Amp issue

Muppet

Muppet

Cat in the Hat
So, I plugged my Carvin Legacy 3 in at practice last night. When I turned it on, there was a whooshing sound that came and faded out. After that, there was a constant hiss and I had to push the volume much higher than usual. Still good tone, though. Did I pop a tube? Is it a cap?
 
I haven't had a lot of tube experience. How would I test that? Can I go to guitar center and buy a set of EL34's?
 
I can, the problem is the stupid LEDs they put in there for effect make it difficult to see. Would this be more output or preamp tubes?
 
Muppet said:
I can, the problem is the stupid LEDs they put in there for effect make it difficult to see. Would this be more output or preamp tubes?
Click to expand...
I'm not sure. Its easy to tell if a tube is wonky though if you can see them.
 
Take a pencil with an eraser and tap on each tube while they're lit up see if they flicker or do anything weird.
 
baimun said:
Take a pencil with an eraser and tap on each tube while they're lit up see if they flicker or do anything weird.
Click to expand...

This would be the first thing I would try. Make sure you call GC before you go to see if they have EL34's. I had power tubes fail on me last week and GC did not have those tube at the store. I eventually bought them at a amp repair shop. I paid a little more be I didn't have to wait. Good luck.
 
Music Center in Kenosha has Mesa matched quartets in stock. Waiting to hear how much this is gonna set me back.
 
Does the hiss change with the Volume knob?

Master Volume?

All channels behave the same way?

These questions can pin-point where the problem may be. Issues that increase/decrease with Volume or Master Volume are usually in the preamp. Issues that don't increase/decrease or that affect all channels are usually the power amp (the Phase Inverter is part of the power amp).

It's always a good idea to have a set of known good tubes on hand, even previous working pulls from an amp.

With preamp tubes, you can use ONE known good preamp tube and swap it out one by one and try and find a single bad preamp or PI tube. PI tubes take a lot of punishment are are a good place to check for "all channel" issues before spending money on power tubes.

You can do the same with ONE power tube, but it's usually only good for diagnoses since you want a matched set for long-term reliability.
 
So no, the issue was not resolved by changing out the output tubes. That's ok, I got the set for 90 bucks and the originals were over 2 years old anyway. I'll keep the old ones as backups.

The problem does not seem to correspond to the master volume. Yes, all 3 channels are affected. Like I said, the tone is great, leading me to believe the preamp is ok, it's just the whooshing sound and the drastic decrease in volume output.
 
Try replacing the PI tube. It should be the 12AX7 closest to the power tubes. If you have to swap it out with a preamp tube and see if the problem goes away or moves to one channel or another.
 
I just picked up a GT 12ax7 at a local music store on my lunch. $24. Full retail, I assume. They saw me comin'.
 
Muppet said:
I just picked up a GT 12ax7 at a local music store on my lunch. $24. Full retail, I assume. They saw me comin'.
Click to expand...

Old picture of my kid. His face says all I can say about that price.
44205_615180726068_7336005_n.jpg
 
Update: I replaved the V4 phase inverter with the new 12ax7. So far, so good. Whooshing sound is gone, low end seems to be back, but the hiss came and went a couple times. It just has to get me through this gig tomorrow night, and then I'll put it in the shop.
 
You must log in or register to reply here.
Back
Top