Green Bean problem

[billstein]

Just built a Green Bean and no sound.

I checked for continuity and there is continuity between the wire that goes in and ground but I can't see anywhere where there is a solder bridge.

Also, the diode at D6 was really heating up.

I'm frustrated and at the same time excited about learning how to troubleshoot. Any help would be appreciated.

Thank you in advance.

P.S. How would I measure the voltage of the IC and transistors? Do I go from ground to each leg?

[Stomptown]

I pulled this off of the DIYSB website. Hope it helps:

What to do when it doesn't work:

The following is a "how-to", step by step procedure for getting the most help fastest when your newly soldered up effects circuit just doesn't work. The material is copyright 2005, R.G. Keen, and is displayed on diystompboxes.com by permission. Permission is not granted for redisplay from other web sites without permission in writing from the author.

Gather the things you'll need

A full set of information about what you built
1.Name of the project: Example: Neovibe, from General Guitar Gadgets.
2.Links to the source of the project web site with the schematic or project, layout and wiring diagram. Example : Neovibe
3.Some candid admissions about how closely you followed the suggested layout, if any. If you just perfboarded it, say that, and if you can, include a picture of the board. Scanners do a GREAT job of making pictures of PCBs, by the way.
4.Any parts substitutions or modifications you made to the original. If you didn't have any 10uF caps and used 22uF, say that. If you had to use a 2.7K resistor instead of a 2.2K, say that. If you used a BC109 instead of a 2N3904, say that. By the way, if you substituted any transistors, it's a sure bet that the first question you get asked will be "Did you check the pinout of that transistor?" Delight the questioner by saying (truthfullyâ€) "Yes, I did a google search on that part number and check the pinout against how I soldered it in." If you can't say that, chances are good that you've already found your problem, all by yourself.
5.Whether or not it's a positive ground circuit like a PNP fuzz or a Rangemaster that has been hacked to work with negative ground. This is a special case, but a common one. "Positive ground" means that the positive/red lead of the battery clip is connected to signal ground. "Negative ground" means that the negative/black lead of the battery clip is connected to signal ground when the effect is operating.
6.What it does and does not do how it works; partially or not at all. For instance, if it lets no sound through; or if it makes a harsh, distorted sound only when you strum hard on the strings at full volume; or if everything is really, really low volume.

An electronic meter capable of reading 0-20Vdc and with an ohmmeter scale. This can be analog, but digital ones are available for as little as $10.00. I've seen them as low as $2.99 here in Austin Texas in 2005. If you have to, borrow one. There is really very little anyone can tell you that would help if you can't measure and tell them what voltages you get. It will be much easier if your meter has some way to clip the negative/black lead to circuit ground instead of having both leads with only points. Most meters do. If yours doesn't, you could use a clip lead to do this, if you have a clip lead. Here's a quick guide to how to use a meter in simple laymans' terms. (to be added RGK)

A non-dead battery. Measure the battery with the voltmeter. If it's not over 8.0V, it's going to gum things up and give you inconsistent results. Get a fresh one. Using a DC wall wart is problematical. What if it's the wall wart that's bad? Get a good battery.

A calm, open mind. I don't like to admit this in open company, but one of the deepest episodes of rage I ever felt was when I had been flogging this one poor circuit board to death and even though all the hookup wires and parts were in the right place, nothing worked for hours. I was almost speechlessly angry until I noticed that I was debugging the bottom side of the board for access to all the solder points and had neglected to put the ICs in the sockets. The madder I got, the LESS capable I was of noticing the real problem. You gotta clear your head first.
Being absolutely certain that everything is correct and it still won't work is not good preparation for noticing an errant solder thread, for instance. Mother Nature does not lie, but she is a stickler for details. If it was put together perfectly, it would work. It not working is Mother Nature's way of telling you that you made some tiny error, and it's no reflection on you if it's not perfect the first time.

When you have everything gathered, but before posting, get the specific information you'll report.
1.Hook up the DC power to the circuit (no input signal or amp needed) and clip the meter black/negative lead to signal ground. Probe **every** pin of each IC, transistor and zener diode (if any), and also the battery at the clip and where the battery wires come onto the board. Make a written list of the voltages. Below is a helpful starter list of the minimum things to measure.
2.For extra credit search the forum archives for problems with the same circuit. Someone else may have had exactly the same problem.

(d) Now post. Post all of your gathered information along with the list of voltages along with a request for help interpreting them. Chances are, someone will spot the section that's not running correctly right away. Then a few more secondary tests will likely have it nailed. You'll be posting it to a forum where most of the people there will have been through exactly the same situation. They want you to be successful, and they don't think you're stupid or not cool for having a problem with it.

(e) Learn. There are certain things that always determine what's working and what's not. Read the postings of others that have posted their voltages and find out what happened to them. That way, you get the benefit without having to make the mistakes. Search the archives for problems with the same circuit. Read the debugging page for the indicators about what voltages indicate about function. This last takes a long time, but it's the most rewarding. If I had had a similar forum to learn debugging in when I started this, I'd have wasted a LOT less time in my life.


That's the procedure.

Here is the checklist to fill out:
1.What does it do, not do, and sound like?
2.Name of the circuit =
3.Source of the circuit (URL of schematic or project) =
4.Any modifications to the circuit? Y or N
5.Any parts substitutions? If yes, list them.
6.Positive ground to negative ground conversion? Y or N
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =
Voltage at the circuit board end of the black battery lead =

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C =
B =
E =

Q2
C=
B=
E=

IC1 (or U1)
P1
P2
P3
.
.
.

D1
A (anode, the non-band end) =
K (cathode, the banded end) =

D2
A =
K =

Z1 (zener)
A =
K =

And so on until you get through them all. Having gathered the data, post a tidy list of it on the forum, and you'll most likely have a working effect soon.

For extra credit, while you're waiting for someone to tell you what they see, probe the pins of each of the electrolytic caps, verifying that the voltage on the (+) pin is more positive than the voltage on the (-) pin. If it's not, that cap will eventually fail, whether it's the immediate cause of the thing not working or not.

Yes, it is a pain. But it is a time tested, effective, highly productive pain.

Do this a few times, and you'll start to know ahead of time when something is wrong. You'll be far down the road on learning.

[billstein]

That links great. Thank you, I'll work through that.

I'm curious though about the diode getting real hot. Any thoughts on that?

[Stomptown]

Wish I had some insight but I'm pretty much where you are when it comes to debugging. I've been building a while now but most of my builds have worked out and I've just tossed the fails into a box. I am reading it myself right now and I plan to go back to my very first build to fix it!

[billstein]

With that diode getting so hot, I'm almost afraid to plug the power back in to measure voltage. Who knows what damage I might be doing. 

[jkokura]

Great stuff Jon.

If you guys haven't seen, we have a post about what to do here as well: http://www.madbeanpedals.com/forum/index.php?topic=902.0

As for the problem, Bill, it sounds to me like you have at least one solder bridge to ground. If stuff is getting hot, that's an indication that you do have an issue. Batteries, diodes, and IC's will blow if they get hot, so try not to let that happen anymore.

At this point, I'd take your PCB with wiring out of the enclosure and get some high res shots of the front and back. Elminiate all the offboard wiring you can. Use a testing rig, or rewire you PCB in to just a pair of jacks instead of a switch. Recheck your DC jack, or use an alternate.

Looking at the Green bean docs, D6 is the power protection diode. If it's getting hot, that would indicate that you have power leaking to ground, or a short between your +9V and your GND. If your input seems to be connected to ground as well, by multimeter, than nothing will work until you sort out why that's happening as well. What I'm saying is, your wiring definitely seems to be an issue, and I would highly suspect a solder bridge on your PCB.

Jacob

[billstein]

Thank you Jacob. I know there must be a solder bridge somewhere but have looked and looked and can't find it. I've discovered the bittersweet of having board mounted pots. Had to remove them so I could see underneath. Took forever to get them off.

[Tremster]

Wish I had some insight but I'm pretty much where you are when it comes to debugging. I've been building a while now but most of my builds have worked out and I've just tossed the fails into a box. I am reading it myself right now and I plan to go back to my very first build to fix it!

I will do exactly that as well. Have to make an audio probe, learn how to use it and get the stuff from the shelf of fail working.

[jimilee]

I use a huge magnifying glass to find those bridges.

[pedalman]

check for the obvious. put on jimmys 1" thick glasses look for solder bridges and any reversed polarity
also check the tranny footprints

[Mike B.]

You can usually get away with bending the tabs on those board mount pots a couple times - easier than desoldering them.

And I second Jimi's big magnifying glass idea. Sometimes I even run a toothpick between all the traces if they are close together ...just to make sure there are no bridges.

[billstein]

Thanks guys. I have a 30 power loupe and have looked and looked and can't see anything.

Wish I would have thought about bending the tabs of the pots up. They were a bear to desolder. Am I right in thinking the fabbed  boards are much tougher to remove parts from than etched single sided? I used a solder pump and braid and didn't think I'd ever get them off.