High level troubleshooting of a diy TS808

[alphadog808]

Hi guys,
   So I built a ts808 on vero(I know, I know- ) and it worked fine unboxed.  I then boxed it, and it STILL worked. I added on the plastic knobs, plugged it in and got ready to test it.  Now it didn't work.  I opened it up thinking the usual, pot touching case, something else grounding out, etc. 

The only suspicious thing I found was the 9v rail looked like it had been touching the case(ground).  However, even after remedying that, the pedal is dead silent when engaged.

I get a bypassed signal, so the cables, amp, etc is good.  LED lights up, so I have power.  It worked before, so the board should be ok, no solder bridges, etc. 

What I'm wondering is could that 9v rail possibly kill the:
opamp
2N5088
1n914

on the board?  I figure all the other components could handle that short...?

I have a LM833 from another board that I popped in, no dice.  Unfortunately, I don't have any spare 2N5088s, I only have spare J201s and 2N5457s and I don't think I can swap those for testing.  Now that I think about it, I might have a 1n914 or two lying around I can test, but the ones in the board look ok.

I guess my question is, any thoughts on what might be bad?  Is there any quick and dirty way I can get around the 2n5088s to see if they are bad?  I'm planning on busting out my audio probe on it tonight but was hoping I was missing something...

[mth5044]

Voltages!

[Mark Hammer]

It doesn't take much current to light up an LED.  It can take more current than an LED requires to actually power the rest of the circuit.

Any possibility that you wired up a battery connection to the input jack incorrectly and the battery nearly drained overnight, leaving you with just enough juice to power the LED...and only the LED?

[alphadog808]

Mark, I was actually using a wallwart, so the power should be consistent.  I also went over the pots with a multimeter and they seem ok.  I was having some problems putting the knobs on, so I thought, maybe, just maybe I broke the volume pot...

[pappasmurfsharem]

Mark, I was actually using a wallwart, so the power should be consistent.  I also went over the pots with a multimeter and they seem ok.  I was having some problems putting the knobs on, so I thought, maybe, just maybe I broke the volume pot...

Done that before, I was very upset. although the pot "became loose" when it happened and I hadn't realized it.

[Mark Hammer]

Mark, I was actually using a wallwart, so the power should be consistent.  I also went over the pots with a multimeter and they seem ok.  I was having some problems putting the knobs on, so I thought, maybe, just maybe I broke the volume pot...

Sometimes jiggling around pots while installing can result in a wire fracture.  Any possibility of that?

Not dissing your chops.  Just trying to figure out what it isn't.

[alphadog808]

Not dissing your chops.  Just trying to figure out what it isn't.

I want you to diss my chops!      I posted this in hopes of thoughts/ideas that I might have overlooked that might be causing it.  I didn't think of a wire breaking, I'll have to check continuity.  Thanks to you all for the help. 

Pappa smurf, I did have to manhandle the knobs a bit, but they still felt fine and the multimeter was reading right when I turned it with probes on lug 1/2 and 2/3.

So you guys don't think the 9v touching the ground could have fried components?  It hasn't in my previous pedals, but ya I figured, ya never know.

[LucifersTrip]

Voltages!

+1

this is almost always first...unless you enjoy reading guesses

[R.G.]

"What to do when it doesn't work" tells the tale.

[alphadog808]

this is almost always first...unless you enjoy reading guesses

Intelligent guesses are fine; things like papa mentioning about broken wires is something I didn't consider; it's helpful to me.

I guess to clarify as I don't have voltages yet is, would it be pretty likely I could have blown up the diode, op amp, or/and transistors with the 9v rail touching the case/ground?  This circuit was working 100% unboxed, 100% boxed, but only stopped working after I attached the plastic knobs(coincidence assuming it's not the pot). 

I can easily test the diode(will tonight, hopefully) so I'm really more concerned about the transistor.  Looks like I might be able to jimmy a j201 to work in the 2n5088 if I change the leg order, maybe I'll try that as well if I have time.

[alphadog808]

Problem solved.  I checked the wiring, no broken wires.   I unscrewed the pots from the case, it suddenly works...checked the pot holes in the case.  Not much to write home about, but maybe a small missed bit here and there of dried Park's superglaze.  Scraped it off, put it back in, it works.     I'm guessing maybe that stuff is conductive and maybe was touching one of the pot pins and shorting it out...   Either way, it's all good; thanks for the help, guys!

[ashcat_lt]

No schematic and no voltages so just get out the shotgun! 

But the answer is no.  A direct short from 9V to ground bypasses all the parts you mentioned.  No current through them because it's all going the easy way.

[alphadog808]

*click* *click* boom!       I figured since it was working very well before it was boxed and when it was boxed, I didn't want to initially delve too deep into troubleshooting the board as most likely it wasn't the problem.  I had a sneaky feeling it was something more simple or I damaged a component during a move.  If I hadn't have figured it out soon, I was then going to bring out the sniper rifle.     Luckily, I didn't need to.

Thanks for all the feedback guys, it helped.

[LucifersTrip]

sounds cool...but note that the voltages (which take a minute or two) would've shown the dead short instantly