Fender Twin amp noise

[blindboybenton]

Hi

Ive got a fender twin amp 94 that is making my hair fall out
I first saw the amp about 18 months ago. no sound i found R140 off V7A to be open. Replace it and away it went

Comes back a week ago. He was saying that its hums. I couldnt hear any hum but the tubes now tested on the DIVO one came up as faulty Replaced 6L6GC for electro harmonix and 2 of the pre amp tubes .bias at 60mv set the balance all good
But i seem to remember the amp being now no quieter than before. The noise is not a hum or an hiss, something in-between
Its not that loud i just think it shouldnt be there
Ive since tested the tubes again and the one JJ that failed the divo test, won't fail now

94-twin.pdf
If i remove V8 all quite
If i remove V7 the noise goes
this is what i see on Pin1 of V7
All the voltages around v7 are correct
Replaced V7 and V8 for new tubes
Ive replaced / swapped out R146 - R140
Ive checked the heaters and all Caps, No hum on HT Rails and ive piggybacks caps to confirm


Now i'm beginning to think i'm barking up the wrong tree and there is nothing wrong. For those who don't know. I have a basic knowledge of electronics and do this for fun and a part time job

Many thanks

Bassman

[Pedro Vecino]

Check visually resistors 108 and 109 (47 Ohms). These resistors are connected between the heaters and ground. The source of the noise could come from a lack of symmetry between the two. If that, sometimes a potentiometer of 100 to 500 Ohms with manual adjustment works better.
It's a posibility.