Tube Amp Maintenance Question (Carvin XV-212)

Those "look" OK. If I were you I would get a known good 12AX7 and begin to swap the small tubes out one at a time and see if you get any change.
Remember that if you open the chassis, DON'T TOUCH ANYTHING... even if it is unplugged and has BEEN UNPLUGGED for a while there are things in there that can kill you. A capacitor can even rebuild a charge after having been discharged. However, if you're comfortable just looking, you might take a look is changing the tubes does not fix it. Look for anything that looks burnt on one end or the other. Look for anything that may have some loose. Put one hand in your back pocket and wiggle anything suspect using a wooden chopstick. Never use both hands in an amp. Taking a picture of the guts or several pictures while being CAREFUL and posting them may get someone to tell you if anything looks wrong or maybe suggest where to check for a loose solder joint using the CHOPSTICK. There are videos on discharging caps, it isn't that hard to do, if you're comfortable giving it a try. If not, get someone else to do it. Just never do it while tired, drinking, or incapacitated in any way. Never forget that it can kill you, ony use one hand, wear rubber soled shoes and you'll probably be fine.
I learned to build simple tube amps from a kit and then from parts and if I can do it, anyone can... just never be careless and use a lot of respect.
I really don't think the problem you are describing could be the power tubes, the big ones... my first idea is that one of the small tubes, probably all 12AX7s has a bad half. Sometimes a half of a tube will be used for extra gain. That would be the easiest thing to try because all you have to worry about is hot tubes, let them cool before you pull them... one at a time. You can also turn it on and up.. and then lightly tap the tubes, all of them, with the chopstick or anything that will tap but not break the glass. See if you get a ringing sound or any odd sound when you tap them. Sometimes you can swap out a 12AX7 to another place in the amp. The first ones, closest to the end are usually the ones that are most critical to your sound. I think left to right looking into the back of the amp. They may be marked V1, V2, etc. V1 and V2 are where you want your most stable tubes and possibly a really good NOS tube, according to the tone you want. Tubes and speakers and the easiest things in an amp to experiment with and can make a huge difference in your tone. Speakers can change things more than you can imagine.
Groove Tubes aren't bad but I'd get some JJ tubes, at least a couple of them for that amp.
I don't know but I bet it will run either el34s or 6L6 tubes... with a re-bias. Does it have a switch for running either EL34 or 6L6 ? A lot of carvins do. You culd probably run KT66 tubes too, if there is room. Have some fun trying things once you get the problem sorted out... I bet it is a 12AX7. You may try just swapping the one on the far right for the one on the far left. If that doesn't fix it. Put the far left tube back where it was and put the tube that you took from the far right end into the second from the left socket. If you don't have extra tubes, I would try that first.
If it isn't a tube it is probably a capacitor or a loose solder joint... but it could be anything.
So again... check the small tubes first. Tap the tubes to see if any make a noise. If you are comfortable with it, open the chassis and look for anything that looks burned. Wiggle wires, lightly with a chopstick with one hand behind your back TOUCH NOTHING IN THE GUTS... it can KILL YOU even if it is OFF and UNPLUGGED. Take some pictures.
Look on Youtube for some tube amp basics videos. There are some for the basics and for SAFETY. Gerald Weber has some for basic safety that are decent enough and are easy to understand.
Really, it is fun once you get started... and a simple Tweed Champ style amp is easy to build and very satisfying. I started with a kit from STF, you'd quickly learn a lot about amps.
Karyn and ampfixer.. and Mike are all good help on here.
 
Good luck.
 
J

mettelus
 
Playability is better than when I first got it! Very smooth operation all around - no jumps in volume at all, and even higher ranges of gain didn't cause issues. I put it on 100% RMS and played through the 0db jack for about an hour and is astounding. The first time I have really used this amp since I rebuilt my guitar in 2012 and they match extremely well. Sustain till the cows come home and the rumble of a tube amp is just "awesome." It plays better than I ever remembered, so I will hold off on tubes for the time being - they seem to be perfectly fine, but the pots were definitely in need of TLC.
 
Again, thank you to all who took the time to help me out. This was the first time I ever did this and it went very smoothly. Your time is most appreciated!

 
To be honest, unless a tube shorted out, the glass cracked and let in air, or the cathode heater died on me, I've never really had any issues with tubes going bad from age.  I opted a few times to buy new replacements and there really wasn't a noticeable increase in anything. I thought there was until one day a few days later I pulled the tubes and accidentally got them mixed up with the originals..... nope... not a bit of difference.   I have a Mesa Boogie and it's the same deal there..... the amp is about 35 years old and the same tubes are in it now as when I was gigging and it sounds just as good.
 
Yup...save your money for some new strings because yeah... THEY do make a noticeable difference.