Squeeeling amp?!

[cheezemaster]

So I'm sitting here, playing at a low volume thru my little Blues Jr., when all of a sudden SQUEEEEAL.. like nasty microphone feedback - or a stuck pig:eek1:. What gives? I'm thinking (hoping) that it just needs new tubes... I hadn't noticed any issues until now - granted, this is my "practice" amp and rarely use it for gigging/rehearsing - at least I haven't for months. All tubes (preamp and power) appear to be working - at least they're glowing.. As you can tell I know very little about amps. :dunno:

Note: it does this with or without a guitar plugged in and with different guitars, so it's not a pickup or guitar electronics problem.

 

[benji657]

Re: Squeeeling amp?!

sounds like a microphonic preamp tube..

tap it lightly with a pencil to check if it is..

 

[firebirdV]

Re: Squeeeling amp?!

Well if the thing just squeals non stop then I don't think tapping with a pencil is going to be much help. I'd go ahead and change the preamp tubes if you have any laying around, see if that does anything. If you only have one then switch them one at a time (with the amp off of course).

 

[Boogie Bill]

Re: Squeeeling amp?!

It's probably the very first preamp tube--or the reverb tube. Just replace them one at a time to find the culprit.

Bill

 

[cheezemaster]

Re: Squeeeling amp?!

I replaced the preamp tubes with some I had laying around.. and it's still doing it! Of course, these are old tubes, so maybe one of them is messed up too.. who knows? I oughta probably just take it to an amp repair tech...

 

[SlyFoxx]

Re: Squeeeling amp?!

Well if the thing just squeals non stop then I don't think tapping with a pencil is going to be much help.

It's not a fix, it's a test to see if the tube is microphonic.

@cheezemaster

You might still have a bad tube but there's another common cause for what you describe....a microphonic pickup. Pickups whoes coils are not potted can cause squeal if you use too much gain even at a moderate volume. Have you experimented with using say the neck pup vs the bridge pup...or tried another guitar ?

 

[cheezemaster]

Re: Squeeeling amp?!

You might still have a bad tube but there's another common cause for what you describe....a microphonic pickup. Pickups whoes coils are not potted can cause squeal if you use too much gain even at a moderate volume. Have you experimented with using say the neck pup vs the bridge pup...or tried another guitar ?

I initially thought that, but it happens no matter what guitar I have plugged in.. and even when nothing is plugged in. It's definitely amp-related.

 

[WhoFan]

Re: Squeeeling amp?!

my Classic 50 squelled loud when i put new tubes in it... brand new out of the box one was squelling... taping them with a pencil does help you find the the noisey one....