Clarinot gettin' hot!

[jonnygreentrees]

Just finished a Clarinot clone on a pcb, plugged it in to test it and there's no sound coming out and all the components on the pcb are getting really hot!

Going to troubleshoot tomorrow but am I right in thinking this is almost certainly a short circuit issue?

[GibsonGM]

That's most likely the problem, Johnny.  Hope nothing got burned due to it!       

Don't apply power again, lol....if you have a meter, look for continuity between your power wires...read the resistance between them, and post back here....often this happens because of an accidental blob of solder getting between the + and -  (a 'solder bridge').   We'll help you troubleshoot it.

[duck_arse]

the thing about a short circuit is that it shorts the circuit. the current doesn't get to reach all those places other beers can't, so the circuit doesn't work, and only those parts passing the current, ie those in series with the short, would be getting hot. so, if it's a short, only a few hot parts; if it's reversed supply, maybe everything/maybe only some things are getting jazzed up the jaxy, and producing the unwanted heat.

check everything you thought you'd wired right again.

[jonnygreentrees]

thanks all will check all that out. Although I socketed it my PT2399 was getting hot too, hope I haven't fried it!

[GibsonGM]

Absolutely, Duck, just keyed on what he said about 'parts getting hot'. So, his short is likely beyond the power connections, maybe across the chip, etc...it's a tough break, but we've all done it!!  Might make it if you can find it and correct it...usually this is done by looking at EACH connection with a magnifying glass, believe it or not.  If the chip is socketed, carefully remove it before you get in there with a soldering iron again! 

[jonnygreentrees]

OK firstly go easy on me as this is my first build on a DIY pcb and also where I have sourced my own parts rather than built from a kit!

Anyway I have just checked all my off board connections and everything seems ok also have checked for solder bridges with a DMM and I can't find any. Basically I'm getting no sound and the 78L05 is getting super hot to the touch within a minute of connecting power. Any ideas where I should check first and what I should be checking for?

[jonnygreentrees]

and here's a link to the schematic

http://music.codydeschenes.com/wp-content/uploads/2012/12/MidFi-Clarinot-MB-DoomButter-v2-TRANSFER.pdf

[jonnygreentrees]

Pcb before population

[jonnygreentrees]

Handy side by side which shows that in the few areas where there are bridges those parts connect anyway

[Cozybuilder]

If I'm looking at the PCB correctly, I think the regulator is backwards- it looks like the 9V in goes through the 1N4001 diode, then should go to the regulator input. The pinout for an LM78L05 is out-gnd-in, with flat towards you and leads down.

[jonnygreentrees]

thanks I checked this and it's definitely in correctly

[Cozybuilder]

If you are referencing the component layout of the Doombutter, the LM78L05 regulator (TO-92 package) is drawn in backwards. It would be correct for the LM7805 (TO-220 package)

http://music.codydeschenes.com/wp-content/uploads/2012/12/MidFi-Clarinot-MB-DoomButter-v2-TRANSFER.pdf

Compare the tracing to the schematic- the 9V lead goes to the 1N4001 Anode, the cathode is connected to the input of the regulator, and also is routed to Pin 6 of the 386, and the positive lead of C9 to ground.

[jonnygreentrees]

ah ok so as mine is the TO-92 I need to orientate it the opposite way round to how I have it at the moment?

[Cozybuilder]

Yep

[jonnygreentrees]

damn just tried that and still no dice!

The power is definitely getting in as the regulator is getting hot so working my way forwards from 9v in the diode is getting a forward voltage of 0.514v. I assume this is ok?

[Cozybuilder]

Do you have a fresh 78L05 to try? If not, remove the chips and verify the voltages at pin 1 of the PT2399, and pin 6 of the 386. The diode should drop about 0.6V. You're looking for 5V and about 8.5V.

[jonnygreentrees]

thanks for all the help! Do you mean remove the chips from the sockets and with the circuit powered on test the voltages on those pins of the sockets?

[Cozybuilder]

Yes. Now its a matter of figuring out if the reg is fried, or if the problem extends to any circuit components. By removing the chips (I see they're socketed) you can at least determine if the reg is OK with the voltage test. I suspect it will be toast. But if its OK, then its going to take a bit more effort to determine what is wrong- my guess would start with the PT2399, but first things first.

[jonnygreentrees]

OK so embarrassingly I have realised that the guitar lead that I was using between pedal and amp was broken! Have tried a new lead and am now getting very distorted noise out of the pedal and the knobs are affecting the sound, however the reg is still getting mega hot. I have ordered new ICs and a new reg, is it possible I have fried them?

Also the PSU I am testing the pedal with is 500mA output, is this too high?

[Kipper4]

The wall wart should be fine the circuit will only pull the currant it wants.

Have you checked the voltage at the reg out? As Russ says remove the chips first.