chassis has been something I've done in the past.

Look the amp over carefully with a lighted magnifying glass, comes in very handy.

[RJ Guitars]

Pancho, take a look at this thread and let us know if it helps in any way - https://tubeamparchive.com/viewtopic.php?t=17505

Meanwhile - do you get the hum as soon as you power on the amp or does it come on after the tubes warm up?

[pancho510]

no hum at all until you turn the standby switch on.
if u turn power on with standby on no hum until the tubes warm up.

[RJ Guitars]

no hum at all until you turn the standby switch on.
if u turn power on with standby on no hum until the tubes warm up.

Ok great, that eliminates transformer coupling hum and lets you know that the hum wherever it starts at, is being amplified through the circuit.

Next I would start pulling tubes out beginning with V1. With no V1 in the circuit do you have any hum or any change in the level of the hum? If you still have hum then move on to V2, rinse and repeat...

[Richie]

pictures might help too. maybe someone could see a problem.

[pancho510]

v3 seems to be the problem
I get a very low hum with it out but its very loud hum with it in
and v1 and v2 out

[RJ Guitars]

Let me echo what Richie said... pictures are really great to help long distance trouble shooting.

Meanwhile, you've done some good work to get it down to the V3 phase inverter tube... although keep in mind there might be ways this could be fooling you. But as a next step take a long hard look at the circuit board and the tube socket wiring for V3, especially look at your ground wires. Verify that you have a ground wire from the turret where R11 meets C9. After that, verify that all your component values are correct... send us a photo or two and I'll expect you will have it cured fairly soon.

[pancho510]

alright I figured it out thanks to all the help here.
had the amp unplugged and I had a metal tool inside poking around
and I saw a spark on the ground side of one of the power caps.
oh sh.t I said not good. I thought I was getting this soldering thing
down they all looked good to me. I guess not. I started to re solder
grounds again and saw another spark from another cap oh sh.t
really dam I suck at this. well the hum is gone thx again for all the help.
still have some issues I'm sure its my great soldering technique.
I did get to play thru it for about 10 mins sounds good

[angelodp]

Be careful poking around with a metal tool in there. Even with the amp unplugged you might have very high voltages on the caps which would be very dangerous to you. Do you have a 'cap stick' to drain the caps? You should also check that the amp has no voltage on the caps before going inside.

[M Fowler]

Next time your out eating Chinese food pickup a new set of chop sticks. I have about 6 sets I use them all the time.

[RJ Guitars]

Ah good work. As you perfect your soldering, study up on how you can drain the filter caps. If you don't have bleeder resistors built in it's a simple thing to add them and you'll thank yourself for it. If you have a bad connection on the ground side of a cap I suppose it could hold a charge until it is solidly grounded. Using a shorting tool is always wise anytime you work inside the amp anyway.

I am going to take a guess that it was the filter cap that provides the power to V3 that needed the ground resoldered? Glade you found it and we are all a little wiser from your experience.

[pancho510]

yeah it was the cap on v3 and the bleeder resistors. so lesson learned
will start bleeding the caps before messing around better safe than sorry.
im a electrician by trade and been shocked too many times to count
but once I got shock trying to pull a fuse out of my JTM60 got hit
across my 2 fingers that was the worse shock I ever had luckly
it was only across my fingers.

[Zippy]

I had a metal tool inside poking around
and I saw a spark on the ground side of one of the power caps.
oh sh.t I said not good.

I started to re solder grounds again and saw another spark from another cap oh sh.t

still have some issues I'm sure its my great soldering technique.

will start bleeding the caps before messing around better safe than sorry.

im a electrician by trade and been shocked too many times to count

You have GOT to be kidding - bad soldering technique, a demonstrated disregard for electrical safety, and apparent lack of quality in your work.

I wish you good luck - you need it. Please consider changing your perspective toward electricity before it gets you.

I, too, was an electrician for many years - US Navy nuke.

Be safe out there.

[Richie]

Let me echo what Richie said... pictures are really great to help long distance trouble shooting.

Meanwhile, you've done some good work to get it down to the V3 phase inverter tube... although keep in mind there might be ways this could be fooling you. But as a next step take a long hard look at the circuit board and the tube socket wiring for V3, especially look at your ground wires. Verify that you have a ground wire from the turret where R11 meets C9. After that, verify that all your component values are correct... send us a photo or two and I'll expect you will have it cured fairly soon.

is it just me, or are the B+ supply flip flopped in those 2 drawing, or go to different places? the middle hookup is correct. hmm it didn't attach the pics from above post.. anyway, the pics posted of the board layouts.