Anyone know why my Sunking II board keeps blowin' up?

[upthepunxxx]

Sorry I think I said the charge pump was ic1, but I was just looking at the schematic again and it's ic3. Got off too late tonight to check anything, hopefully tomorrow proves more fruitful...

I'd take Bean's suggestion and jumper it.

[upthepunxxx]

Hey homies! I Jumpered r 32 and checked my voltage regulator socket voltages and everything checked out. I checked out ic1 and 2 with the regulator in and those checked out. I added everything back with r32 still jumped. I got signal this time but for some reason the gain pot doesn't do anything. The volume pot works but never fully turns the volume all the way off. Gonna do some prodding tonight and investigate further. Ill keep you posted. Again thanks for the help thus far! I love me some troubleshooting!

[mgwhit]

If your volume pot works, but never quite kills the signal, its lug 1 isn't properly grounded.  Test for continuity to ground.  Bad joint maybe?

Now that you can keep it running without the resistor burning up, post all voltages for all three ICs.  There's probably something still pulling too much current, so I wouldn't let it run for long.  The fact that your Gain pot isn't working may suggest a bad joint somewhere in that feedback loop, but there also might be something wrong in your VB voltage divider (R29, R30, C21).

[upthepunxxx]

Awesome! Thanks so much man. I did a ground test last night to make sure everything that wasn't suppose to be going to ground was not going to ground. Also maybe I should re hit the lug 1 pot. I was using that as my ground point when taking voltages and it seemed fine. But after hearing you say that I will double check it and re check voltages again. What exactly was r32 doing? Was it controlling the voltage before the transistor? Like is it bad that I am running the circuit to test things out without that resistor not there? My thinking being that it was burning up for a reason? Anyways I will check out the pot lugs tonight as well voltages and test for ground again. And also see whats up in the voltage divider section of the circuit. Thanks so much for helping me out! If you are ever in LA Ill buy you a beer or something.

If your volume pot works, but never quite kills the signal, its lug 1 isn't properly grounded.  Test for continuity to ground.  Bad joint maybe?

If your volume pot works, but never quite kills the signal, its lug 1 isn't properly grounded.  Test for continuity to ground.  Bad joint maybe?

Now that you can keep it running without the resistor burning up, post all voltages for all three ICs.  There's probably something still pulling too much current, so I wouldn't let it run for long.  The fact that your Gain pot isn't working may suggest a bad joint somewhere in that feedback loop, but there also might be something wrong in your VB voltage divider (R29, R30, C21).

[upthepunxxx]

One more thing. Its cool to just run the FAT mod right? I jumpered the THICK mod, exactly how I would if I was building a stock version (jumper wire from pads 1-2), but wired up a switch to the FAT mod and soldered capacitors for c6 & c8. Should I have omitted c6 since I am not using the THICK mod? Could that have Anything to do with my current troubles? Or at least why the gain pot isn't working? Maybe even screw with IC1B voltages?

[mgwhit]

The Fat Mod and the Thick Mod are completely independent.  Assuming you jumpered the Thick Mod off (correctly), you could safely omit C6.  And given that those mods are built onto the board, I don't think there's any way they could be messing up your voltages.

Here's one last thing I can think of to test tonight.  Try continuity between lug 2 of your Gain pot and the positive leg of C21 (leg of R29 right across from it).  Really try to get the tip of the pot lug rather than the PCB pad because we want to test the quality of the solder joint.

[upthepunxxx]

So I went back through to check all components. Surprise surprise! I Found a mistake. I put a 390nf cap instead of 390pf in c9. I can see how that would upset ic1s voltages, but is that the reason r32 was burning up? Gonna change out the cap and put a resistor back in r32 and see what happens. Wish me luck!

The Fat Mod and the Thick Mod are completely independent.  Assuming you jumpered the Thick Mod off (correctly), you could safely omit C6.  And given that those mods are built onto the board, I don't think there's any way they could be messing up your voltages.

Here's one last thing I can think of to test tonight.  Try continuity between lug 2 of your Gain pot and the positive leg of C21 (leg of R29 right across from it).  Really try to get the tip of the pot lug rather than the PCB pad because we want to test the quality of the solder joint.

[mgwhit]

I doubt that bad value in C9 is what is causing your voltage/current issues.  It would certainly make your pedal sound terrible, though. 

I can't believe we haven't suggested this before, but why don't you measure the current your board is drawing before you put that 10R resistor back in?  Probably won't help us debug anything, but at least we'll know the extent of the problem.

[Scruffie]

The reason I said pull the zener earlier is that when they go bad (and they can easily) they will draw as much current as they damn well please, directly following the 10R? Likely candidate.

I thought Bean had ditched it for over voltage protection, I remember it being the issue on previous Sunking boards.

[mgwhit]

The reason I said pull the zener earlier is that when they go bad (and they can easily) they will draw as much current as they damn well please, directly following the 10R? Likely candidate.

Thanks for the clarification!  I couldn't figure out why a functional zener would cause a current problem.  I get it now.

What would happen to a malfunctioning zener once you jumpered the burned out resistor?  Wouldn't it burn out?

I'd still like to see a current measurement, though.  I tend to forget that I even have that on my multimeter since I use it so infrequently.

[upthepunxxx]

I'm trying to think the best way to measure the current in its current state? Since I have r32 out right now, can I just run my multimeter right into those pads? So it's in the circuit? Or is that the complete wrong way? I guess I could wire up the batter snap and measure it that way right? Thanks again for all your help man, I've Learned so much more in this whole debugging process than I have in the last year!

Thanks for the clarification!  I couldn't figure out why a functional zener would cause a current problem.  I get it now.

What would happen to a malfunctioning zener once you jumpered the burned out resistor?  Wouldn't it burn out?

I'd still like to see a current measurement, though.  I tend to forget that I even have that on my multimeter since I use it so infrequently.

[mgwhit]

As long as you can make good contact to the pads, that should be the perfect place to measure it.  Be sure to start with your highest setting and the appropriate lead and work your way downward.

Based on what Scruffie said, I'd make sure that zener is removed from the circuit. If you get a reading that isn't high enough to blow that 10R resistor, then we can assume the zener was the problem.

Edit: Also remember to immediately return your multimeter to read voltage when you're finished.  If you try to read voltage using a ground reference with your multimeter set to current, you'll blow the fuse.

[upthepunxxx]

Rad! Thanks man, I'm gonna try it when I get home from bowling league tonight. I think I have bigger problems though. Possibly issues with my grounding. I had ordered another couple boards to see if I could build one that works and test it against the bad one. I built it the exact same way I built the other one. Meaning jumpered the thick mod and wired up the fat mod. This time I omitted c6 though. Fired it up and everything looked good. However I lowered the volume pot all the way and still got signal. So I'm guessing it's not grounding properly. Then I lowered the gain pot and when it's almost all the way off I get this weird octave up sound but pretty quiet. But the word thing is that everything else works completely fine. The volume tone and gain pots work fine except for when the pots are in those positions. I didn't get a chance to really see what else was going on as I had to leave. I also didn't check the fat mod switch now that I think about it. The frustrating this is that in the past couple months I've built 2 of the stock versions for a buddy I jam with,  and they work great! Long story short, I'm messing something up big time and I need to figure it out. STAT!

As long as you can make good contact to the pads, that should be the perfect place to measure it.  Be sure to start with your highest setting and the appropriate lead and work your way downward.

Based on what Scruffie said, I'd make sure that zener is removed from the circuit. If you get a reading that isn't high enough to blow that 10R resistor, then we can assume the zener was the problem.

Edit: Also remember to immediately return your multimeter to read voltage when you're finished.  If you try to read voltage using a ground reference with your multimeter set to current, you'll blow the fuse.

[upthepunxxx]

So I measured some voltages as well as current draw last night. I attached the IC voltages as a text document. I think everything looks pretty standard...?

Current Draw for the board that was blowing up r32 is:
6.6ma read from R32 (10ohm 1/2 watt resistor in) with everything in circuit except IC1
8.4ma read from R32 (10ohm 1/2 watt resistor in) with everything

I didn't really remove IC1 for a particular reason. I was measuring current draw then realized I had it out. Since it was a different current draw, I figured I would include the reading.

Trying to figure out my next move...

[mgwhit]

Yeah.  Wow.  Did you already remove the zener?  Those currents shouldn't have burnt out the 10R resistor.  The voltages look good, too.