SOLVED Too much voltage

[DAJE]

A couple of pedals made nasty noises and stopped working last night.

One of them (Aion Deimos, Tone Bender Mk2) did a weird thing where the LED would blink and the only sound through the amp was a ticking in time with the blinks.

The other is my Kliché Mini, which simply stopped working.

Currently they both do nothing. No sound, no LED, nada. The Deimos passes sound because it's truly bypassed, the Kliché isn't so it's a brick.

They were plugged into the same power supply, along with the rest of my pedals. Long story short, I suspected the supply might have an issue, so I tested the outputs with a battery tester and an adaptor. Most of the outputs put out a little over 9V, but one was 15V and two - I think the two that the affected pedals were plugged into - were over 20V.

So, yeah, the power block outputs are genuinely isolated, but 20V into my pedals is a very bad thing and I am very annoyed that I didn't think to test this before. There are DIP switches, but they were all set to 9V, and I switched them and retested and they still put out way too much voltage. It's a Mosky C8, a clone of a Voodoo Lab PP2+.

OK, thanks; I do not want or need a lecture about how I shouldn't have bought a relatively cheap power supply. If that's your only contribution, save yourself the effort. I bought it a while ago, didn't start using it until fairly recently, I have no chance of getting a refund, it's going into the e-waste pile, let's all move on with our lives now.

The rest of my pedals are fine.

I tried batteries and I tried a known good 9V power supply. No result.

I swapped out the charge pump in the Deimos with one from a working pedal: no change. The diodes look fine, no sign of them having blown up or burnt out. No magic smoke release that I can see or smell. Everything looks OK.

Deimos schematic attached.

Anyway, getting to the question - what should I check? And, given that I do not have an audio probe, and may or may not have the parts to build one, how do I check? I can check continuity with my MM, and voltages, beyond that I am unsure. Any informed guesses as to how much is likely to be in need of replacement?

EDIT: The electrolytics in the Deimos are all rated at 35V, the ones in the Kliché Mini are a mix of 35V and 50V. They all look fine, no sign of any damage that I can see.

 

[JamieJ]

That sucks! Can you add some pictures of the power supply parts of the board? Any resistors that look odd or different?

 

[music6000]

A couple of pedals made nasty noises and stopped working last night.

One of them (Aion Deimos, Tone Bender Mk2) did a weird thing where the LED would blink and the only sound through the amp was a ticking in time with the blinks.

The other is my Kliché Mini, which simply stopped working.

Currently they both do nothing. No sound, no LED, nada. The Deimos passes sound because it's truly bypassed, the Kliché isn't so it's a brick.

They were plugged into the same power supply, along with the rest of my pedals. Long story short, I suspected the supply might have an issue, so I tested the outputs with a battery tester and an adaptor. Most of the outputs put out a little over 9V, but one was 15V and two - I think the two that the affected pedals were plugged into - were over 20V.

So, yeah, the power block outputs are genuinely isolated, but 20V into my pedals is a very bad thing and I am very annoyed that I didn't think to test this before. There are DIP switches, but they were all set to 9V, and I switched them and retested and they still put out way too much voltage. It's a Mosky C8, a clone of a Voodoo Lab PP2+.

OK, thanks; I do not want or need a lecture about how I shouldn't have bought a relatively cheap power supply. If that's your only contribution, save yourself the effort. I bought it a while ago, didn't start using it until fairly recently, I have no chance of getting a refund, it's going into the e-waste pile, let's all move on with our lives now.

The rest of my pedals are fine.

I tried batteries and I tried a known good 9V power supply. No result.

I swapped out the charge pump in the Deimos with one from a working pedal: no change. The diodes look fine, no sign of them having blown up or burnt out. No magic smoke release that I can see or smell. Everything looks OK.

Deimos schematic attached.

Anyway, getting to the question - what should I check? And, given that I do not have an audio probe, and may or may not have the parts to build one, how do I check? I can check continuity with my MM, and voltages, beyond that I am unsure. Any informed guesses as to how much is likely to be in need of replacement?

EDIT: The electrolytics in the Deimos are all rated at 35V, the ones in the Kliché Mini are a mix of 35V and 50V. They all look fine, no sign of any damage that I can see.

Kliche will be D3 1N4742 Zener diode, 12V is blown.
Deimos will be Z1 1N4742 Zener diode, 12V is blown.
1N4742 is designed to do this to protect the Charge Pump!

 

[DAJE]

That sucks! Can you add some pictures of the power supply parts of the board? Any resistors that look odd or different?

Here's the Deimos - it's one of the first pedals I made, my soldering is better now. Nothing obviously broken.

 

[DAJE]

Kliche will be D3 1N4742 Zener diode, 12V is blown.
Deimos will be Z1 1N4742 Zener diode, 12V is blown.
1N4742 is designed to do this to protect the Charge Pump!

That's what I was thinking. They look OK, but I think you're right.

EDIT: Look what I found in my box of spares. I knew my habit of buying a few extras of things like this would pay off.

 

[music6000]

That's what I was thinking. They look OK, but I think you're right.

EDIT: Look what I found in my box of spares. I knew my habit of buying a few extras of things like this would pay off.

The 1N4742 is designed to blow if more than 12v is put through it, it's cheaper to replace than the Charge pump.
Cool, you have 2 spares or you did have 2 spares!

 

[Big Monk]

That's what I was thinking. They look OK, but I think you're right.

EDIT: Look what I found in my box of spares. I knew my habit of buying a few extras of things like this would pay off.

Have you tested the diodes yet to see if that's the issue?

The more interesting scenario here is how you are developing 20 vDC on taps of the supply. That's the part that piques my interest...

 

[thesmokingman]

keep in mind that power supplies will measure high with no load on them ... if it is an unregulated supply it can run high if the supply from the wall is high ... for instance if the power specs are at 110 or 115 VAC and your wall is 120 your mileage will vary towards the high side

 

[DAJE]

The 1N4742 is designed to blow if more than 12v is put through it, it's cheaper to replace than the Charge pump.
Cool, you have 2 spares or you did have 2 spares!

I just finished replacing the one in the Deimos, and it's now working again. I'll do the other pedal tomorrow. Thanks for your help on this. Much appreciated.

 

[DAJE]

keep in mind that power supplies will measure high with no load on them ... if it is an unregulated supply it can run high if the supply from the wall is high ... for instance if the power specs are at 110 or 115 VAC and your wall is 120 your mileage will vary towards the high side

I'm in Australia, we have 240V here, more or less. It's usually a bit less because we've standardised with the EU who standardised on 230V. The power supply has 8 outputs, and 5 of them put out just over 9V. I'm testing with a battery tester, but I've had accurate results with it compared to various other testing devices, so I trust it.

 

[DAJE]

Have you tested the diodes yet to see if that's the issue?

The more interesting scenario here is how you are developing 20 vDC on taps of the supply. That's the part that piques my interest...

Replacing the diode in the fuzz resulted in a working pedal, so that's the issue. Not sure what you're asking about the 20V - I tested with a battery tester that I trust to be accurate. If you're wondering how the power supply was putting out that much voltage - yeah, that's an interesting question. It has DIP switches to set for 12 or 18V, but they were all set to 9V for sure, and I flicked them up and down a few times and tested again, and they were still reading the same. So, I guess I discovered where they cut corners.

 

[music6000]

I'm in Australia, we have 240V here, more or less. It's usually a bit less because we've standardised with the EU who standardised on 230V. The power supply has 8 outputs, and 5 of them put out just over 9V. I'm testing with a battery tester, but I've had accurate results with it compared to various other testing devices, so I trust it.

Well there ya go, I'm in W.A (Western Australia) !

 

[DAJE]

Well there ya go, I'm in W.A (Western Australia) !

I'm in Melbourne, so you know how late I'm up. Sorry about the heatwave, it was bad enough here.

 

[Big Monk]

Replacing the diode in the fuzz resulted in a working pedal, so that's the issue.

Right, and I'm glad it worked out for you but my #1 rule is always to KNOW a component is bad before replacing it. In your case the Zener was the bad component but i was just trying to caution you against putting the iron to the thing until you knew for sure.

Not sure what you're asking about the 20V - I tested with a battery tester that I trust to be accurate.

Right. Wasn't questioning the reading just wondering what physically/electrical scenario would allow that.

If you're wondering how the power supply was putting out that much voltage - yeah, that's an interesting question. It has DIP switches to set for 12 or 18V, but they were all set to 9V for sure, and I flicked them up and down a few times and tested again, and they were still reading the same. So, I guess I discovered where they cut corners.

This was what I was driving at. The isolation is transformer based (IEC plug and 120/240 vAC nom) and then I'm sure they use individual regulation for the taps.

What's interesting is that only Tap 6 approaches 20 vDC in normal situations and in this case you'd need to the DIP switch set ON to get the 18 vDC it provides. Like @thesmokingman said, if you read them unloaded that could cause the voltage to creep up but even in that case, to have 20 vDC on anything but Tap 6 seems like you had a dead short from the input of the tap regulator to the output jack for the taps. And then the issue you describe with the DIP switches.

I'm glad you worked it out but there seems like a number of things that would have to have gone wrong that can't simply be explained by it being cheap chinese junk. I personally have a fondness for some cheap chinese power supplies.

This kind of stuff ends up being more interesting than the troubleshoot of the pedals!

 

[DAJE]

What's interesting is that only Tap 6 approaches 20 vDC in normal situations and in this case you'd need to the DIP switch set ON to get the 18 vDC it provides. Like @thesmokingman said, if you read them unloaded that could cause the voltage to creep up but even in that case, to have 20 vDC on anything but Tap 6 seems like you had a dead short from the input of the tap regulator to the output jack for the taps. And then the issue you describe with the DIP switches.

I'm glad you worked it out but there seems like a number of things that would have to have gone wrong that can't simply be explained by it being cheap chinese junk. I personally have a fondness for some cheap chinese power supplies.

This kind of stuff ends up being more interesting than the troubleshoot of the pedals!

I'll open it up and take some pics for you tomorrow, if you're interested. I'd happily donate it to you but it's surprisingly heavy and postage would be way too expensive.

 

[DAJE]

Some gutshots. Interesting mix of SMD and through-hole e-caps. Those big green e-caps are 1000μF 25v. Kind of want to harvest them for the cool factor but I don't think there's much call for them in pedal circuits.

@Big Monk - I can probably take the PCB out if you want a closer look at anything.

 

[DAJE]

Also, I replaced the Zener in the Kliché Mini, and it's now working normally again. Yay!

 

[music6000]

I just finished replacing the one in the Deimos, and it's now working again. I'll do the other pedal tomorrow. Thanks for your help on this. Much appreciated.

Did the Kliche Mini turn out OK?

 

[DAJE]

Did the Kliche Mini turn out OK?

Yes, replaced the Zener and it's A-OK. Thanks again.

 

[Iceman53]

Some gutshots. Interesting mix of SMD and through-hole e-caps. Those big green e-caps are 1000μF 25v. Kind of want to harvest them for the cool factor but I don't think there's much call for them in pedal circuits.

@Big Monk - I can probably take the PCB out if you want a closer look at anything.

FWIW - The gut shots of your PS look relatively similar to my Voodoo Labs 4x4 PS, which I recently repaired. One of the 12 volt regulators was putting out 23 volts. The regulator (LD1117) ended up being bad. Mouser had them for $1.20. Might be worth giving that a shot if you want to try to repair your supply. Hope this helps.