Peavey Studio Pro 112 amp pops loudly when switched off

[musogreg]

I have a little Peavey Studio Pro 112 Transtube amp that I use as my work bench amp for testing purposes. There is no warm up time so it suits my use quite well. It switches on with a just audible pop which gets louder as the volume control is adjusted upwards. When it is switched off it makes a very loud pop and the position of the volume control has no effect upon the level - it's loud and it seems to be getting louder!
For those with more knowledge about the inner workings of amps than I, is this a simple fix? Is it a cap that has died or something similar?

[reTrEaD]

Jul 30, 2018 20:57:28 GMT -5 musogreg said:

is this a simple fix? Is it a cap that has died or something similar?

I would *guess* that it's a power supply capacitor that's failing. But without a schematic, we're really just shooting from the hip. I have a good source for tube amp schematics (Schematic Heaven) but not for solid state amps.

What I'm guessing is happening is, this amp has a bipolar power supply. A positive supply and a negative supply. When the power is switched off, the side with the failing cap could be dropping to zero in a great big hurry.

Get your hands on a schematic and we can design a test procedure.

[musogreg]

Thanks for the advise

I have the owners manual but it only has a block diagram so I have emailed Peavey customer service to see if they can help

[thetragichero]

maybe off topic, but does anyone know what exactly the "transtube technology" is?
fets?
i did a little googling and ammo i found was either marketing material or people arguing on forums lol

[musogreg]

res.cloudinary.com/musogreg/image/upload/v1533084033/x0sqshurcuwhieqtv34v.pdf

Peavey got back to me overnight with the schematic (above) and the message that "This is referred to as an on/off transient pop. The pop could be caused by bad filter caps or bad DVL caps."

In searching the interwebz I did turn up another schematic (same one, but not as clear) and a YouTube of a guy who modded his amp:

res.cloudinary.com/musogreg/image/upload/v1533084210/gflwy3vjfcs7ycpslkhx.pdf

I haven't popped the amp open yet, but it is clear from the videos I watched that there are no tubes involved in Transtube technology

[reTrEaD]

I can't seem to follow that schematic, musogreg

They show the primary of the power transformer but the secondary and rectifiers are no where to be found. I wonder if they're talking about C85 and C86 when they refer to the "DVL" caps? Maybe it's just me but it looks like CR19, 24, an 45 are turned the wrong way round. I reckon I'd look at C63 and C76 first.