Peavey Classic VTX: No Reverb

[Twistedpair]

My Peavey Classic 212 VTX has no Reverb. I started my troubleshooting with the Reverb unit first. When ohming out the coils I'm getting 5.91 Ohms on the Input and 211.4 Ohms on the Output Side. I did those checks at the Reverb Molex connector when un-plugged from the main chassis. The Schematics don't show the specs for these coils. Does anyone know what they should Be ? Thank you for your help....

[52 Bill]

My Peavey Classic 212 VTX has no Reverb. I started my troubleshooting with the Reverb unit first. When ohming out the coils I'm getting 5.91 Ohms on the Input and 211.4 Ohms on the Output Side. I did those checks at the Reverb Molex connector when un-plugged from the main chassis. The Schematics don't show the specs for these coils. Does anyone know what they should Be ? Thank you for your help....

Is it possible that the tank has been replaced, or is it definitly original to the amp? When the drive circuit is designed as this one is, with the input coil in the feedback loop of the driving opamp, I usually see an input coil that reads anywhere between 60-200 ohms. Your 6 ohm reading seems too low to me.

When you touch the two leads of your meter together what reading do you get?

[Twistedpair]

Hello Bill. Let me Check my meter to see what I get....

[Twistedpair]

I read 00.4 with the meter set to Ohms....

[Twistedpair]

I Bought the amp used so I'm not sure if its the original tank....The Tank housing is stamped with the name Accutronics, Geneva, ILL....

[Enzo]

let me be a nitpick. The amp is a Classic VTX, not a Classic 212 VTX. Peavey especially adds numbers to the model name in later editions. For example the "Renown" and the "Renown 212" are two different amps, even though the renown is a 2x12 combo amp.

In most cases, the reverb transducer coils will either be right or they will be open. They don't have much of a way to change resistance. The schematic specifies a 71011114 part number. Is there a 711xxxxxx pasrt number on your pan? Is it an Accutronics pan or the older OC pan? (Made by beautiful women) The Accutronics pans would be 4EB2C1B types. LOok for that number. If you have a 4AB2C1B, that is wrong, the AB pans are for Fender-type tube driven pans.

The thing to do is make sure the pan is right, but also check the amp. Turn the amp on, and reverb up. Now rock the amp back and forth to crash the reverb springs. If you get the sp[ring crash from the speakers, then the return side is working.

If the pan is not open at either end, it ought to make some sort of sound. Make sure the two plugs are not in the wrong jacks. The amp has two circuits - the drive, and the return. The return is simple. Pull the plugs from the reverb pan, turn the amp on and the reverb up. Now touch the tip of each reverb plug with a finger. One should hum, and that is the one that goes to the OUTPUT jack on the pan. If neither hums, you have a return problem. If one does, return works.

The drive is a little more complex. Run a signal into the amp input. I use a feed from my stereo receiver so I don;t have to play guitar while I work. But any signal is OK. Now is ther any signal coming out the remaining reverb cable plug? Scope it, or feed it to another amplifier, or even look at it with an AC volt meter. If there is nothing there, it can;t drive the pan.

When it isn't a open pan, a wrong pan, or a mis-connected pan, it is usually the bad IC, U6 in your drawing.

[Enzo]

Oh, you guys were busy while I was typing. 0.4 ohms on the INPUT transducer is exactly right... for the wrong type pan. I bet yours is a 4AB2C1B. You need an EB, not an AB pan.

Do the simple tests I describede to see if the rest of the amp mreverb section is OK.

[Twistedpair]

Hello Enzo. The Pan is the 4EB2C1B by Accutronics. The Amp is apart for Pot Cleaning but I will try your suggestions after re-assembly. What do you use for cleaning the Pots? Thank you....

[Enzo]

Strange, that reading at the input is sorta odd then.

Like most guys here, I use Caig DeOxit for pot cleaning

[Twistedpair]

I wasn't sure what the coil specs were supposed to be because the schematics didn't list them. However, I did notice that on the Output side of the pan's RCA Jack that one of the coil wires that is soldered to the RCA Jack, is grounded to the pans chassis. That Ohm reading on the Output side was 211.4 Ohms. The Pan Input RCA Jack is Isolated from the Pan Chassis....

[Enzo]

Actually, that jack grounding arrangement is specified by the 4EB2C1B part number. The "C" tells us. Look at the schematic, you will see that neither side of the input coil is grounded.

[Twistedpair]

I saw that the schematic didn't show grounding at the Input/Output coil until after the Molex connector but yet I had a grounded Output RCA Jack on the Pan. Was that done for noise reduction ? Thank You....

[g1]

Any chance that input side reading was 59 rather than 5.9 ohms? (Enzo, the .4 ohm reading was for zeroing the meter).
A 60 ohm DC reading on the input side would be about normal for a 600 ohm impedance, which is what that tank should be on the input side.

[Twistedpair]

Hello g-one....You are correct regarding my reading on the Input side of the Tank. It should have been 59.1 instead of 5.91....I had written it down properly in my notes but I typed it in wrong in my post. Thank you for picking that up....

[g1]

Alright, then the pan is the correct one. If the springs are all still intact, the pan should be good. Refer to Enzo's post #6 to test the amp's reverb send and return circuitry.