NEW Peavey Classic 50 Reverb Problem

[nevetslab]

I just got one of the new Peavey Classic 50/410 Amps in with NO REVERB from our rental dept. Pulled the tank out of the floor-mounted pouch, checked the DCR on the two tank coils, finding around 210 ohms on the Output, and 80 ohms on the input. Tank type is a Ruby RRVLEB2C1BV4. My schematics for the Classic 50 are dated 1993, so not current, but after finding the tank seemed ok, I pulled the chassis from the cabinet and moved it to the test bench. The other end of the right-angle RCA cable are also right-angle, plugged in all the way below the front panel, and are inaccessible without major disassembly. I also see in that vicinity a surface mount dual IC, surface mount electrolytic caps, surface mount Q1, presumed to be the muting output FET.

So, while unable to measure and see if it's a cable issue, I instead set up to drive the amp and see what I get from the SEND signal down the cable, and then Drive the Return end of the cable to see if I get signal into the amp thru the Reverb pot. I got signal back thru the Return path, though it behaves as though there is a hard clip limiter on it, though no such circuit seen on the older schematic I have. The Drive signal to the tank, I wasn't seeking any signal, until I removed the low side of the RCA from Ground, and then I saw plenty of signal, Floating (coupled thru my diff input of the Amber 3501a Audio Analyzer). I went to check the Tank, finding the Input of the tank's RCA totally floating relative to the tank chassis, while the Return side's RCA is GROUNDED to the tank chassis.

On the older schematic, the Drive side of the circuit is NOT AC coupled, with the 4558 biased between Ground (Pin 8) and -27V (Pin 4), so the output on that would be half-way negative. On this amp, I'm seeing AC coupled output and input, so NO DC potential present, once charged up.

So, I'm seeing drive and return signals on the Reverb circuit. Plugged tank back in with the attached cables, and still have no Reverb function.

What am I missing here? The Foot Switch doesn't appear to be involved...at least not when the tank is connected. I forgot to check it with driving the Reverb Return side cable to verify the foot switch works. Usually, default with no pedal attached would be Reverb is Present.

I suppose this amp is under warranty, so I could feasibly throw my hands up in defeat and tell our Gtr Dept to send it out to the local Peavey Warranty Service station. Not my style, but, might be the easiest option.

[Enzo]

What am I missing here?

At least: the proper schematic. Call customer service at PV and get the right drawings. Takes a few seconds and often as not you get it within ten minutes of hanging up.

If it has warranty, why not? Point of pride is getting the job done efficiently, not proving to yourself you can fix everything. Surely there are enough challenges lined up.

[Jazz P Bass]

CALL Peavey and obtain the proper schematic.

[nevetslab]

At least: the proper schematic. Call customer service at PV and get the right drawings. Takes a few seconds and often as not you get it within ten minutes of hanging up.

If it has warranty, why not? Point of pride is getting the job done efficiently, not proving to yourself you can fix everything. Surely there are enough challenges lined up.

As usual, you're absolutely right. I'll call Peavey in the morning, as well as find out the warranty situation from our Guitar Dept mgr. Trying to take this one apart doesn't look like any fun at all!

[nevetslab]

How do you extract the main pcb from this chassis??

CALL Peavey and obtain the proper schematic.

I called Peavey when I got back from watching How To Train Your Dragon-Hidden World, just to start my day (last day it was here in the local theater), and got the schematics. The chap I was speaking with had never taken one of these Classic 50 chassis' apart to extract the main PCB. I started in on that, then halted quickly, realizing all I was doing was removing the bent chrome dress panel from the same shaped chassis, which wouldn't accomplish the task. I'm usually good at tearing things down and figuring out the sequence, but this one.......I can't even see how it was put together. There are standoffs (10 of them) supporting the PCB, screwed in from below the chassis and thru the PCB. As the pots are long-leaded spiders, with their bushings/shafts protruding thru the folded over U-shaped-panel, from below (main chassis floor), rear panel, then folded back over for the control panel surface, the PCB assembly is positioned in the center between the legs of the pots and the standoffs from the floor. You can get at the ones across the inside rear of the PCB, and the ones nearest the two ends, but, once you're past that, there are the bulk of the standoffs far into the center of the chassis out of reach. Remove the screws from both sides, the standoffs drop down, and, from what I can see, you'll never get them back into place to reassemble it.

Plus, there's six phone jacks spanning across the bottom below the middle of the PCB, also PCB mounted, so that has to be extracted, as it also prevents dropping the main PCB down into the depths to get the pot bushing/shafts below the surface to try and pivot it out. That's as far as my feeble brain has taken this. You can see the black screw heads on the top of the main PCB.

It appears the Return circuit of the reverb tank is bad....surface mount NJM2114M dual op amp, along with a MMBFJ11 N-Ch JFET switch (mute switch) that follows the output of the op amp. Output is AC coupled, input to the reverb tank is floating (RCA jack not grounded), and that op amps is DC coupled, output at -14VDC on both tip/sleeve of the RCA Jack). You can see the reverb circuitry (all SM parts) in the last photo, nested near the edge of the PCB, well out of probing distance.



Classic_50_II Schematics.pdf

[g1]

I'm guessing your original instincts were correct, and you will have to disengage the faceplate to get enough clearance to finagle the board out of there.

[nevetslab]

Disassembly of the classic 50 ii to extract main pcb assy

I'm guessing your original instincts were correct, and you will have to disengage the faceplate to get enough clearance to finagle the board out of there.

This morning, not willing to be defeated, I pulled the protective tube cage off the bottom of the chassis, unplugged the fan wires connector to get it out. Removed the tubes, keeping them in order, set aside. There were two openings below, one exposed by the absence of the cage, the other had an additional panel to be removed. That exposed the two phone jack PCB assemblies, the rubber hole grommets for each tube socket, and revealed access to all of the internal standoffs that would have to be removed. 5.5mm open end ignition wrench req'd, along with bent-nose pliers.



That only took an hour and a half, taking time to photograph the steps so I'd have some chance of remembering how to put it all back together. Of course the tank cable measured fine. I haven't yet begun troubleshooting the return circuit. I did find stock on the NJR2114 SM Op Amp, but no stock on any of the J111-J113 SM parts at Mouser. Hopefully that part is ok. This reminds me of having to change spark plugs on old Volkswagen Beatles, having to drop the engine to get at the spark plugs!!

[nevetslab]

Broken Reverb Pot

With the main PCB out, I was able to power up the Reverb circuit and verify the Dual Op Amp was working, as well as the Mute FET working. I got signal thru the Op Amp, to the Muting FET, but not past it until I plugged in the FootSwitch Jack, then had it to the top of the Reverb pot, but nothing on the wiper. Well, make that the terminals where they swage them onto the phenolic board containing the resistance track. When I removed the pot from the PCB, it came off in two pieces:



That will stop the Reverb from working for certain! Of course I don't have one on hand (just a 100K Audio Taper pot, same form factor). 10k Linear pot, so now to go order one.

[xtian]

Geez, what a feat of engineering. Count your blessings--I'm happy you could power up the board with it out of the chassis!

[nevetslab]

Reassembly of this chassis, now with replacement pot installed is NOT USER FRIENDLY!! And, just to teach you a lesson, the Lead/Normal Switch broke while tightening it up ???!!! There is a lock nut below the surface, so force cannot be applied below the nut, where a spacer sits between the nut and the switch body's PCB mounting support frame. I had the tiny switch body properly oriented, installed the panel lock washer and nut, and while tightening, the switch bushing pulled out of the body, ejecting parts from within the switch! I do so love these little distractions!

I had only begun getting the PCB assembly's pots poking thru the spring-loaded chrome panel. Getting the panel back in wasn't too difficult. That Difficult part was next. Getting the 5.5mm hex standoff's back onto the PCB. As it turned out, it was easier to get them onto the chassis first. The chassis screws are the same thread/pitch, but smaller dia head than that of the PCB screws. And, as there was thread-lock compound on all of them, so you had to first fumble with each screw & standoff to find which end threaded best with the chassis screws, and drive the screws all the way in, then back them out. Then, holding the part with bent-nose pliers while trying to position the standoff so you could drive the chassis screw thru the obround hole into the standoff......not a chance. You're trying to get that part past the tube socket, while still holding the standoff in an orientation that can fit between the PCB and chassis, which continually slipped and the standoff escapes, taking a football bounce when it hits the table surface below (chassis positioned vertically, fishing these thru the chassis side tube holes). I may have come up with new cuss words in the process!

Getting the PCB back into place and then slipping the shaped rubber grommets to line all the chassis tube opening holes was much easier, though they too didn't want to fit without grief. I then got the wiring re-connected. I did of course remember to install the ribbon cable that connects to the four jack PCB (output, footswitch PCB).

I then turned my attention to the recovered parts of the toggle switch. I de-soldered the switch body from the tiny PCB board, then took a close look to see if there was any way to put it back together. I'll call Peavey in the morning, as this part, while one CAN create a mfgr P/N from a C & K 7000 series catalog, that only creates a factory special part, 1000pc min, 90-180 day delivery. Somehow I managed to recover all the pieces, was able to put the two contact bars back into the switch body below the nylon actuator that gets driven by the captive toggle with a spring-loaded pin. The switch body ended up with a hemispherical dome when it pulled apart and exploded, so I had to come up with the right combination of socket-drive tools to press it all back together in a vise and verify I had a functional switch that could be held back together....JB Weld glue mixed up and applied to the reassembled switch for added strength, so I won't know until tomorrow if this will suffice. It probably will, as the toggle is not a stiff-switching force part.

What A PITA!!!

[nevetslab]

Never ever allow screws to re-engage cage nuts!!!

So, the JB Weld Epoxy cured, the restored original Lead/Normal Switch works, and I soldered it back into it's little PCB, did my best to orient it onto the board, then installed it into the chassis, where it fit in what appeared to be the correct orientation. Guess what? I never did take a picture of how it was positioned before I dismantled everything, so now, I had a 50-50 chance on that switch working as it should



Not so pretty as it once was, but, it works and didn't self-destruct on the installation. Now, in my haste to see if everything was working, I moved the chassis back into the cabinet. What's the rule with screws that came out of cage nuts? NEVER, NEVER EVER ALLOW SCREWS TO RE-ENGAGE CAGE NUTS!!! Marshall and Ampeg have that rule down pat! And, ALWAYS make the chassis width equal to the width of the covered cabinet, with protruding fingers of cage nuts sticking beyond the width to disallow all attempts to re-install the chassis into the cabinet! That took forever, as my arms and body was beginning to wretch in protest while the chassis wanted to go anywhere but where a screw might find a home. I did manage to get the top four screws engaged. Then the side screws. The number of screws had now dwindled to 4, and cycling thru them to get one side engaged. That left the other side. Cabinet hole and cage nut location not in alignment. Figures Neither screw wanted anything to do with those cage nuts. Another 5 minutes of attempts, adding a bar clamp, loosening all of the other screws, swapping screws, I got one engaged, but the last one......not happening. Ran a tap thru the cage nut, then tried again. The chassis screws are NOT #10-32, but M4! Idiot!

I finally got the last screw back in, powered it up to see if the Reverb worked, and if the Lead/Normal Switch worked correctly. Reverb works. The switch is BACKWARDS!!! Congratulations!! I have to pull it all apart again!!!

Pulled it apart again, reversed the switch so it's working correctly. Ran my M4 tap thru the two left side cage nuts, which were the ones giving me the most grief. Not a friendly chassis to get in and out of the cabinet, nor do the cabinet holes align well with the side cage nuts.

But, all is back together & working. 17 hrs to find my way into, thru and back out on this amp.

[Jazz P Bass]

I would make an attempt to contact someone at Peavey.
It sounds like they handed over the design to some dufus in China.
They really screwed the pooch on this one it appears.

[nevetslab]

I would make an attempt to contact someone at Peavey.
It sounds like they handed over the design to some dufus in China.
They really screwed the pooch on this one it appears.

Funny you should mention China:



Having come from Manufacturing since 1974 thru 2003, this product doesn't rate very high in being one that takes very little effort in assembly at all stages to get from start to finish. I'd hate to think how Authorized Peavey Service Centers deal with this product, assuming Peavey has fixed the max labor hours the repair would take. One of their service centers is right down the street from us (CenterStaging, LLC), and I've seen their work before. Doesn't instill much confidence in their abilities. The other one.....I wouldn't have felt good putting this one onto their plate, as they do excellent work, but would hate us if they accepted this task.

I might send Peavey the link to this thread, having made contact with one of their chaps in Service (who I got the schematics from).

Note: I had just posted this reply, and never found it came up in the What's New listing. So, did it again.

[Leo_Gnardo]

Having come from Manufacturing since 1974 thru 2003, this product doesn't rate very high in being one that takes very little effort in assembly at all stages to get from start to finish.

What I have to tell crustomers about their cheaply made amps especially over the last 30 years: they were designed to be assembled quickly by low-talent labor and/or robots, NOT designed to be disassembled and repaired. A long way from the 1940's-70's. 80's kind of a transition period.

Aww, loookeee I busted a knob offa my Blackstar. Such a simple thing, it's gonna take you just ten minutes to fix, can I pick it up tomorrow morning? Sure thing sonny.... NOT!

[Enzo]

Authorized service centers are like musicians: some are better than others.

It is like anything else, the first time I see one it may be inconvenient, like a Classic 30. But once I have seen it, it isn't a surprise. I can have a C30 all apart, boards out, in a matter of a few minutes.