Bad Capacitor symptom, can a Dr. diagnose?

Is it typical for the top of a Capacitor to have a bubble that you can push up and down?

Picture attached for reference, this is not THE Capacitor but this is the type. One of the big cylinder caps in my Bogner Rev 2. It is blue and I have no idea what it is called or what the values are.

Anyway on one of them you can literally push the top of it down and it moves in and out. It is very hard to explain so bare with me

Forgive me for the horrible artwork but you can see where the arrow is pointing to the red circle. It is not literally sticking out. I know I said bubble but it looks flat and normal but when you push in on it..it moves. One of them moves and the other does not.

Is that a sign of it is time for some new Capacitors?

Many modern caps use a plastic cover there on the cap that will warp due to the heat inside the amp. They aren't bad.

JerryP":25qa5s0d said:

Many modern caps use a plastic cover there on the cap that will warp due to the heat inside the amp. They aren't bad.

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Ok thanks, glad I asked. I have no issues with the amp. It sounds killer and everything is in order but it kind of scared me a little.

I figured I would ask before I bring it to my amp guy. Appreciate the help.

I noticed this on my Marshall 1959SLP the other day. F2 and F4 had bulging tops. I took it to my tech for another problem and asked him about that. He said it was nothing and not what he considers bulging. He said the paper tops puff out from the heat after a while. They looked easy enough to replace, so I wouldn't mind upgrading if it becomes necessary.