Reverb not working in Express 5:50 1 x 12 combo

I just noticed the other day that the reverb is not working on either channel on my Express 5:50 1 x 12 combo.

Otherwise the amp sounds fine.

I swapped V1 and V5 and the reverb started working and the amp still sounded fine. I swapped them back and the reverb didn't work again. I whacked the top of the amp with my hand and the reverb worked again. Now it's not working and whacking it doesn't help (though the amp still sounds fine otherwise).

I have also swapped in two of the preamp tubes from my Vibrolux Reverb without luck.

I connected another reverb pan that I know works. That didn't help.

I have cleaned all of the connections without luck.

I have noticed that if I rock the amp, I can still hear the reverb "crash" through the speakers.

Hi,

With my limited knowledge of electronics, I would say it may be the tubes.

One thing you could try is call Mesa and speak to CS. There is a fella there named Mike Taylor and I am sure he will provide a way to a solution for you. Is your amp under warranty for the tubes?? If not I have seen a number of threads for Dougs Tubes. You might call there and ask for an opinion.

Good luck,

Nubbs

"everybody has ablitity, but pride in performace is what makes the difference".

I copied this thread sometime ago from the board for future reference. This was from one of the guys that had a problem with his reverb. You could check this out.

Found it, and fixed it.

I talked to MESA about it first and they said that the failure rates on the tanks is very low, so I should check the connector wires really well.

I put the meter on everything, found an open circuit, determined it was in the tank, and investigated further.

Inside the tank, at each end of the springs, is an elctro-mechanical connector. I'm reasonably sure that these things work as follows: the input side converts the electrical signal into a magnetic field, which basically "shakes" the springs at one end. The mechanical resonance travels the length of the springs to the other end, and caused an armature to move inside of the other electro-magnet. This causes current. Which travels back to the amp.

Well, one of these electro-magnet items had its ground wire popped off (it looks like it's 24 gauge - VERY thin). I resoldered it and I swear that my reverb has never sounded deeper!

The thing is that my reverb actually "works", it's just not being applied to the guitar's signal.
If I rock the amp, the tank can be heard crashing through the speakers.
I have also tried a different tank with the same results.
I have also tried new tubes with the same results.

Something is wrong inside the amp. It's going to a service center. Hopefully tomorrow.

It turns out that it's the tank itself. The output on mine reads open on the tech's DMM. All of the connections are good. Mesa has shipped a new tank under warranty. The tech said that his contact at Mesa said that there has been an issue with the tanks.
I have my amp back until it arrives.

I had a bad tank in my old marshall. no wires were visibly broken or anything sometimes stuff just goes bad. at least a new tank is only $20 or $30

The new tank was installed last Wednesday and I'm back in business. It sounds great and was completely covered by the warranty!