Musicians Roadhouse

Okay, so my 2550 started in with a nasty 60Hz hum this afternoon. I had been meaning to replace the 30 year old filter caps with new ARS caps, which I did do. I have the new caps installed, but it still suffers from the same issues. When I plug/unplug the guitar cord, I get a whistling sound at the halfway point. I've never experienced this before with any amp. Doesn't matter if the other end is plugged into the guitar, or not... I still get the whistling. Anyone else experience this? Any ideas what is going on? I cleaned the input with Deoxit, and also changed the preamp tubes... Neither efforts helped. I also tried using different guitar cords.

Perhaps a microphonic power tube?

That's what I found! I replaced the replacement V1 tube with another tube after testing the socket connections.... Fixed! The filter caps original caps needed replacing, so it wasn't a complete waste of time. What are the chances of having two failed 12AX7 tubes? 1 in 3, apparently.

I had a power tube short in my 6100 once and it out three preamp tubes with it. Anything is possible.

Anitoli wrote:I had a power tube short in my 6100 once and it out three preamp tubes with it. Anything is possible.

That may very well be what happened then. Seems like it's a lot louder with the new filter capacitors installed.