Ruined Pedal STILL Not Working after Repair?

[Slight Return]

Hey all.

I stupidly let my friend talk me into trying some random 9v adapter to power a wah pedal I put together, and it ruined the pedal. Ended up being an AC adapter or something like that. Great.

I had a spare board. I just replaced the ENTIRE circuit board with the new board, and the pedal makes no sound at all when on. The ONLY component I transferred from the old board to the new board is the inductor that I hand wound and assembled myself. I tested it in and out of the circuit and it's getting the exact inductance and resistance readings it should be getting.

Are there other components, such as the switch or the 9v power adapter, that can be damaged from plugging into the wrong power supply?

I'm racking my brain over here that the pedal still doesn't work despite replacing the entire circuit board.

Thanks! Also a lesson to me to never listen to other people when my instincts tell me otherwise. I knew better. Oh well.

[Slowpoke101]

Depending upon how much current was going through the effect during the fault other things can get damaged due to heating.
Check the 9V DC connector. Sometimes they melt or partially melt and no longer work correctly.

Also just make sure that you do have all the board wiring hooked up correctly.

[aron]

Please make sure the wah is getting power on the board where it should have. The audio probe is also great for debugging this sort of thing.
https://aronnelson.com/diywiki/index.php/Debugging

[Slight Return]

Is it possible for the switch to have been damaged?

I triple checked the wiring and everything checks out. I tried a different 9v adapter, but now I'm worried that since it didn't mark the polarity on the adapter, I may have hooked it up in reverse and damaged the new board as well, while trying to test for voltage.

Is that possible? How are you supposed to know what polarity a female barrel jack adapter is when there are no markings indicating polarity? I left the "insertion detection" lug empty and hooked up the hot and ground leads to the tip and sleeve lugs on the female barrel jack.

Anyway, I am getting 9v when everything's plugged in. Disconnected the DC power jack and hooked up a battery to test just to make sure, since I'm unsure of the power jack's polarity.

Originally, I removed the 5 wires attaching the board to the jacks/switch, and replaced them onto the new board. I am 100% positive I wired it correctly, and the board is pre-assembled.

Which is why I assumed something else blew out, if that's possible: the DC adapter or the switch. But now I fear that in attempting to replace the power jack, I may have inadvertently hooked up the wires in reverse and damaged the new board as well.

If there's any way to know what the polarity is on a female barrel jack, or how to avoid this mistake in the future, I'd love to know.

ALSO: If I turn the amp up a LOT, I am getting SLIGHT signal when the pedal is on. However, there is no wah effect, even at such a low volume (maybe 5% of total volume, or what the volume should be).

Before I tinkered with the DC jack, everything was just transplanted: brand new board in place of the old board. The DC jack does not appear to be visibly damaged in any way whatsoever.

[DIY Bass]

What about the pot?  Was that part of what you replaced or did you use the original one?  Easy to measure it with a multimeter.  Also, There is a possibility that some of the new wiring may inadvertently short to the case.  I have done that a few times, and even come across commercial pedals with shorts to the case.  Your board should have reverse polarity protection diode in place to prevent damage from reverse polarity.  If it doesn't then it might be a good idea to add one in to the wiring from the power jack.

[EBK]

Originally, I removed the 5 wires attaching the board to the jacks/switch, and replaced them onto the new board. I am 100% positive I wired it correctly, and the board is pre-assembled.

Is that 100% positive because you repeatedly checked that part, or 100% positive because your confidence told you that you could skip checking that part?

[Slight Return]

I checked against the diagram multiple times. The boards are identical, and I desoldered one wire at a time from the old board, and re-soldered it to the corresponding section on the other board. While I was doing this, I double and triple checked each connection against the diagram to make sure it was in the correct location.

There are only 5 wires going to the board, all different colors, and I checked every single one against the diagram at least 3 or 4 times during the installation, and then another 3 or 4 times after installation, and just went back and checked it against the diagram again and verified that every wire is going exactly where it was going originally according to the wiring diagram.

[EBK]

Very good.  Just being thorough.  Not trying to imply anything about your judgment. 

[Slight Return]

No offense taken. It's very, very easy to miss a connection point and it's a good to be reminded to check, and check again. Sometimes it's that simple. Checked again after you posted just to make sure. Especially after looking at a circuit for so long, it can be easy to miss a mistake.

[Slight Return]

What about the pot?  Was that part of what you replaced or did you use the original one?  Easy to measure it with a multimeter.  Also, There is a possibility that some of the new wiring may inadvertently short to the case.  I have done that a few times, and even come across commercial pedals with shorts to the case.  Your board should have reverse polarity protection diode in place to prevent damage from reverse polarity.  If it doesn't then it might be a good idea to add one in to the wiring from the power jack.

I didn't check the pot. I didn't think that could get damaged.

I set the meter to 200k Ohms, and tested the pot. It does seem to be going between 95k and 0k when moving the wah up and down. That's with the probes on the center lug and ground lug.

[thermionix]

I doubt the pot or switch would have been damaged.  Can you share the schematic you followed?  Is there a reverse power protection diode?

[Slight Return]

No power or polarity protection diode. The board I used was from eBay, with a hand drawn wiring diagram. Carbon copy of a vintage Clyde McCoy. It's here:

https://www.ebay.com/itm/Vox-Wah-Crybaby-Wah-PCB-Boards/253974325400?hash=item3b220ca898:g:a1cAAOSw9E5b5vFV:rk:5:pf:0

Everything is pre-assembled, the only wiring is the 5 wires that you solder to the terminals on top of the board that go to the jacks/pot/switch.

Everything was fine until plugging in the wrong power supply. I just find it very strange that replacing the board didn't solve the problem. I even replaced the switch today and that didn't do anything either. Still absolutely no signal when turning the wah on, everything just goes dead. I made triple sure that no grounds were touching anything anywhere.

So the wah is ruined. One more question: is the PCB okay, and if I replace every single component should everything work again?

I wound and assembled the halo inductor myself, and after testing it with my LCR meter, it seems perfectly fine. I can probably source the other components with enough effort. Would it be possible to simply remove every component and use the PCB to start from scratch, and build a proper board using protection diodes and all that?

It was a fantastic sounding wah and the inductor I made for it sounded absolutely phenomenal. I would love to get this thing working again and if that means replacing every component that's what I'll do. I'm not sure if it's possible for the PCB itself to have been damaged though. There is no visible blackening or damage on the PCB that I can see.

[GibsonGM]

Dude, did you audio probe the circuit to see where signal dies, or if it's even getting to the board??

There are so many things you could do other than repopulating the board, but kind of hard to describe in a paragraph, such as transistor testing and the like.   It's an experience thing.     If you can lay hands on a schematic, you can track down the signal path w/audio probe.  If not, you can find the input and follow it, if you know something about how the signal should go (most wahs aren't that complex).

You can find every point on the PCB and offboard stuff that needs to be grounded and check that (jacks too).   

SOMEWHERE the signal enters the board (or not!), and somewhere it dies...I've found it's switch, much of the time, possibly ruining it by overheating during desolder/solder...heck you can even tack jacks to a raw PCB to see if it's living or dead (I do this with every build before the switch gets wired in).   Somewhere there is an error, or a dead part (if it worked before, probably error!).  Hey, maybe it's running fine right up to a missing solder joint on the output cap, or it popped off the PCB or something!?   No way to say without audio probing.

Yes, you could re-use the PCB, unless there's a ruined trace you can't see.  But that's a lot of work, when you might be able to solve this with less.  I'm for audio probing the thing, it will help you do the next one faster.  As in, don't give up, man!! 

[ElectricDruid]

+1 agree with Gibson. Don't give up on it.

Although it seems difficult to imagine if you're getting nothing out of it right now, I don't see why the whole board would be dead, *even if you had done something daft* to the new board. Perhaps you damaged one or two bits, but the whole thing dead? Just doesn't happen in my experience. Bar lightning strikes, maybe.

So let's back up and treat this like a clean build. You've just put together a wah pedal and it isn't giving you any sound - there must be a thousand threads like that one here, and a lot of them have positive outcomes.

Can you audio probe it to see if you've got sound to the board? What voltages have you got around the PCB?

[R.G.]

E.D. is correct. There is no mystery here, only facts that you have not discovered. I have myself experienced the adrenaline rush of "OHMYGOD!! I just killed my new [insert thingie killed here]!" This can be so bad that it stops you - it did me... - from thinking in a clear way.

First: it's unlikely that the PCB was damaged. Second, it's very unlikely that the resistors are damaged, or your inductor. Electrolytic caps might have been damaged, as may the transistors. So the thing to do, as E.D. says, is to treat it as a new build that is giving you no sound.

And that falls back to the advice given in the stickie thread that you have to skip over to look at all the rest of the posts here. It's titled "Debugging - what do do when it doesn't work".

Get out your voltmeter. Hook up power, and measure the DC voltages from ground to the input wire, output wire, and all three terminals of both transistors. This is very likely to point to a problem, if the problem. It is also likely to show up a broken or mis-wired power or ground wire. Once you verify by measuring voltages that the board is in fact being powered correctly, then you can start using an audio probe to see what's happening with signal.

Do you actually know the schematic that exists on the actual board?

[brianq]

I would double & triple check to confirm the wiring is correct, then audio probe the circuit. If you can get a schematic, it would help you follow the path of the circuit. Wha's are pretty simple, it shouldn't be this hard to get it working? Trust the probe, it don't lie?