Maz 18 NR Volume and Bass drop.

[krob81]

I picked up a 2012 MAZ 18 a little less than a year ago. Looks as good as new, and sounds great! Has an air brake installed in the back. A few days ago I experienced a dramatic drop in volume and bass frequencies are almost gone. Even with air brake bypassed it is way quieter. I assume it's the power tubes going out. Anyone else with experience with this? If it is the power tubes, should I replace the rectifier as well? Or am I off base?

[John]

My guess would be power tubes. (although I wouldn't be surprised at a pre amp tube)

As for the rec....I doubt it. They either work or they don't and they don't really have an effect on tone. (correct me if I'm wrong guys)

I would replace power tubes asap. You don't want to wait until they actually burn up and self destruct. They can take out rec tubes, fuses, and maybe a few resistors. (Ask me how I know)

[krob81]

Thanks for the tips. I suspected the power tubes, but wasn't sure. I just fired it up again and looked at the tube glow in the dark. It appears one of the tubes is starting to cherry up. I will replace the power tubes. Thanks again.

[John]

Personally, I wouldn't turn the amp on again until you've installed new power tubes.

[Jaguarguy (Mike)]

Here's some information on troubleshooting from Doc's site.

drzamps.com/info/faq-troubleshoot/

[easyed]

I'm no tech, but I've experienced, "a dramatic drop in volume and bass frequencies are almost gone" in another amp. It turned out to be one of the EL84's sitting crooked in it's socket.

I would start troubleshooting by replacing the existing pair of EL84 (or 6p14p) tubes with your spare (backup) set. Cleaning the sockets would be a reasonable thing to do while you're at it.

One of your power tubes may have gone bad, a dirty socket, or just a tube getting loose in it's socket may be the problem, but clean sockets and a fresh pair of power tubes is the first thing I'd try.

If the problem persists, go through Dr. Z's video on troubleshooting your amp.