presence stactic noise

[zackd]

This is probably a stupid question but,On a kt66 45/100 marshall amp i have problem i cant figure out. When I turn presence knob up it get a almost static sound that breaks up in a non musical way. When the presence is down no problem, I tried new tubes but it didnt fix the problem. It it just a dirty pot or bad pot? Thanks a bunch

[Flames1950]

If it's only doing this when you actually turn the control, it's perfectly normal -- there's some residual DC voltage across the presence control. But there shouldn't be any static when you leave the knob alone and play of course.

[zackd]

It is makes the noise after i turn it past 4 or 5. It is not while i am turning it,rather when i leave it there. When I play low notes it distorts in a crackly way. When i turn the presence down it go's aways and sounds normal.

[Structo]

What value presence cap and pot are you using?

What speaker tap are you coming off of?

[Omn]

Could be a dirty pot. If the pot has been placed in one spot over time (as you describe, on 4 or 5) there can be build up of dirt -from 4 or 5 and uppwards. If you are lucky you may clean it by turning the knob back and forth. Next steps would be some compressed air in to the opening on the side of the pot, with some extra knob-turns... Further cleaning would be a good electrical contact cleaner or just replacing the pot.

[Omn]

And PLEASE;

be careful working inside the amp. Even with it turned off, pulled wire from the wall, there can be HIGH voltage from the caps.

[Spodeeodee]

My 50 watt does this. Sounds like scratching a record on a turntable....kinda cool.

As Flames has pointed out, this is normal.

[zackd]

My 50 watt does this. Sounds like scratching a record on a turntable....kinda cool.

As Flames has pointed out, this is normal.

Yeah thats cool but that is not what the problem is. It is not making that kind of thing. I am still trying to figure it out.

What value presence cap and pot are you using?

What speaker tap are you coming off of?

My presence cap is a nos mustard.1uf and the pot is whatever marshall puts in there handwired head i cant tell by looking at it. I am going to try cleaning the pot but is a differnt kind problem i think. Thanks for a the help .