Should I recap my amp?

[theendofthegame]

Hi!

I just got a new amp - a music man 112 sixty five. It's pretty old, mid- late-70's.

The amp is very quiet at first, but after a while it starts to make weird noises. It's a quiet sound, but very highpitched - it just annoys me, cause it's a very silent amp otherwise. The noise seem to come and go, I don't know what's causing it... could a recap help?

How often should you recap? And what are the benefits? I've read a little here and there in amp reviews and forums that people recap their amps, especially if they're old amps...

Is it easy to do a recap? Or should a professional do it? (I know how to solder, I've changed pups and caps in my guitars many times... not that I'm very good at it! But I can do it.)

BTW, the tubes are telefunken el84, which was a nice bonus - I think I'd rather do a recap than to change the tubes, and maybe it's time for a recap if it's never been done before?

Other suggestions? What else could be causing noises like that? I don't think the previous owner used the amp much... maybe it just needs some time? I dunno.
:help

[markb]

Whistling noises are not good. Take it to a pro and get a cap job. Get the valves tested at the same time, he may have some good replacements if they're needed. The bias will probably be off too. These amps are well worth treating to a service. They're really good workhorses and love pedals.

[tunghaichuan]

What Markb said.

Take it to a professional. IIRC, the plate voltage in those Musicman amps is 700v. That can kill you dead in a hurry.

They also have an odd circuit using transistors to drive the cathodes of the power tubes.

[theendofthegame]

Whistling noises are not good. Take it to a pro and get a cap job. Get the valves tested at the same time, he may have some good replacements if they're needed. The bias will probably be off too. These amps are well worth treating to a service. They're really good workhorses and love pedals.

"Whistling noises" is the right word to describe the sound, thanks! :) In what way is it not good - just that it's a annoying sound or could the amp be in danger of breaking down?

Would a cap job improve the tone or alter the tone in any way?

BTW, I've been jamming with a friend all weekend, I used the music man amp and didnt notice the noise at all... weird!

[theendofthegame]

What Markb said.

Take it to a professional. IIRC, the plate voltage in those Musicman amps is 700v. That can kill you dead in a hurry.

They also have an odd circuit using transistors to drive the cathodes of the power tubes.

Thanks for the warning, I better stay away from it. My soldering method is usually to try and try again untill it works, so...

[markb]

"Whistling noises" is the right word to describe the sound, thanks! :) In what way is it not good - just that it's a annoying sound or could the amp be in danger of breaking down?

Would a cap job improve the tone or alter the tone in any way?

BTW, I've been jamming with a friend all weekend, I used the music man amp and didnt notice the noise at all... weird!

Your power smoothing caps are out of range. The high pitched noise is induced in the audio circuit. Low tones can happen too, like a bad note or string talk below the low E. These noises will come and go. A cap job is cheap. If they fail they could take the power transformer out too. This will be expensive.

Tung, thanks for reminding me about that weird MM phase inverter circuit. Another good reason to leave these to an expert.