Changed the tube, it is a very small tank that mounts inside the chassis. These amps are known for the weak reverb.
I notice all the preamps are 12AX7's. I'm sure Mesa knew, or knows, what they are doing, but a general rule of thumb for driving the reverb tanks is to use 12AT7's, which have less gain but produce 10x the current. I'm not sure you can just swap a 12AT for a 12AX. A resistor that biases the tube at the cathode would have to be changed for proper operation.
Then again, my Rivera Quiana has a Hammond 6 spring long tank, all 12AX7's, and the reverb sounds great.
My Carvin Vintage 16, has an Accoutronics 3 spring short tank, 12AX7 as the driver, and the reverb is way mellow or weak.
My 2 Allen Amps, which are heavily Fender based, are designed with 12AX7's as the reverb driver, and Accoutonics 3 spring short tanks. The reverb on these are nice originally, but I ended up replacing the 12AX reverb driver tubes with the 12AT's, a resistor change, and I prefer this a little better.
... I digress
Anyways, enjoy that nice reverb pedal!