Sound Cutting Out on a Mark IV?

[LerxstFan]

Hi all,

I was playing at practice last night and my Mark IV B head started doing things I've never heard...I would be playing and touch nothing and then the volume would drop/ cut in and out, with a sound almost like a scratchy volume pot. Other times I would be playing and the amp would get louder all of a sudden without me touching anything on my guitar or the amp. I checked all the tubes and all seemed to be in order - I didn't see any dark tubes and the amp starts up and shuts down without hesitation. I checked my cables and pulled some effects out of my pedal board and still had the issue...any ideas? Thanks for the help - Jay

 

[TFC]

I had the same issue w/ my Mark IV. Turns out the issue was dirty input contacts in the FX loop. Cheap, fast & easy fix. See my old thread here:

http://forum.grailtone.com/viewtopic.php?f=3&t=43078&p=310881#p310881

HTH