I need some Help from you amp gurus

[GuitarDoc]

I've had an Egnater Rebel 30 head for several years and love it for many reasons. But it decided to be mean to me lately.

It started to develop a high pitched squeal a couple weeks ago which was intermittent for a couple days. Then the squeal became constant and kept getting louder. The guitar sound didn't change (that I could tell), didn't get louder or quieter, nor did it get more distorted or muddy. At first I thought it was just a tube going bad...micro-phonic.

Saturday I decided to finally take care of the annoying problem, so I replaced every tube...pre-amp, PI, and power tubes, with the idea that I would replace the old tubes one at a time to find the culprit by process of elimination.

Well I got a surprise, when I had all new tubes in, it did NOT change the problem at all. Still a loud constant high-pitched squeal. Then it decided to just die on me. Nope, no sound at all. All the front lights work fine (power light, channel lights) and the tubes all light up normally. But no sound! Nope none. Not even a hum.

Now, if it just all of a sudden died, I would suspect a fuse. But I've never experienced a fuse that causes a squeal or that gradually goes bad.

Could it be a tranny or cap?

What say you? And thanks in advance for your expertise.

 

[Demanic]

Re: I need some Help from you amp gurus

I would think that the squeal could have been a cap oscillating before it died.

Sent from my MotoE2(4G-LTE) using Tapatalk

 

[GuitarDoc]

Re: I need some Help from you amp gurus

How do you check a cap?

 

[Demanic]

Re: I need some Help from you amp gurus

Last time I thought I had an issue, I let a tech deal with it. Capacitors can play nasty tricks, especially if you don't discharge them properly.

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[ehdwuld]

Re: I need some Help from you amp gurus

the squeal is an arc across a cracked solder joint
on your tube sockets
touch each solder joint and reflow the solder

to check a cap
you have to remove one leg from the circuit

set your meter to ohms
read the two legs
the meter will start to tick up or down depending on the lead orientation
when it reaches a point it will discharge then start over

if it does this it's good
if it doesn't tick, its bad

not much to them

 

[GuitarDoc]

Re: I need some Help from you amp gurus

Thanks for that info guys. I'll check it out this weekend.

But would a cracked solder joint on a tube socket make the entire amp go mute?

 

[ehdwuld]

Re: I need some Help from you amp gurus

It would depend on where the crack is



*(Sent from my durned phone!)*

 

[GuitarDoc]

Re: I need some Help from you amp gurus

I see. Can't wait to get in there and check things out. I'll let you know what happens.

 

[GuitarDoc]

Re: I need some Help from you amp gurus

Update...

I took it apart and resoldered every tube socket point. Put the amp back together and plugged it in. There is sound now, but there is still some squeal. Not near as bad as it was, but still squeals. enough to be annoying and distracting.

It seams weird that redoing all the tube socket joint would help it but not totally cure it. You'd think that if it helped, that would mean that that was the problem. But, if that was the problem, why didn't it totally fix it?

I'm not so sure I want to monkey with the caps, but I certainly don't want to pay a shop a couple hundred dollars to do something I can easily fix myself.

Any suggestions?

 

[DrNewcenstein]

Re: I need some Help from you amp gurus

While you may possess technical skill with an iron, that doesn't always mean the fix is going to be easy. It would be an easy fix for someone who has done it often enough to make it look easy, but if you've not done it before, or all that often, but you know what needs to be done, it still may not be "easy".

 

[ehdwuld]

Re: I need some Help from you amp gurus

I would think you may have missed one joint.

If you indeed reflowed each one . Then the squeal is still a bad joint just in a different part of the circuit.

*(Sent from my durned phone!)*

 

[GuitarDoc]

Re: I need some Help from you amp gurus

I would think you may have missed one joint.

If you indeed reflowed each one . Then the squeal is still a bad joint just in a different part of the circuit.

*(Sent from my durned phone!)*

I didn't miss any of the tube socket joints. And it's not that I didn't do a good job of reflowing the solder. I have very good soldering skills. Been doing it for over 60 years. There was one joint that I noticed first off that looked suspicious...it was kind of powdery looking. I was very thorough with that one and made sure that I could see the solder flowing down into the circuit board.

If this is caused by a joint other than a tube socket, how would I find it? I certainly don't want to resolder the entire circuit board.

 

[d1dsj]

Re: I need some Help from you amp gurus

This sounds similar to a problem one of my mates had years ago with an amp, it turned out to be the reverb unit in his. Does this amp have reverb?

 

[Darg1911]

Re: I need some Help from you amp gurus

Chopstick.

 

[ehdwuld]

Re: I need some Help from you amp gurus

didn't mean you couldn't solder or were of inferior skills

not judging

can't see your board

 

[GuitarDoc]

Re: I need some Help from you amp gurus

This sounds similar to a problem one of my mates had years ago with an amp, it turned out to be the reverb unit in his. Does this amp have reverb?

Yes, it has reverb. But it doesn't make any difference whether the reverb is turned on or off. And the reverb seems to work perfectly.

 

[GuitarDoc]

Re: I need some Help from you amp gurus

Chopstick.

Yes, I tried the "chopstick test" the very first thing...nothing. All the tubes sounded great, not even a hint of ringing/microphonics from any of them.

 

[GuitarDoc]

Re: I need some Help from you amp gurus

didn't mean you couldn't solder or were of inferior skills

not judging

can't see your board

No, your comments were certainly NOT taken that way. I hope my reply didn't give you that impression or wasn't offensive to you in any way. But thanks for that. I appreciate your concern.

 

[GuitarDoc]

Re: I need some Help from you amp gurus

I made a very interesting discovery yesterday.

I plugged in to do some noodling around and when I kicked on my chorus pedal, that squeal got louder. When I turned it off, the squeal was much quieter...still very obviously present, but not as loud. The chorus pedal is plugged into the effects loop of my amp. So I tried unplugging the "send" and "return" cables from the back of my amp.

The squeal TOTALLY disappeared!

So I figured it must be the tube (or socket) that powers the effects loop, or a poor connection in the return jack (I noticed that it would cut in and out as I wiggled the return cable in that jack.

So I decided to plug into another amp to finish off my practicing and I would get to fixing the amp later.

Then I made the most profound discovery...

I got the same squeal from this other amp...a noticeable squeal all the time which got way worse when I switched on my chorus pedal.

So, now I need to take apart my pedal and see if there is anything I can repair. If not, it's time for another chorus pedal. If this turns out to NOT be the problem, you better believe I'll be back.

Thank you so much to all of you who have contributed and helped me along this journey. I at least discovered one poor solder joint that I corrected and perhaps saved me many hours in the future trying to diagnose another problem. You guys are terrif.

 

[GuitarDoc]

Re: I need some Help from you amp gurus

ps: sorry that last post got so wordy.