Muzzle not working (multiple problems)

[entropia]

Hi!

I built a muzzle kit. I got it working briefly, but when putting the covers on I guess a contact error happened somewhere and some component touched the case. There was a little bit of some smoke coming out when I opened the case. This got me worried.

- No visible burn marks inside and all the components look normal to naked eye
- The audio passes through the key in & out
- The audio passes through in & out when the pedal is bypassed
- The light does not respond, it stays in one color
- Components Q1-Q4 become very hot when the power is connected

Any tips from where to start looking or what possible could be wrong?

 

[fig]

Hi,

The last I read, you had a high-pitched squeal and were making/considering mods to the circuit. Can you post some current pictures and describe any mods to the circuit? Something is obviously making ground that should not.

 

[entropia]

Hi,

The last I read, you had a high-pitched squeal and were making/considering mods to the circuit. Can you post some current pictures and describe any mods to the circuit? Something is obviously making ground that should not.

I didn't get that one working and I think it is beyond saving. This one is a totally new kit I built today (I had two). I built it standard without any mods. I can post pictures tomorrow but I followed the instruction very carefully.

 

[Feral Feline]

Did your first build also release the magic smoke?

 

[entropia]

Did your first build also release the magic smoke?

No.

 

[Feral Feline]

Well, thats good. Maybe it can be salvaged after all.

If it had, then it might’ve been easier to track down the present build’s problem.

If you smoked something, then possibly a polarised cap or other component was inserted backwards — the damage may be between the component and the board, so not visible.

The Qs heating up is disconcerting…

Looking forward to pics, and then hopefully someone can solve the mystery.

 

[entropia]

Well, thats good. Maybe it can be salvaged after all.

If it had, then it might’ve been easier to track down the present build’s problem.

If you smoked something, then possibly a polarised cap or other component was inserted backwards — the damage may be between the component and the board, so not visible.

The Qs heating up is disconcerting…

Looking forward to pics, and then hopefully someone can solve the mystery.

If something was the wrong way, I think the build wouldn't have worked at all? Now it worked for a while.

 

[Feral Feline]

That’s not necessarily the case, sometimes a circuit can still work improperly with a reversed component — at least until that component is re-oriented properly to make the circuit sound as it should, or until it burns up from having to continue to work incorrectly. Depends on the circuit, the part and its role within the circuit.

For example: JFETs generally work when reversed; some circuits spec a reversed BJT to force it to work incorrectly and thus get a crazy sound — but that’s not the case here.

 

[entropia]

Here's some pics. Indeed, the pedal worked normally for a short while. It had some contact errors and while figuring them out there was smoke. Upon further inspection apparently only Q1 & Q2 heat up, other side stays normal.

 

[entropia]

Any tips or clues?

 

[Robert]

Check the voltage on the collector of Q1.

Q2 could get warm if there is a problem elsewhere in the circuit but Q1 shouldn't have a path to ground with low enough impedance to cause anything to get warm.

Make sure Q1 - Q4 are all 2N3904 as well, while you're at it.

 

[entropia]

Check the voltage on the collector of Q1.

Q2 could get warm if there is a problem elsewhere in the circuit but Q1 shouldn't have a path to ground with low enough impedance to cause anything to get warm.

Make sure Q1 - Q4 are all 2N3904 as well, while you're at it.

It's been awhile, not have had time to investigate. How should I check the voltage and what should it say? I checked the parts, they all match and are correct. Q2 gets the most heat and it heats up instantly when I power on.

 

[JulDP]

Hi,

I would like to chip in here. I also just built the same Muzzle. It is gating. The key and passthrough are working properly. However, while testing it I found that there is a squeal around 14 kHz when no cable is connected to the input jack. This comes both through the output and the Passthrough. When connected, the 14 kHz is still there, but unaudible. I add some pictures of the tests with Threshold at zero. (1. Pedal off, 2. Pedal On, 3. No Cable in the input Jack). Could it be first OpAmp stage? I think that I will test it with another TL072 later. Any ideas welcome.

cheers

Update:

I changed the TL072 but the problem persists. And I was also wrong, with a cable connected to the input the squeal is still there. I tried it with some distortion pedals and when I turn up the gain, at some point the squeal jumps put at you. The Muzzle is gating, it could silence the squeal for sure but of course as soon as I play something... bleeding ears. I´ll keep looking for the problem.

 

[entropia]

Any ideas?