Debugging basics

[Marv Mod]

I'm still new to pedal building and I'm after some basic info on debugging, after a build issue.

I've built a Tonepad Small Clone chorus pedal. Then using Jacob's test rig, I rocked it before boxing it. Problem is, there's no chorusing sound at all. With the pedal on, all I hear is my clean, unaffected tone going through.

That makes me think of a couple of things. Is there a ground issue? Not sure, as the signal is getting through fine.
Next, it makes me think there's a parts issue? Probably, but if I have a dud part, will I still get full signal? I thought any dud part would kill the flow of signal? Maybe I'm wrong?

But am I also right in thinking that if you're getting signal, then there's probably not a soldering problem?

(For those familiar with this project, I've wound the trim pot up and down its range, with no joy).

So my question is, if I'm getting signal through the pedal when on, but no effect, what's likely to be the problem? I know it's cheeky asking for help on a non Madbean project, but I'm curious as to what's happened - I guess this problem could be applied to any pedal build.

Any thoughts would be greatly appreciated! And please correct me if any of the assumptions I've made above are wrong!

Cheers,
Jeremy

[jkokura]

Hi Jeremy. Sounds like your on the right track. A lot of re questions asking are actually answered in this thread here: http://www.madbeanpedals.com/forum/index.php?topic=902.msg5950#msg5950

Jacob

[Marv Mod]

Thanks Jacob, that's a great help. I'll get on with measuring voltages on my main components and triple check everything.

I guess what I was trying to ask as well was whether there were any general assumptions we can make about the results of circuit building? Such as this: no signal = x? (check for grounding, check for solder bridges, bad solder, bad parts etc). Signal with no effect = y (check for dud parts etc)? Signal with hum = z (something else), and so on? So different scenarios rule in or rule out certain possible explanations.

Maybe it's not as clear cut as that and just wishful thinking on my part! I guess I was hoping that as I have signal, but no effect, someone might say "Yep, in my experience that sounds like a component fault, or it's an x, y, or z fault."

I hope that makes some kind of sense!
Jeremy

[petesz]

Do the knobs do anything when you turn them? If not, im guessing its a problem with your wiring. Start with that. Otherwise there could be a solder bridge somewhere on the pcb.

[jkokura]

Maybe it's not as clear cut as that and just wishful thinking on my part! I guess I was hoping that as I have signal, but no effect, someone might say "Yep, in my experience that sounds like a component fault, or it's an x, y, or z fault."

Your welcome Jeremy.

There is usually a "this is my problem" with a "this is my answer," but it's very situational. Because each circuit can be so different from another one, there's no x+y=z answer for all of them. That's why we have the tech help forum, so you can start a thread and get the situational answers.

Really, 90% of all problems come down to a poor installed part (backwards, wrong value), bad wiring, or or because of bad soldering. So if your circuit isn't working, start with looking for and then solving those problems and usually you get a working circuit. When you don't, thats when measuring voltages and getting a more in depth sort of analysis of the circuit done will be important.

For the record, I still have to debug my builds, even though I've built tonnes more than average. I had a Pastyface that was kicking my butt for months until I figured out I had switched three resistors around! I still have a Forum Vibe I have to get working too.

Jacob

[TNblueshawk]

Jeremy, I'm not totally sure what you are saying so let me ask. Are you saying you get a signal in bypass? Then when you stomp that switch does the LED come on? If so, you still get a clean signal as though you are in bypass?

[jkokura]

I've built a Tonepad Small Clone chorus pedal. Then using Jacob's test rig, I rocked it before boxing it. Problem is, there's no chorusing sound at all. With the pedal on, all I hear is my clean, unaffected tone going through.

Jeremy, I'm not totally sure what you are saying so let me ask. Are you saying you get a signal in bypass? Then when you stomp that switch does the LED come on? If so, you still get a clean signal as though you are in bypass?

Technically this should go over to the tech help forum, but for the sake of the discussion...

This is a perfect example of what I'm talking about. In context, this means different things with different pedals. For example, if you had a distortion pedal of some sort then clean signal in bypass and while engaged would mean that your clipping or gain circuit is not working correctly. That means you may have a soldering or wiring problem. it is theoretically possible for this to happen in a drive pedal, but very unlikely.

On the other hand, the Chorus pedal Jeremy's working on would potentially see this problem often. Chorus pedals work by splitting your clean signal, then applying an LFO driven pitch shifting modulation to just ONE of the sides of the split signal. That means that you have a clean path (dry) and a chorus path (wet). If you hear just the wet signal that means you have a problem in the dry path. If you hear only dry signal you have a problem with your wet path, as is found in Jeremy's build. The problems are myriad in that situation: backwards, wrong, faulty or poorly soldered parts are the big candidates, but power issues could also be the issue too. Without a full workup chances are I can't say for sure.

See how context matters in debugging? That's why it's very hard to create an x+y=z formula for helping, rather it's better to have a situational analysis. I had tried to start working on a page in which we could begin to list all the potential problems in debugging and post the solutions, but I quickly began to realize that 9 times out of ten the problems turn out to be, "I used the wrong value resistor/cap in Rx/Cx" or, "my wiring seemed to be messed up" or "I reflowed some fishy looking solder points and it seems to work fine now."

Hope that helps you guys understand how tech help works a bit better. I will add that, as I showed above, understanding how an effect works, like in the case of a chorus pedal or an overdrive, will really go along way to helping you fix things.

Jacob

[Marv Mod]

Thanks so much for the help Jacob, you've answered my question - basically there are too many variables about circuit building for us to say it's likely to be x, or it's likely to be y etc.

And thanks for the note about how a chorus works, that will help a lot in isolating areas that could be at fault.

Cheers,
Jeremy

[TNblueshawk]

Glad I could help and accidentally be the foil Jacob