Humming V1 in Fender Pro Junior

[tomincognito]

Hi all,

I wonder if anyone might have experienced something similar to this...

I want to reduce the gain in the pre-amp of my Fender PJ, so I have tried a number of different tubes in the V1 but they ALL create a tremendous electrical buzz.

Please note the stock Sovtek 12AX7 does NOT hum or buzz in the V1 position, but I want to be able to adjust it and I thought I should be able to experiment without the buzz. I have tried a JAN GE 5751, EH 12AY7 but the sovtek is the only one that works properly. I wonder, is this related to tubes or related to the electrics?

Many thanks!

Tom

 

[Tesla88]

The schematic is quite simple and i don't see why changing V1 with a pin to pin compatible valve (same heater also) would lead to a buzzing amp , anyway can you better describe the buzzing sound?

Maybe is only due to bad pin contact or bad tubes . . .

http://support.fender.com/schematics/guitar_amplifiers/ProJuniorIII_schematic_Rev-F.pdf

 

[Tesla88]

Why start open topics with same issue?

http://www.diyaudio.com/forums/instruments-amps/228811-fender-pro-junior-tube-set-up.html

 

[tomincognito]

No reason other than the desire to attract people more knowledgeable than myself to contribute and ultimately expand my tragically under-informed mind.