zombii smoke

[eniacmike]

I built my zombii up and it tested great. I made two subs 5kc for stab and 5kc for volume.

I got my enclosure drilled which took two times. the first time there wasn't enough room for the battery. I think my drill walked up on the stomp switch. ALSO the drilling template on the project files has the led in the wrong place, it should be on the right between drive and stab.

Anyways I had my pedal all wired up and ready to test and it was sounding really weak then I saw smoke coming off the circuit! I shut it down and tried to figure out what was wrong.

I am still not sure what went wrong but I think something is wrong with my stability pot. I could get the circuit to work if I twisted the pot all the way to the left. The circuit also works if I short lug 1 and 2 or lug 2 and 3 out.

I am not sure why my circuit smoked but I am guessing the pots might be damaged. I just ordered new pots to try to replace them all. Is there anything else I need to check.




the soldering on the bottom right (the power section) looks worse than it is. I just did alot of rework there trying to fix the problem, there are no shorts.

[jkokura]

Since your caps look like they're fine in your picture, I think the smoke could be three things: one or more of the Trannies are blown, one or more of the pots are blown, or you had some sort of residue on the board that burned off when powered up.

If it's not any of those things, I don't know what you can do. I imagine if that stab pot isn't working right that replacing the pot might help. Bad pots are known to happen...

jacob

[eniacmike]

thanks,

I am almost positive it is the stab pot because when I short out 1-2 or 2-3 it works and sounds fine.

I just removed the pot and tested it and usually when I test a pot and turn it full cold 1-2 sound the continuity alarm, then if I turn it full hot 2-3 will sound the continuity alarm. It still measures 5.7K across from 1-3 but something isn't working right inside the pot.

I ordered replacement pots from mouser already so hopefully they come saturday and I can check it out.

[eniacmike]

I put the replacement pots in and it worked perfectly for about an hour but when I was adjusting the stability pot my pedal stopped working again, and it appears the stab pot is broken again... surely something is wrong with my circuit somewhere? it doesn't explain why the stab pots keep failing?

[madbean]

I think you've got some kind of short having to do with your battery or DC jack. If using a battery: does it get really hot after a couple of minutes?

[eniacmike]

I think that my battery case might be shorting 9v to ground? the case is touching the bottom of the pcb. that is probably it. I will have to replace the pot again and see..

[jkokura]

Try seeing if the battery gets hot. I'm surprised that you have a pot burn out instead of having the diode burn out first. The Diode is there to protect the circuit incase the power switches direction...

Jacob

[oldhousescott]

I'm guessing it was your Stab pot that smoked. Check that the wiper of the pot isn't shorted to ground. If it is, as you turn it more clockwise, you'll be putting 9v to ground directly across a small portion of the pot track. Poof.

[madbean]

I've actually discovered a mistake in the schematic. C1 needs to be reversed (the 10uF input cap). The negative side needs to go towards the input, and the current schem shows it the other way around. I don't know if this is causing your problem (I think in this circuit the polarity of the input cap should not matter), but I would go ahead and fix that.

I found this mistake by accident: I built up the prototype for the next version today and was getting output, but no fuzz. As I went over everything and compared it to some other schems I found my mistake. Turns out my problem was actually my trannies, but I did swap out the cap and trannies and now it works perfectly.

[maysink]

So you gotta be wearing the right cap to get your trannys to put out, eh? 

[madbean]

Well, I'm pretty sure the cap can swing either way in this case, but I would switch it around to make sure you get the good tranny fuzz.