HELP! - Dual Rec Lost all Volume

[fleeced]

Hi, - Please help!

Had what I thought was a pre-amp tube problem at a gig on friday night ... after swapping them all it wasn't cured ... I ended up doing the gig with guitar into the "return" of the effects loop (which only uses the power amp stage of the amp) and with a OD pedal my only OD ... I got through the gig but hated having lost all my sounds.

At home today I have swapped all five 12AX7s out - and there's no difference.

With guitar in the input, the channels still seems to work (Ch1 is clean Ch2 crunch etc.) but even with the amp up to full volume you can only just hear it.

Even though I know it's not the power tubes I've swapped these out too just to eliminate them.

Please Help!!!

The pre-amps seem to be working from a gain/tone point of view - but absolutely no volume - even with the power amp turned right up.

When I just use the power amp I get volume.

All the pre amp tubes have been swapped. Effects loop on/bypassed makes no difference. Footswitch or channel switch makes no difference, (to the volume at least). Diodes/tube switch makes no difference.

What is the problem? - Is there another "driver tube" somewhere I don't know about? Is there some resistor that's burned out?

Any advice appreciated

 

[fleeced]

....with the overwhelming silence in response to this one ... I guess everyone's as stumped as I was ....

The amp has now been sent off to a tech ...

As the problem sounds so much like a pre-amp tube, yet isn't a tube as I've changed them all ... I reckon it's a bad connection on one of the pre-amp circuits ... a dry joint or something.

The consensus among the guys in the guitar shop was that I was probably right ... but we'll see what the diagnosis is when I get the amp back .... Got a gig in 10 days so I hope it's quick!

 

[Old BF Shred]

Does you preamp have full output?
May sound like a "duh" question, but have you tried to run another power amp with the loop 'send'?

At least you'll know if it works up to the loop 'send' output......
Did something "Happen" to the amp prior to the problem? (you did not say).
Did it happen all at once? did it happen gradually? Jacks and plugs, whether input or on the fx loop, are notorious for building up dirt and developing corrosion, leading to similar symptons.

Are all modes/channels affected?

Just food for thought as you'll know when it gets back.
Hope it's something simple and inexpensive!
Good luck!

 

[stephen sawall]

Did you change the tubes one at a time or all at once ?

 

[fleeced]

Did you change the tubes one at a time or all at once ?

.. two at a time (I had 2 new tubes) ... Ended up replacing them with the originals before taking it to the tech. .

Just heard from the tech and the verdict is "3 pre amp tubes bad".

I'm glad it was something simple ... but am concerned as to what on earth could cause three tubes to fail at the same time. As I've asked in another post - could putting a Tung Sol in V1 have caused it? - Not sure on the bias ratings. Could one tube failing have caused two others to fail?

Does you preamp have full output?
May sound like a "duh" question, but have you tried to run another power amp with the loop 'send'?

At least you'll know if it works up to the loop 'send' output......
Did something "Happen" to the amp prior to the problem? (you did not say).
Did it happen all at once? did it happen gradually? Jacks and plugs, whether input or on the fx loop, are notorious for building up dirt and developing corrosion, leading to similar symptons.

Are all modes/channels affected?

Just food for thought as you'll know when it gets back.
Hope it's something simple and inexpensive!
Good luck!

It happened suddenly ...

I had pretty much eliminated everything else ... tested the power amp through the return of the effects loop (that's how I got through the gig) ... the pre amps all had the "tones" but absolutely no volume. FX loop on, jumpered or bypassed made no difference. Bold / spongy... - diodes / rectifiers made no difference.

Thanks very much for the replies -any clues on why 3 tubes went at once appreciated!!!

 

[stephen sawall]

When looking for a problem always do one tube at a time.
He may have put it on a meter and found them to low for the application.
Could have been 1 tube and he is selling you 3.
Ask him for the old tubes.
Don't worry about it if he does not have them.
If you did not tell him this before hand you have nothing to get mad about.
Make sure just like a car that you get all the parts and they are the same parts. Right down what it said on the tubes / car parts before you give it to them..... etc/pictures.
I have seen people re tube a amp for someone saying they need to be replaced and then put most of the tubes in there own collection or sell them to the next guy.
Most people are pretty straight up and just threw them out......

If you have not tried the tube in a other amp even if new you cant tell if there bad.....

 

[fleeced]

well the amp is back ... and working fine ........ I can only assume that age took 3 tubes down at the same time ... (maybe one going pushed the other two??)

It definitley wasn't one tube (I had swapped them all out ...) ... but it could be one of those mysteries that isn't worth worrying about now the problem has (hopefully for good) gone away...

I have a Tung Sol back in V1 .... and the amp has done two gigs and several rehearsals and (fingers crossed...) seems to be fine.

I must admit to breathing a sigh of relief every time i take the amp off standby for the first time and .... it works .. !!

Thanks for the advice ...

 

[stephen sawall]

Good to hear.

 

[fluff191]

Wow Im glad I found this post. I am having the EXACT same problem with my Dual Recto. I put 3 EH 12ax7's in the first 3 positions, and now those 3 are not lighting up at all. All seemed to have stopped working overnight. Wierd. :idea: