Lost Channel 1 (Clean Channel)

[brandeeno]

Hey all,

This is a great forum and I thought I would ask the experts here before I called Mesa with my problem.

I have a 5:25 Express and I just recently lost channel 1. Channel 2 seems fine in both blues and burn mode, but Channel 1 is dead. When I crank the master on Channel 1, I can hear some hissing, but this seems to be normal when I crank it.

I just re-tubed the amp <<<<(Probably something I screwed up).
I put in Groove Tube 12AX7-C. (12AX7-A came out...could this be it?) I then installed Mesa EL-84 power tubes.
Flip power switch on with standby switch in stand by mode. (Let 'em heat up a bit)
After pre-heat, turn amp on and everything sounds fine.
I switch to channel two and play for a few moments.
After that, I switch to channel 1 and then nothing.
Anyone have this problem? Know a solution?

PS
I have been playing around with different cab arrangements. Although I dont think the problem I am having is related to using different cabs, I just thought I would let everyone know just in case their might be a problem there.

 

[EtherealWidow]

If you still have the old tubes lying around put em back in and see if it works. It can't be the power tubes, otherwise it would be both channels. I don't know if just one half of the tube can go bad, but if it can my money is on V2 B. It s the 1st stage for the clean, and the 2nd stage for the O.D. The A side of it is just the 1st gain stage. (For all the others I'm guessing) I really don't know man. For the record, can just half a tube go bad?

 

[MrMason]

Try wiggling the "clean/crunch" switch and see if it cuts in and out, it could be a loose connection.

 

[tmac]

For the record, can just half a tube go bad?

Yes.

 

[brandeeno]

Thanks everyone for the replies.

I installed the old tubes just to see what would happen. The problem is reversed now. I have Channel 1, but no Channel 2.

I gave Mesa a call just a few minutes ago. Hopefully they can pinpoint my problem.

Thanks again for the ideas...

 

[soundchaser59]

I got a complete set of brand new Mesa 12AX7's and installed them. Turned the amp on and the clean/crunch side was completely dead. I reversed V1 and V2, powered back on, and then the blues/burn side was dead while the clean crunch started working.

First thing I did was put the EHX tubes back in in V1 and V2 and the amp worked fine again. I put the Mesa tubes in my Frenzel amp and it went dead. Mesa's "Brand New Quality Checked" tubes were bad. Not the first time, but it was the last time! That is the only time I have ever had a problem with new 12AX7's. Now I use TungSol and JJ almost exclusively, but I also use a few brands of 5751's.