05 January 2015

Another Mesa Lonestar Reverb Problem

Fig. 1. A Mesa Lonestar Special with a bad reverb tank.

I have only repaired two Mesa amps in my life. Both were Lonestars, and both had the same problem: the reverb wasn't working. On the Mesa I fixed last summer (the Purple Beast), the problem was a broken wire in the tank and an pretty easy fix.

This time, the symptom was exactly the same. The first thing I did was look all over for the reverb footswitch input, which is unmarked and tucked away under the chassis, behind the reverb cable jacks (see Fig. 2). Once I had that hooked up, I checked that the reverb controls were turned up and that the tank was correctly connected (which I did by reversing the wires and still not getting any reverb). I checked the wires for continuity and tried new ones just to be absolutely safe. Still no reverb.

Reverb Footswitch Jack
Fig. 2. Here I am pointing at the very well hidden reverb footswitch jack.

I had my kids check for continuity in the tank (Fig. 3), and everything checked out. I then plugged the tank into my Blues Jr, and there was no reverb. I had a new one ordered ($20) and waited.

Fig. 3. The younguns having a go at it. Specifically, checking for continuity on the wires in the tank.
When the new one came, I was excited about the quick fix (the sooner I fix it, the happier the customer is, the quicker I get a $1700 amp off  my property, and the sooner I get paid). I quickly installed the tank and tried it out. No effing reverb. I switched cables, tried it in the Blues Jr.—still nothing.

I thought I should take a peek at the allegedly new reverb tank, so I removed it from the plywood it was mounted to. I had glanced at the inside of the tank before screwing it to the plywood before, but I missed an obvious and important detail: the reverb tank was shipped with a small piece of foam packed under the springs, which prevents them from rattling when shipped and from creating a reverb sound when installed.

With the foam removed, I installed the tank and tried the amp, and it sounded heavenly.