Pavey VTM 60 preamp hum

[SoulFetish]

By the way you had answered my first question earlier, sorry I missed I it.
So g1 Asked if you had tried replacing or trying another tube in the PI.
Have you done that yet? (I would imagine you have).
So if you’ve already ruled out that it was a bad tube. Read the voltages at the cathodes, plates, And grids Of the PI tube.
what are the readings?

[Helmholtz]

No, it's not hum.

Amp hum relates to mains frequency, meaning it consists mainly of a 60Hz or 120Hz tone. Your noise doesn't have this.

What you have is a kind of crackling "static" noise.

[vintagekiki]

Before any intervention, check-clean all interconnect connectors and all tube sockets.
In the J6 (Return) put unsoldered male jack to disconnect the preamp from power amp.
If the noise does not stop, replace V4

If the noise stops, it is generated in the preamp. With the elimination method determine in which tubes is noise occurs. Remove one by one preamp tubes from V3 to V1 to determine where noise is generated.
When you find the tube which make noise, replace it with a new (not like new) .

If by replacing the tube (s) noise still exists, it is the thermal noise that is generated in some of the anode resistors that need to be replaced.

1)
https://www.youtube.com/watch?v=c2FwTZj8hCc
^{How To Fix Noisy Crackling Knobs/Scratchy Controls On Guitar Amp}

[g1]

Agree with VK, that kind of popping/crackling could be plate resistors. Or if those sockets are board mounted, you might have a bad solder connection at the socket.

[wormdirt]

Plate resistors have all been replaced
I'm going to reflow the PI socket, if that doesn't provide a fix, maybe a new socket is in order

[wormdirt]

Oh and the hum mentioned in the original post is not what I'm dealing with now

[glebert]

Maybe I missed something, but in the original post you said the noise goes away if you short the effects return jack to ground. That is essentially grounding the input to the PI tube. If that makes it go away it seems to me like the problem is before the PI.

[vintagekiki]

Does hum balance R9 (250 ohm) reduce hum.
If the hum balance does not respond, check R9 and the connection R9 with J1 (OT BD) and J2 (OT BD). At the ends of R9 (250 ohm) must be a heating voltage (6.3 VAC)

[wormdirt]

Maybe I missed something, but in the original post you said the noise goes away if you short the effects return jack to ground. That is essentially grounding the input to the PI tube. If that makes it go away it seems to me like the problem is before the PI.

Correct, but during the troubleshooting of that problem, I went ahead and reflowed the solder on most of the preamp and did some preventative maintenance by replacing the filter caps and coupling caps. After that was performed the sound I posted in the youtube video started

[vintagekiki]

Probably during preventive replacing the filter caps and coupling caps, cold soldering joint appeared somewhere.
With the elimination method (#18) determine which tube make sound posted in your video, and re solder all solder points.

https://learn.adafruit.com/adafruit-guide-excellent-soldering/common-problems
Common Soldering Problems

[wormdirt]

Probably during preventive replacing the filter caps and coupling caps, cold soldering joint appeared somewhere.
With the elimination method (#18) determine which tube make sound posted in your video, and re solder all solder points.

https://learn.adafruit.com/adafruit-guide-excellent-soldering/common-problems
Common Soldering Problems

Got it.
for posterity I'm getting
350v at the plates
55v at the grids
77v at the cathodes
This is for v4

[glebert]

I would try grounding the effects return input again just to see if that effects this noise.

[wormdirt]

I would try grounding the effects return input again just to see if that effects this noise.

It no longer effects the noise

[wormdirt]

ok I have re-flowed all joints that on every component I replaced as well as on the tube sockets. No help
i think this evening I'm going to replace the v4 socket since I have on on hand, maybe something exotic is at play here, such as an arc on the bottom of the socket.
Good news is that by trying every 12ax7 in my drawer I found that there is some difference in sound between different tubes, but this probably due to varying gain factors or quality

[vintagekiki]

Do you with the elimination method (# 18) determine which tube make sound posted in your video?