Vox AD120VTX....no output

[acorkos]

when i turn the amp on, i can hear what i think is normal output hum, which gets louder and softer as i flip the power select switch...but no guitar signal. effects send jacks into another amp yields normal sound...guitar cord into effects return jacks makes no sound. nothing from the headphone or line out jacks, either. the hum tells me the power amp is generally ok, and what i have is a broken signal path somewhere around the master volume pot.

http://www.valvetronix.net/docs/AD12...l_Complete.pdf

anyone encounter this problem before? i am dreading disassembling the front panel to get into the master volume pot. thanks for your help...

[acorkos]

hello...?

[Danlampton]

I would trace the signal from the return jack forward. You will eventually find a component where the signal goes in but doesn't come out.

Good luck.

[J M Fahey]

Yesterday I repaired a friend's VT100 , not the same but a close brother, with exact same symptoms: practically mute, just some hiss which responds to the master volume and nothing else, *very* faint (less than mosquito buzz level) guitar sound in the background, with effects and all.

I'm visiting São Paulo's Brazil NAAMM type ExpoMusic2011 and he had to play there demoing some guitars.

Now get this: *ALL* of São Paulo is 110 V , so obviously everybody uses 110V amps (duh !)
*All* of ExpoMusic is 220V!!!! ...... and there is not a f*ck*ng poster, placard or even stamp sized sticking label stating so.
They should have a blazing orange fluo poster, with 2 foot high letters on every access door, stating "you are entering 220V country here" or someting like that.

Their explanation?
"The Stand owners should know, since their lighting, etc. is 220V"
Well, I'm sure stand building contractors knew, but most stand owners just order them and are more worried about the knockout girls they hire to lure customers into their commercial traps.

My friend was lucky, on inspection at his home (after his blood pressure blew through the roof), the amp just had the 12AX7 heater fuse blown.
I could have repaired the Power Amp or PSU if necessary (It uses an STK something and normal through hole parts) but if anything happened to the preamp/digital module, the amp would be junk by now (well, maybe it could be used as a 2x12" extension cabinet), it's just a proprietary CPU of the "repair by full replacement" type.
Well, I might have built a REAL AC30 there, if necessary.

So, in a nutshell, check that your tube works, it's not just a preamp as in a Valvestate but a symbiotic part of the Power Amp.
Good luck.
Oh well.