Blue Magic not working

[cmat]

I just built a blue magic and I am not getting any sound and there is a spark comeing from lug 2 and 1 on the drive pot.  I dont want to turn it back on until I think I have the problem fixed.  I have checked all of the wireing and the polarity of the caps also I checked for solder traces everthing looks fine.  I would appreciate any ideas.  Thanks

[cmat]

BUMP

[Fret Wire]

It will be easier to help you out if you organize all the info on your build according to this format. It speeds up the debugging process. Btw, sparks are bad: double check your wiring and polarity.
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[cmat]

I have triple checked everything.  All of the wiring is correct and the polarity of the caps are correct.  I built it on a board from GGG and followed the directions.  The only thing I substituted was the 30pF cap for a 47pF.  The spark happen when I turn the pot past 80% but I have no sound but there is a pop when I turn it on.  I dont want to turn it back on for fear of doing any damage (I am hopeing it is not damaged).  Would there be a current like that going to the pot?  Could the pot be shorting out?  A bad pot?  Not being able to turn it on makes figuring out the problem very hard.  I have never experienced a problem like this.  Usually if I have a project that doesnt work it is a bonehead move like wiring a pot backwards or leaving an IC out (I have done that )  All help and any ideas are greatly appreciated because I am stumped

[petemoore]

  You can check the variable resistance of the pot with a DMM, on Resistance range just above the pot, while slowly turning the pot, looking for dead spots [where the meter jumps to 0 in the middle of the pot range].
  Clip or hold one lead to the wiper, then check each side from there.
  Or just see if sound passes through, volume pot you could plug in and turn on the amp, touching the input, output, and ground lug of the pot to see if buzz goes through, the pot must be adjusted 'up' most of the way maybe.

[George Giblet]

To have a spark in that region you must have some screwed-up wiring.

Are you sure you have the pot lugs soldered to the correct position on the PCB?  Look at the layout pick and make sure the tracks on the PCB look the same as your PCB.  For example the +ve from the DC jack goes to the track with the jumper.  I'm thinking your drive pot is wired off by one termimal on the PCB.  Following the GGG pic, make sure you drilled out the left most hole, the one that goes to the ring of the input socket.

[cmat]

I noticed that the hole wasnt there like it was in the parts layout while I was building it.  I just ran the wire from the adapter jack to the ring with the other ground instead of drilling another hole in the board.  The pos going to the adpter jack is lined up with the jumper.  I originally thought this is where the problem was but it all looks good.  If it is wired up right (which I am pretty sure it is) would there be that much voltage going to that pot?

[George Giblet]

> would there be that much voltage going to that pot

That pot should have no DC voltage on it whatsoever.

There's must be a wiring error or a short, or faulty cap.  To get a spark I doubt it's a faulty cap - I'm thinkin the +ve rail on the PCB is shorting to something around the drive pot

If you have a multimeter you can measure some voltages around the pot, you can also use the continuity buzzer to check if the +ve rail is shorting to anything.

It is possible your board didn't etch properly and there's a minute layer of copper on the board causing shorts.  This type of thing can wreak havoc all over the board.  Buzzing with the multimeter can help.  To fix it you have to scribe around the tracks or use some abrasive material like sand paper to (carefully) clean it up ; you should wipe the board down afterwards.

[cmat]

WHY DIDNT I THINK OF THAT!!!!   That was it there was a copper piece between lug 2 and and R5 on the board.  Many thanks guys!!