Humming V1 in Fender Pro Junior

tomincognito · 31st January 2013, 10:11 AM

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 · 1st February 2013, 06:45 AM

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...atic_Rev-F.pdf

Tesla88 · 1st February 2013, 06:48 AM

Why start open topics with same issue?

Fender Pro Junior Tube Set Up...

tomincognito · 1st February 2013, 07:10 AM

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

31st January 2013, 10:11 AM	#1
tomincognito diyAudio Member Join Date: Jan 2013	Humming V1 in Fender Pro Junior 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

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1st February 2013, 06:45 AM	#2
Tesla88 diyAudio Member Join Date: Dec 2011 Location: Italy	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...atic_Rev-F.pdf

1st February 2013, 06:48 AM	#3
Tesla88 diyAudio Member Join Date: Dec 2011 Location: Italy	Why start open topics with same issue? Fender Pro Junior Tube Set Up...

1st February 2013, 07:10 AM	#4
tomincognito diyAudio Member Join Date: Jan 2013	No reason other than the desire to attract people more knowledgeable than myself to contribute and ultimately expand my tragically under-informed mind.