New tube problems or something more?

[jbhights]

Late 2012 Dr Z Maz18 NR

Never had trouble with the amp before but it was due for a tube swap so I did just that - still had the factory originals in there. Ordered a stock replacement set from thetubestore.com. All same brand/model as the factory equipment.

No trouble at first - maybe 5-6 hours on the tubes now. Last week during home practice the amp lost all bottom end and then the volume fizzled out completely. Switched off for a few minutes then powered back up. No problem - back to normal. Last night at rehearsal - same thing. This time I scoped out the tubes before I shut her down. The EL84 in the first socket was BRIGHT red/orange. Definitely not normal and nothing like the tube in socket two - something obviously wrong as the amp had zero volume. Again, shut her down for a few minutes and was fine after a reboot for the remainder of practice.

I'm a player not an electrician - so my knowledge is limited here. Any ideas on what to troubleshoot first? Quick google search suggested leaky capacitors - but wouldn't I have seen that with the previous tube set? Could I have a lemon tube. Anything else?

Big gig coming in two weeks up during halftime of a NBA game, so I want to make sure tubes don't crap out on me! Yikes!!!

Thanks in advance for any help!

Cheers!

 

[Bob Pollock]

Swap the tubes with each other, see if the

BRIGHT red/orange

follows the tube to the other socket, or if it stays with the first socket. this will tell you if it's a tube problem (if it follows the tube to the other socket) or an amp issue (stays at the first socket). If it's the latter, it's likely a bias supply issue with that socket. Also, try putting your old tubes back in. Hope this helps.

 

[DaveKS]

Put your orig el84 back in, see if it goes away. If so they sent you a dud. Call them up and ask for a replacement set.

Ps at a yr and 1/2 old amps original preamps where probably still fine. But at least you got spares now.