Noisy reverb in Fender amp.

C/G · 1st November 2005, 03:21 PM

I have an old Fender Quad Reverb and when my reverb is engaged I get this annoying hiss. Sounds kind of like pffffffffffffffffffft. Anyway, I tried a new tube in the reverb driver slot and it is still there. The amp was recapped and "blackfaced" by an awesome tech, but unfortunately he does not live in my city anymore. Could it be a bad capacitor or something in the reverb circuit? It is bugging the crap out of me. Suggestions?

Jim Williams · 1st November 2005, 04:09 PM

Sounds like a bad preamp recovery tube. It's the one on the power transformer side of the reverb driver transformer. Pop in a new 12Ax7A or 7025.

Jim Williams
Audio Upgrades

C/G · 1st November 2005, 04:34 PM

Thanks Jim. If I am standing behind looking at the back of the amp, is it the second tube in from my right? The tube that is in that spot I am speaking of is a new tube as well, but the noise just started to happen. Jim, I still have to e-mail you the schematic for the gefell MV692's to look at.

Jim Williams · 1st November 2005, 05:13 PM

It's the one just to the right of that small reverb transformer. Pop out the first 12ax7a farthest to the right (the normal channel preamp tube) and try this one to check.

Jim Williams
Audio Upgrades

C/G · 2nd November 2005, 02:41 PM

O.k. I tried the second one in from the right (if I am behind the amp) and it seemed to tame down the hiss a bit. It is still there when I turn the reverb knob up. I thought the 1st tube in from the right was the channel one pre amp tube. I usually only go out of channel 2 with the verb/tremelo.

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1st November 2005, 03:21 PM	#1
C/G Lives for gear Join Date: Dec 2004 Location: Canada Posts: 2,796	Noisy reverb in Fender amp. I have an old Fender Quad Reverb and when my reverb is engaged I get this annoying hiss. Sounds kind of like pffffffffffffffffffft. Anyway, I tried a new tube in the reverb driver slot and it is still there. The amp was recapped and "blackfaced" by an awesome tech, but unfortunately he does not live in my city anymore. Could it be a bad capacitor or something in the reverb circuit? It is bugging the crap out of me. Suggestions? __________________ ------------------------------------------------------------------------ Colin G. http://www.myspace.com/generalsandmajors

1st November 2005, 04:34 PM	#3
C/G Lives for gear Join Date: Dec 2004 Location: Canada Posts: 2,796	Thanks Jim. If I am standing behind looking at the back of the amp, is it the second tube in from my right? The tube that is in that spot I am speaking of is a new tube as well, but the noise just started to happen. Jim, I still have to e-mail you the schematic for the gefell MV692's to look at. __________________ ------------------------------------------------------------------------ Colin G. http://www.myspace.com/generalsandmajors

2nd November 2005, 02:41 PM	#5
C/G Lives for gear Join Date: Dec 2004 Location: Canada Posts: 2,796	O.k. I tried the second one in from the right (if I am behind the amp) and it seemed to tame down the hiss a bit. It is still there when I turn the reverb knob up. I thought the 1st tube in from the right was the channel one pre amp tube. I usually only go out of channel 2 with the verb/tremelo. __________________ ------------------------------------------------------------------------ Colin G. http://www.myspace.com/generalsandmajors

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1st November 2005, 04:09 PM	#2
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 3,882	Sounds like a bad preamp recovery tube. It's the one on the power transformer side of the reverb driver transformer. Pop in a new 12Ax7A or 7025. Jim Williams Audio Upgrades

1st November 2005, 05:13 PM	#4
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 3,882	It's the one just to the right of that small reverb transformer. Pop out the first 12ax7a farthest to the right (the normal channel preamp tube) and try this one to check. Jim Williams Audio Upgrades