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.Originally Posted by Twistedpair
When you touch the two leads of your meter together what reading do you get?
Hello Bill. Let me Check my meter to see what I get....
I read 00.4 with the meter set to Ohms....
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....
Last edited by Twistedpair; 06-27-2012 at 03:53 AM.
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.
Education is what you're left with after you have forgotten what you have learned.
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.
Education is what you're left with after you have forgotten what you have learned.
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....
Strange, that reading at the input is sorta odd then.
Like most guys here, I use Caig DeOxit for pot cleaning
Education is what you're left with after you have forgotten what you have learned.
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....
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.
Education is what you're left with after you have forgotten what you have learned.
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....
Last edited by Twistedpair; 06-27-2012 at 02:49 PM.
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.
"So, for my small experience in the trade I would think that killing customers is, at the very least, bad for business." -Chuck H
Disclaimer: "Take my advice; don't listen to me"-Neil Young. "I'll lie again and again and I'll keep lying; I promise"-Henry Rollins.
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....
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.
"So, for my small experience in the trade I would think that killing customers is, at the very least, bad for business." -Chuck H
Disclaimer: "Take my advice; don't listen to me"-Neil Young. "I'll lie again and again and I'll keep lying; I promise"-Henry Rollins.
The output jack IS grounded to the pan body, the input jack IS NOT grounded to the body.
Education is what you're left with after you have forgotten what you have learned.
The Pan Body and springs are good. Next I will move on to the test mentioned in post #6, However, during my general inspection of the PCB, I noticed that the Collector on Q6 (5884) had been cut from the Board by a repair shop or more likely the previous owner. So before I can proceed with further testing, I will have to resolve this issue next. I also noticed that the Valves (V1-V2) were labeled Sovtek 5881WXT. The cross reference for tubes listed the 5881 as a substitute for the 6L6GC but not the 5881WXT. Were the 5881WXT Valves the right ones and could they have caused problems with Q6 ? Thank you....
[QUOTE=Twistedpair;264800] I noticed that the Collector on Q6 (5884) had been cut from the Board by a repair shop or more likely the previous owner. QUOTE]
Well, with Q6 collector missing, V1 will not work.
I would check Q6 to see if it is good.
There is no reason that I can think of to 'cut' that connection.
And the 5881WXT tubes will work fine ( if they are proven good)
Hello Jazz P Bass. I don't know why Q6 was cut but there is not enough lead left to try and salvage it. I will have to replace it without a doubt. I'm looking for a replacement now but I haven't been able to identify Q6 Yet. Thank You....
Before we go nuts, the tab of Q6 is also the collector. Is there a screw through the tab hole? And is it through a trace on the board? Soldered? Is there continutiy from the tab of Q6 to pins 1 and 8 of V1? If so, move on, it is fine.
They might have trimmed the center leg because the trace underneath was coming loose, so they left the tab to do the job.
5881, 6L6, they will all work just fine in this amp. Don;t make too much of it, the differences are minute. In the OLD days there was a difference, today any current production 5881 is just another 6L6 anyway. And it certainly will have zero effect on the reverb. Focus.
I really doubt your Q6 is a problem. If the amp works, I;d leave it. Those transistors should be replaced as pairs anyway, if replaced. The Peavey 5884 has a factory cross to MJE15028 or MJE15030. And certainly the higher voltage version MJE15032 would also be fine. And anything that works in a Music Man amp would be fine.
But if you have something like 75-95vDC on either the cathode of V1 or the tab of Q6, it is fine.
Education is what you're left with after you have forgotten what you have learned.
Roger that Enzo. I will do those checks today to verify that Q6 is good or bad. Q6 Does have the soldered in Screw. Thank you....
Getting ready to run the #6 Enzo test to check the Reverb unit and Q6 when I noticed that the speaker polarity seemed to be connected backwards. The Tip of the plug is on the negative side and the sleeve is on the positive side. Is that Normal ? Wouldn't that Make the two (212's) speakers push instead pull ?
It does not matter what the speaker polarity is, as long as they are in phase with each other...this is AC.
Out of curiosity, dd you try the simple step of replacing the IC (U6 I believe)? Any old NE5532, 4558, etc will do here.
Hello Nashvillebill. Thank you for your reply. For the two 12's to be in phase with each other means, positive to positive to each speaker ? Haven't determined if U6 is bad yet so I haven't tried replacing it. Also, I don't have a 4558 on hand. My problem with the reverb might be something as simple as the reverb unit connections being backwards. Maybe I will get lucky and not have to order one.
Yep those speakers are in parallel.
You can pull U1 and put it in the place of U6 for a test, see if you hear reverb when you jar the amp. Peavey's opamp reverb drivers have seemed to be a known failure mode, fortunately they are socketed and easy and cheap to replace
Radio Shack sells NE5532 opamps I believe.
Ok thanks Nashvillebill. I will try the opamp swap to see what happens. love those sockets.
Take a little care swapping the opamps around, they are sensitive to static. And make sure the legs go in correctly...hint, when you go to Rat Shack for the new opamp, get their little plastic IC puller/installer for a few bucks.
Ok Nashvillebill, That did it. I have reverb after the opamp swap. Thank you. Just read your review of the Classic VTX on Harmony Central. I have one of those cheap Din Footswitch jacks that needs replaced. Mine is cracked from the previous owner. The VTX didn't come with a Footswitch. I'm going to make a Footswitch for it but I would like to include the Leds as you did with your custom Switch. Where did you tap into for the power to the Leds ? Also, can you suggest a part number or supplier for the Footswitch Din Jack ? Thanks again for your help.
Wow, I had to re-read my review... (there's been a lot happening in my life the last year or so, unfortunately)
Okay, no major updates to my review, other than I did put Eminence Lil Texas Neo's in to save a few pounds of weight, they sound fine. The tubes--I had JJ 6L6GC tubes in there but stumbled across a great deal on a bunch of old tubes, and now there's brand new NOS GE 6L6GC's in there. They sound good too, but I don't hold much crredence to "tube swapping mojo".
Parts Express has the DIN connector. I don't recall the part number, sorry.
Now to make the lighted footswitch: I tapped into the heater supply to get the power supply for the LED's. I rectified the LED power supply to make DC (not the entire heater filament power, just the little bit going to the LED's), I didn't want the LED's to flicker or for any AC hum to come through the footswitch wiring. Next problem: coming up with another conductor in the cable. I realized that two conductors were actually being used for ground, I don't remember which. So I diverted one of the redundant ground conductors and used it. Sorry I can't remember which conductors. The switches themselves were DP.
Wow this is my lucky day. I made notes on the FS conductors and saved it way back then. The notes don't show it but I think either the red or yellow was actually a ground parallel to 1, so that's what I used for the (-) conductor of my LED's.
It's my lucky day too. My VTX is fixed and now your also helping me with a must have footswitch. How much better does it get than that. But as a novice I must ask, the heater tap point is pin 2 of either valve (6.3 vac) and a single diode to convert to dc, and a limiting resistor for each led ?
May I suggest that the amp already has DC supplies in it - the +15 and -15 for the preamp. Clean filtered DC. And if tapping off the preamp supply makes you uncomfortable, they are dervied from +/-27v supplies which you could also use. Only difference would be you wuold have to raise the value of any current limiting resistors for the LEDs. Seems easier than building a new supply to me.
Education is what you're left with after you have forgotten what you have learned.
Enzo, my concern with the +/-15 volt preamp supply was the amount of available current; IIRC, with the Zeners there was only 70 or 80 mA available per rail. Since I had subbed in the NE5532 on a couple of IC's as well as the OPA2134 in the first few IC's, I didn't know how close I was coming to using all of that. I didn't know if the few extra mA from the LED's might've been too much.
So since I had a bridge rectifier handy, and plenty of real estate, I just came off the heater supply since it was nice and close to the FS jack. There was indeed a madness to my method!!
Back to the OP, yes once you have a constant DC, then each LED gets its own dropping resistor. And Pins 2 and 7 on the socket. I kept the DC for the FS totally isolated from chassis ground, IIRC, I did not want to introduce any noise anywhere, so I derived both + and - from the heater supply and did not tie the FS LED ground back to the chassis. Dunno if that was overkill but the FS is quiet.
Looking at the schematic, the 6.3 vac heater supply offers a robust 6 amp supply vs the pre-amp supply of 15 vdc at 1 amp. I'll assume that the 3 leds needed for the foot switch will consume about 20 ma each. Will that 60 ma led current draw on the heater circuit affect it's operation to any noticable level ?
Peavey uses the same power transformer on other amps with more tubes on the heater supply, so it's got plenty of heater current capacity. It won't blink at a few extra milliamps.
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