Gregory Reverb 1500?

[Rhodesplyr]

A customer brought me a few pieces of gear for repairs, including a Gregory Reverb 1500 guitar amp, and I took my first good look at it tonight. It's pretty similar to other Gregory amps like the Mark X with the addition of a primitive transistor reverb circuit.

As I inspected it, I got a sinking feeling. I think this is the WORST build quality I've ever seen, apart from an old Heathkit capacitor checker. I'm not just talking incompetent--I'm talking frighteningly unsafe. In fact, I'm wondering if these were sold as kits. This certainly looks like it was built by a raw beginner.

I'm going to have to talk to my customer about this one. I don't know if I want to be responsible for trying to "repair" this piece of junk. I think the only thing it's good for is a complete teardown and rebuild, but I don't know if he wants to pay for that.

David

[Rhodesplyr]

I wanted to post about this amp again with more information and an actual question.

My customer bought it non-working and blowing fuses because he has another Gregory amp that he likes; it needs new power supply caps, which are on order for the right values. It seems to be "OK" other than that except for a small, separate three-transistor reverb driver board that's crumbly and on which all three transistors appear to be shorted.

I sketched out the circuit, no schematic being available, and it's rather bizarre. For example, the cathode resistor for the first 12AX7 gain stage is a pot for the reverb tank return, with the wiper in the DC path of course. In order to try to get maximum gain from two 12AX7s (which are responsible for gain, tremolo, and phase inverter/driver), the designer ran everything at very high impedance without the use of any shielded cable or a fully enclosed chassis. To finish things off, it runs non-twisted heater wiring (chassis used as return) bundled with high-impedance signal wiring.

In short, it hums, LOUDLY (running it with temporary known-good power supply caps).

Also, volume and tone controls operate *before* the first gain stage, so they present highly variable loads to the guitar pickups depending on how they're set.

I could rebuild it making liberal use of shielded cable, better grounding, and heater wiring, but my customer doesn't really know if he'd like it since he never heard it in working order.

The other option would be to rebuild it as something else using the existing transformers, chassis, case speakers, etc... We've got two 12AX7s, two 7189s, and a 6CA4 rectifier to work with--and a reverb tank.

Ideas?

[drewl]

Hahaha......got one of these in and it's exactly how you described it.
This one actually works, but is noisy as hell of course.

The crazy reverb makes some far out noises when you tap on the little reverb driver board.
I'll see if I can talk the owner into having this rebuilt into something good sounding. All the parts are here, just needs a better circuit with better construction.