How do I find a short to ground?

[Cardboard Tube Samurai]

After debugging and troubleshooting endlessly for the last week, my Rat is sending me up the wall! I am getting signal to the board and through the first cap but it won't travel any further. I have triple checked that the polarities of all of the electrolytic caps are right, all of the pinouts on the transistors are right, all of the diodes are flowing the right way. I can't see anywhere that it is grounding out but I suspect that is the problem. I can't get voltage readings on anything past the first resistors.

I am using a sine wave for the signal (I have spent a lot of time on this and got sick of strumming the guitar to get signal) and I have noticed that there is an extremely low strength signal that seems to be present when I probe the enclosure (metal).

I have made other pedals before but this one really has me stumped! Can somebody please give me some pointers as to the possibilites of what it might be? PLEASE!?!?!?!?

[GibsonGM]

If you've done-it-yourself before, I'm not even going to ask if you have power to the things that need it, etc, LOL; that's the 1st thing I'd check.   The lack of signal after the cap makes me suspect its orientation, or that it may be blown...try paralleling a small value one across it maybe?  After that, the it's magnifying glass, schematic & a good light to find a short.  Maybe someone else has another way to spot shorts, but that's all I've got!
Good luck

[Cardboard Tube Samurai]

There is signal after the cap and it is also non-polarised (greencap .02uf). Signal is getting to the resistors after the cap, but not past them.

[petemoore]

I can't see anywhere that it is grounding out but I suspect that is the problem.
  I would test for ground to confirm/deny suspicions of ground where it shouldn't be, using DMM.

[petemoore]

  Debugging Thread has proved useful to get circuits working.

[Paul Perry (Frostwave)]

You find a short to ground the same way you would find a leak in a pipe: you cut the pipe in half, and see which end will hold water. Then you cut the faulty section in half, and so on.
OK, we're using electrons... but it's the same.
But as other posters say, first check that there IS a short to ground. It's impossible (at least, for me) to debug without a continuity checker multimeter. Beep beep!

[Paul Marossy]

It's impossible (at least, for me) to debug without a continuity checker multimeter. Beep beep!

+1

[Ed G.]

Yeah, to do this, you need to have at least a basic multimeter with continuity function. I find myself using mine all the time for all types of things (testing batteries, fuses, etc.) and I couldn't troubleshoot a pedal without one. You can get a basic one from the Radio Shack for about 20 bucks.

[Cardboard Tube Samurai]

  Debugging Thread has proved useful to get circuits working.

Yeah thanks for that. I don't know if you read my whole post, but I did mention that I had been debugging and troubleshooting for a week before I posted this... you should have saved yourself the trouble of replying by reading!

To everyone that mentioned the multimeter thing, cheers! I am a bit of a noob at using a multimeter but I will give it a go and see if I can figure something out. I just don't get it, this is the cleanest, most well put together board/pedal I have made yet it is giving me the most trouble!

[jimmy54]

Cardboard.  Pete offered you a useful suggestion then also posted that the debugging thread contains useful information that may help.  Your reply to him came across as extremely rude (but maybe that's just me).  Mind you, maybe I should have saved my time and not replied

[petemoore]

you should have saved yourself the trouble of replying by reading!
  well I re-read it.
  Still, I don't see anything much of use in it other than 'it doesn't work'
  A DMM is a debuggers best tool. Beyond if it just happens to be..this or that, It makes the process possible.
  Perhaps after having read and followed the debugging page, and doing some successful debugging, you'll see that the pertinent information [outlined in the Debugging thread] is necessary to progress with any certainty beyond where we are now...

[george]

The idea of the debugging thread is to go through it then come here and say

"I did this, this, this and this all as per the debugging thread, it still doesn't work.  Here are the voltages and stuff that the debugging thread told me to measure".

THEN you can slag someone off for not reading your post ...

some other info would be handy as well:

Like:
- "I am using the GGG layout/Torchy's vero layout/perf/<other>"
- some voltages esp. on the IC pins

I second the "beep, beep!" too

[Paul Perry (Frostwave)]

I can't get voltage readings on anything past the first resistors.

In that case, there can't be any power getting to the rest of the circuit, can there?
So I'm thinking something might not be connected. Try doing the BEEP thing again, but this time to check (while power is off) that every component is connected to every other component that it should be.. putting your meter probes on the legs or pins of the components, not the solder, which may be a dry jont.

[R.G.]

I can't get voltage readings on anything past the first resistors.

Then something is dead right after the first resistors, yes?

Can somebody please give me some pointers as to the possibilites of what it might be? PLEASE!?!?!?!?

Unfortunately, IT COULD BE ANYTHING.

That's what the organized, ordered disciplined approach in "What to do when it doesn't work" is all about. It's a general way to quickly sort out the wheat from the chaff, and let a person with some experience make a good guess about what is wrong, not just say "...hmmm... could be your filter cap's shorted, or your A-frame is busted, I guess."

[Gilles C]

First, I would confirm that you really need to use a steady signal to debug, not a guitar.

Second, I normally find that it is easier to debug a circuit that doesn't work at all than one that works, but not correctly. Maybe it's only me, but that's my feeling.

Third, the only thing to do is what is suggested in the precedent posts.

A short to ground is also what I suspect because you detect a signal on the case, which can happen because there is some resistance between 2 ground or between the ground and the case, even if it's very small, but the signal detected on the case is also very small.

And again, as suggested before, you won't find it without splitting the circuit and start disconnecting some parts. Also use a magnifying glass to inspect the board for shorts.

Gilles

[Gilles C]

After thinking again about it, I began to think that it could be more a short to the case more than a short to ground. Like a screw holding the board.

Do you also detect a signal on a ground?

Gilles

[Cardboard Tube Samurai]

Firstly, I apologise for being abrupt in my reply before... I had just woken up and was a little hazy in the head. Please forget I said anything at all in that post!!!

Now, I have tested the entire thing for continuity and it doesn't seem to be an issue. I am going to leave it for the weekend to figure out because like I said, it's doing my head in. I appreciate the responses and you peeps have given me more places to look than I could have ever figured out by myself. I guess I just have to do yet another "idiot check" of the setup.

[Cardboard Tube Samurai]

I found the problem! It's funny how you can be working on something for so long that you can just completely miss something really simple, then when you have a break for a day and look at it again, you spot the problem straight away.  It was this thread that pointed me in the right direction though... In particular Paul Perry's comment re: power not getting to the rest of the board. I used the GGG layout and didn't bother wiring in a DC input jack because the person I was making it for only likes using batteries. Because of this, I didn't have a wire providing power to the next point along the board. THERE WAS NO SHORT TO GROUND!

Let it be a lesson to anyone starting out... sometimes it pays to leave it for a bit when it is frustrating the hell out of you and come back with a clear head!

[R.G.]

Let me apologize if this sounds like I'm saying "I told you so." Although that is how it comes out, the point is to help others learn.

I completely agree with you that taking a good long break helps you see things that you were missing earlier. In fact, the more frustrated you are, the less likely you are to find problems. The emotions blind you.

But there is also another lesson. The approach in "What to do when it doesn't work" would have turned this up immediately if done properly.

If you had checked voltages to each active device on the board, you most likely would have found not only that part of the board was not getting power, you would have isolated which stages the break happened between.

The "What to do when it doesn't work" approach is a structured approach that substitutes rote activity for insight. Unthinking activity is not as easily blinded by emotion and preconceived ideas as searching for insight is. That's one reason it's effective - it's automatic, and it collects a lot of data that will catch seemingly unimportant info that in fact points to the problem.

Again, I apologize - I am not taking a poke at  you, I'm trying to help the next guy.

[Cardboard Tube Samurai]

No offence taken R.G.! Although I have made a few pedals, I still consider myself fairly new to the process. I had gone through the "What to do when it doesn't work" section thoroughly, but for some reason missed it... what can I say? I am only human. The more frustrated you are at the project, the more likely you are to come on to forums like this and get shirty with people when they don't give you the answer you want...

On a side note, if anyone else wants to make this pedal using the GGG layout, I highly recommend substituting a 50k log pot for the drive instead of the 100k.