Squeeling in channel 3

[Barry]

has anyone had squeeling in channel 3 if you have the main output up around 11:30 - 12:00 ?Im having this problem but its intermittent . My first guess is V6 preamp tube might be going .

 

[DeadAirD]

I just had the same problem. I was getting microphonic squeal on Channel 3 (except mine squealed no matter what volume) in Mark IV mode and a little bit on II C+ mode. So yesterday I made a trip down to the music store, bought a couple of 12AX7 Boogie brand tubes, and about thirty minutes ago switched out the preamp tube position V3... and that fixed it.

Below is a link to an older forum post I referred to. That member switched out V1 to fix his, but I guessed at V3 after referring to the diagram in the manual on page 62 and looking at which positions were what gain stages. I got lucky and guessed correctly.

http://forum.grailtone.com/viewtopic.php?f=33&t=37571

Hope this helps!

 

[rika_gd]

How are you conecting the amp? straight to the wall? using some upc?

 

[Barry]

Not using a power conditioner

 

[rika_gd]

cause ive experimented a bad functionality straight to the wall and with bad upc so, be aware, this amp is very sensitive
cheers

 

[eudaimonia02912]

My guess would be that it's one of the tubes. Unfortunately, given that it happens on channel 3, it could be any of them except v2.