Fixing the Reverb Tank

The reverb tank is definitely a weak spot, but its most common problem is fixable if you have the time and patience.

Check the continuity at the tank itself by measuring the resistance at each RCA jack (plug in a jumper cable for ease of access). The input side (towards the center, where the red wire goes) should measure around 60 ohms. The output side (black wire, on the right, looking at the back of the amp) should measure around 200 ohms.

It's not uncommon for the wires that go from the input and output jacks to the reverb transducers to break right where they go into the white plastic push-on connectors. The green and black wires are pressed into the back of the push-on connector, and the connector has an insulation-piercing blade that slices through the insulation and makes contact with the wire. Unfortunately, the blade sometimes nicks the wire and it breaks right there.

Track down the broken wire by looking for continuity with a ohmmeter on each wire, from the pins to the jack. When you find the bad one, pull the wire out of the push-on connector with long-nose pliers, trim the broken portion, and push it back in again with a thin screwdriver so the blade re-pierces the insulation.

If that doesn't do it, the problem may be with the tank itself. The very fine wires from the transducer coil to the push-on pins may have broken. You should have continuity through the pins--If you don't have continuity on both sides of the tank, one of the fine wires is broken. These are very hard to resolder--I have to work under a magnifying lamp to do it.

At this point, you may want to just replace the tank. They're less than $25 from suppliers such as Antique Electronics and MojoTone.

This is the back of the plug that connects the RCA jack to the reverb assembly. Sorry for the blurry picture, but you'll see a pair of knives that cut the insulation when the black and green wires are pressed into the connector. They often nick the wire, however, which breaks. Everything looks good, but there's no connection or it only works occasionally. The fix is to pull the wire out (find out which one with an ohmmeter), trim the broken part, and reinsert it. Push it in with a jeweler's screwdriver or other small blade.

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