Peavey Envoy issues

[2n508]

Hi, first time poster here

I recently picked up a Peavey Envoy to leave in the car as a emergency backup at gigs,

It has a few issues:

1. It has no reverb
2. When playing on the clean channel it momentarily drops out if you hit a chord hard, it's fine if strumming
3. The drive channel sounds like a quiet can of angry bees, when you switch over it starts off normal but drops in volume within half a second

Things I've tried/found out:

1. Removed & cleaned reverb tank connectors - no fix
2. Tried known working reverb tank - still no reverb
3. When reverb is bypassed with foot switch the drive channel operates normally, but has the same issue of volume cut out as channel 1.

Thoughts?

Thanks,

Brad

[Jazz P Bass]

Peavey Envoy 110 Schematic

Welcome to the forum.

The Peavey Envoy is a really nice amp.

Let's try to narrow down the 'drop out' to the preamp or the power amp.

Run a signal cord from the Preamp Out jack to another amp.

If the problem persists, then the issue is with preamp.
If not, then you have a power amp circuit problem.

[2n508]

Hello and thanks for the welcome.

Just tried as you suggested, problem is also coming through the 2nd amp.

Thanks,

Brad

[2n508]

Any particular area or component I should be specifically looking at with this?

[Enzo]

You have a meter and know how to use it? Find two large 5w resistors, 250 ohm. Down near the corner where the transformr wires go on. R60 R76. Both should run warm. I don't know what voltages will be there, but I expect someting like 30 at one end and closer to 15-20 at the other of each resistor. One positive, the other negative. after another 100 ohm resistor each, we see 15v zener diodes. Those are the supplied for all your ICs. I am concerned if you have both +15 and -15 at all the ICs. Pins 8 and 4 of each. Once we know we have power supplies, then I go down the ICs and check the output pins of each looking for unwanted DC. The outputs are pins 1 and 7.


And if all that works, I think the first area I'd look close would be JFET mutes Q1, Q2.

[The Dude]

There are obviously problems other than reverb at work here, but just wanted to make a couple of points.

1) All reverb tanks are not the same. There are different impedance tanks. Make sure if you substitute a "known working reverb tank" that it is the same or at least similar, or you haven't proved anything.

2) Checking a tank is not that difficult. Are the springs broken and are the coil/transformers/connections open? That's about it. Broken springs is a simple visual inspection. A quick meter across the input/output jacks will tell you if wires or coils are open. Better yet meter across the wires plugged into the tank and check the RCA cables at the same time.

[2n508]

Thanks for the info, will check this and report back.

You have a meter and know how to use it? Find two large 5w resistors, 250 ohm. Down near the corner where the transformr wires go on. R60 R76. Both should run warm. I don't know what voltages will be there, but I expect someting like 30 at one end and closer to 15-20 at the other of each resistor. One positive, the other negative. after another 100 ohm resistor each, we see 15v zener diodes. Those are the supplied for all your ICs. I am concerned if you have both +15 and -15 at all the ICs. Pins 8 and 4 of each. Once we know we have power supplies, then I go down the ICs and check the output pins of each looking for unwanted DC. The outputs are pins 1 and 7.


And if all that works, I think the first area I'd look close would be JFET mutes Q1, Q2.

[2n508]

Ok,

2 x 5w resistors (r60 & r76) both have 30v input, both reading respectively 19.30v+ / 19.05v-
100k resistors (r61, r77) 14.79v+ / 15.64v- (is this ok?)

Pins 8 & 4 on all IC's are reading as per 100k resistor outputs
Pin 7 on U3 is reading 13.70V+, all others appear ok, is this my culprit? U3 appears to be the reverb driver.

Getting this voltage with the reverb tank connected or disconnected too.

Thanks,

Brad

You have a meter and know how to use it? Find two large 5w resistors, 250 ohm. Down near the corner where the transformr wires go on. R60 R76. Both should run warm. I don't know what voltages will be there, but I expect someting like 30 at one end and closer to 15-20 at the other of each resistor. One positive, the other negative. after another 100 ohm resistor each, we see 15v zener diodes. Those are the supplied for all your ICs. I am concerned if you have both +15 and -15 at all the ICs. Pins 8 and 4 of each. Once we know we have power supplies, then I go down the ICs and check the output pins of each looking for unwanted DC. The outputs are pins 1 and 7.


And if all that works, I think the first area I'd look close would be JFET mutes Q1, Q2.

[Enzo]

Those are 100 ohm, not 100k.

yes, those voltages are close enough to 15v.

Well, that is not what I expect to find on the reverb drive output. So try a different op amp in that location. Were they still using sockets when they made this amp?

[2n508]

Thankyou for the reply,

Right you are.

yes that one is socketed, I tried a known working 4558 in it and it still had 13.7v on pin 7, still has the same issues.

Thoughts?

Brad

Those are 100 ohm, not 100k.

yes, those voltages are close enough to 15v.

Well, that is not what I expect to find on the reverb drive output. So try a different op amp in that location. Were they still using sockets when they made this amp?

[Jazz P Bass]

Can you supply the input pin voltages (5 & 6) of IC3?
No signal, Volts dc.

[Enzo]

The stage with the 13v, check the resistors in it for opens.

[2n508]

Just looking closer I've realized we have been using the wrong schematic, this amp is the 1990 version!

[2n508]

Both are reading -0.471vdc

Can you supply the input pin voltages (5 & 6) of IC3?
No signal, Volts dc.

[2n508]

Which resistors exactly? I've checked the few that I can see have something to do with pins 5,6 & 7 on U3 and they all meter ok

The stage with the 13v, check the resistors in it for opens.