Peavey Delta Blues/ Classic 30 Reverb Problem

[Tele Twister]

I'm having issues with the reverb on my Peavey Delta Blues amp. When I first got it I didn't have any issues with the reverb (other than hum when turning it up). Now though when I turn the reverb up/on, I don't hear any reverb, but also occasionally the sound will kind of cut off and on/get "static-y" for a second or two.

What do I need to do? It looks like the leads going into and out of the tank are secure (these are soldered on wires, not the RCA ends). Is it possibly an issue with the wiring to the PCB? I haven't taken the chassis out yet. It likely isn't an issue with the reverb tank itself, is it?

Any help would be appreciated!

[Don Moose]

According to the C30 schematic I have, this reverb uses a solid state drive and recovery circuit powered from GND and -30VDC (U1, pin 4 == -30, pin 8 == GND) with a -15VDC bias to the op-amp (+) inputs (U1-3 and U1-5). See how those look, preferably with a scope.

My suspicions would be:
- poor solder in the reverb recovery stage or its power supply
- poor solder in the reverb driver stage or tank wiring

If you give the amp a good smack, do you hear any reverb 'sproing'?
If you get sproing, the reverb return wiring and recovery stage are OK.

Don't suppose you have a similar tank handy? - some other amp with a similar drive/recovery.

Is the cutting out and static something you get ONLY with the reverb on or up?


Hope this helps!

[Tele Twister]

I'll take a closer look tonight. Thanks for the suggestions.

[baddog]

I recently had a similar problem with my Crate VC50 and it turned out to be the IC chip for the reverb section. I had a hum or amplified sound when i turned the reverb up. Although I did have a faint reverb sound when it was turned up all the way. I hope I helped

baddog

[Tele Twister]

Ok, I took a "closer" look at the reverb last night. Closer, for me, meaning I looked at the wires and the solder joints on the reverb tank and fiddled with it a bit . I'm probably a little out of my league here.... I have very basic soldering/electronics skills. I can build stompboxes as long as the directions are good (schematics can be confusing still).

Anyways, there is definitely no reverb present whatsoever when I turn it up. Nothing. When I was looking at the wires everything was very crackly and made lots of pops (I assume this isn't normal). Also when I gave it the "amp smack" check I did not get the sproingy sound. There was just more of a static/rice crispies boom.

So if that is the case, is it safe to say the problem is with the wires?

If/when I take the chassis out and feel too nervous about doing this myself, what do you think be a fair estimate on what it would cost me to have it repaired (assuming the problem is bad wiring/solder joints).

[Alex R]

Most problems with spring reverbs are in the pan itself. Sounds as if you have return amplification, but just check by pulling out the plugs from the pan (I think they will be little domed metal plugs with solder on, but they should still pull off the tank). One jack - the return - should give a healthy buzz through the speaker that you can turn up and down with the reverb knob. If you have another amp, connect the other (send) plug to its input with the volume down very low - just touching the pin to a lead jack tip will do. If you have an effects return or line in use that as the reverb send signal is quite powerful. If you can then hear your guitar thro the other amp, you know the problem is in the pan.

Take out the pan. Look to see if any of the fragile little wires are broken - these you can often resolder or join. If you have an ohmmeter, see if you have reasonably low resistance between pin and screen of the input and output sockets. If not, might be a bad connection you can fix, or a bad coil you can't fix, in which case a replacement pan will not be too expensive.

[Enzo]

After checking the pan, it sounds to me like the littel chip in the amp died.

[tubeswell]

Yep I had that happen to me once as one of the other posters said - (same staticky crap) turned out to be the reverb IC, which is that little 8-pronged black IC chip thing sort of in the middle of the top PC board (the only one in the amp). It is called an op-amp (dual op-amp 8 pin configuration) and they don't cost much to replace (about $3.50 NZ). The chip simply slides out and back in, making sure the pins are lined up with the holes, and the op-amp is the right way round - it'll have a little circle stamped at one end, so put the replacement in the same way. The stock one is a 4558, but a TL072 is a perfect (if not slightly better?) substitute. But as Enzo said, unplug the Reverb tank cables that come off the main pc board first, and check them with your meter probes, just in case its a bad cable/connection. You should have a direct circuit on each pair of wires (when you stick your meter probes into the pb board-end reverb cable plug).

[Enzo]

Here in the USA, a 4558 or similar can be had from Mouser or someplace like it for under 30 cents.

[Tele Twister]

A quick verification on what Alex R was saying about testing return amplification/pulling the pan plugs. The only other amp I have is one of those Marshall MG10 practice amps. Will this work for testing this out? If I understand this right (connecting the send plug to the practice amps input) I can just touch the send plug to the input jack, correct? Or am I understanding that wrong?

Assuming I am getting return amplification, my next step then is checking the reverb pan itself for problems as described.

If everything checks out there I move on to the reverb IC.

I probably won't be able to get to this until this weekend, but I just want to make sure I have all the steps down.

Thanks everyone for taking the time to explain all this to me!

[Alex R]

Yes, should be ok with the little Marshall, just try tip-to-tip for a quick n dirty test. Hum galore etc but you'll hear whether there's a guitar sound there driving the springs, or not. Reverb sends are amplified to something above line level so it's quite a powerful signal there, or should be, but not hot enough to toast anything. It has to have a physical effect on the springs, remember, by activating a little coil. Turn the Marshall down to zero, touch the tips, strum, then turn up by tiny bits till you hear something... or not.