My '87 Silver Jubilee 2550 hums and whistles! WTF?

Silver Jubilee amps, 2555x 2558, 2550, 2553, 2555, 2525H, 2525C

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MacFangus
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My '87 Silver Jubilee 2550 hums and whistles! WTF?

Postby MacFangus » 14 Feb 2017, 13:45

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.

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Re: My '87 Silver Jubilee 2550 hums and whistles! WTF?

Postby Mike_LA » 14 Feb 2017, 14:46

Perhaps a microphonic power tube?
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Re: My '87 Silver Jubilee 2550 hums and whistles! WTF?

Postby MacFangus » 14 Feb 2017, 15:09

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.

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Re: My '87 Silver Jubilee 2550 hums and whistles! WTF?

Postby Anitoli » 14 Feb 2017, 18:15

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

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Re: My '87 Silver Jubilee 2550 hums and whistles! WTF?

Postby MacFangus » 24 Feb 2017, 13:05

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.

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