Dirtbag Deluxe Level control problem + burned Cap

[WLTerry]

Hey guys, 1st time I'm posting here. I've build two Dirtbgs, one w/one Smallbear's Fake 3005's pair and the 2nd with two pairs of those Fake 3005's, in order to get one pedal with shorter delay time and the other with longer delay time. Those projects are amazing and the boards are exelent.

My second Dirtbag have 2 pairs or fake 3005's. I built it like two weeks ago and was everythng working OK, but yesterday afternoon while I was fooling around with my guitar, suddenly I heard a huge noise with the delay engaged on. I opened it and I found that cap C46 was burned out whit lots of fume and this nasty smell.

According with the schemaic, this cap is only for the power supply section, I grab my multimeter and found there's a short-circuit between 15V and GND. Nothing inside the box could make it short-circuited, because there are duct tape covered inside. I take off the cap and still was short-circuited... then I cut the 15V track coming to the positive pad and there's no more short circuit.

BUT... the issue is this: The Level control started to fail. Usualy you can get the unity gain with the Level pot at noon. Now I barely can approach it at full clockwise, still it sounds a bit lower than normal. I swaped the IC1 for a new TL072, checked resistors and caps around IC1 and everything seems normal.

Is there someting I missing in my debug? Maybe switching the R3 resistor I can adjusgt the gain? But the ideal scenario is that I could find the error.

Thanks so much in advance
Will

[madbean]

Will, welcome to the forum.

Sorry to hear about the Dirtbag. Can you give us some voltages on IC1?

[WLTerry]

Hey Bean, thanks.

I'm currently in the office, but I barely remember the voltages I measured yesterday. There was 14.9v in pin 8, 0v in pin 4 and the other poins have like 5,6v I think. I compared with my other dirtbag and seems to be the same volts. Once I get home I'm going to meassure the voltages again and I'll post the results.

thanks

EDIT: The pedal works everything fine, the delay and modulation. Only the Level control have problems.

[WLTerry]

Yep, voltages in IC1 are pretty much the same I posted hours ago, 14.84v in pin 8, 0v in pin 4 and the other pins are 5.76v.

I also measured the R2 and R3 resistors and the level pot an seems to be OK. I can't measure C1 and C2, but they looks ok.

I'll try to debug the thing some more, so you guys have any any idea of what I can do?

Thanx
Will

EDIT: Is that supose that VB (pin 3) sbould be like 7v or so, because of the voltage divider from R59 and R60?

[WLTerry]

So, this is really weird. The pedal is working now like a charm.

What I did is take off R4 and C3 in order to isolate IC1A and continue to debug. The original gain properties came back... loud at full clockwise and close to unity gain at noon. Then I soldered back C3 and R4 and voilá.... the pedal is working again like normal.

Now I put the pedals in my rack drawer and I can confirm is working good along with my other pedals (mostly DIY). I wanna say thanks to Madbean for those amazing boards and to all the people who's sharing their their experiences in this DIY adiction.

See ya soon
Will