Oscillation/squealing when volume on 10

jtm-45/dr504 · Post by **jtm-45/dr504** » Thu Feb 16, 2006 12:30 am

Okay, I got the amp up and running, biased the tubes, and plugged it in via my MASS (it's late). It sounds good, but when I dime the volume, on the treble channel I get a feedback-like squeal, and on the normal channel I get an almost tremolo-like oscillation sound.

What could this be? The only thing I've noticed from the kit instructions I didn't do is twist the wires that lead from pin 5 on the output tubes to the board, but they weren't when the other board was installed. Thoughts?

NY Chief · Post by **NY Chief** » Thu Feb 16, 2006 3:35 pm

Sounds like the shielding plate problem. Is the head in cab? Does the cab have the metal plate underneath the chassis? Mine did the same thing out of the cab. I installed the plate (alum flashing from the Depot is fine) in the head box and pur the chassis in. Problem gone.

jtm-45/dr504 · Post by **jtm-45/dr504** » Fri Feb 17, 2006 2:06 pm

Yeah, I checked the other posts about this problem while waiting for a reply, and they all indicated that having the chassis out of the headbox was the main cause of the problem. I'll throw it back in the headbox (wich does have the metal plate in it) and see if that solves things. Thanks!

Shredder · Post by **Shredder** » Sat Feb 18, 2006 6:07 pm

Also, if you fail to put VI's tube shield on it can cause squealing when chassis is out of the head box. Inasmuch, a bad tube in VI can also be the culprit since it only does it a full volume when amplified exponentially through the subsequent stages.

Steppan · Post by **Steppan** » Sun Feb 19, 2006 5:56 pm

When I was converting my 2204 to 1987 specs I forgot the input wires next to the OT wires entering in chassis hole. Just put them away from OT wires and is everything allright now.