Autobahn

[TreeSlayer]

welp, still battin 1000... as usual, it doesn't work. everthing is set up bone stock. i've removed C9, REG1, R27 and C4. it sounds the same. i think i'm on the circuit with the problem. any thoughts?

LT

[jimilee]

So,you have sound?

[midwayfair]

Try the audio probe yet to trace the dry path?

Check continuity against the schematic?

Post voltages on all chips and transistors?

Half the builds I do require some minor trouble shooting, and there was a point where I batted 1000 with anything that wasn't a fabbed PCB, too. Don't get discouraged. Expect it!

[TreeSlayer]

So,you have sound?

strangely enough, yes....

[TreeSlayer]

Try the audio probe yet to trace the dry path?

Check continuity against the schematic?

Post voltages on all chips and transistors?

Half the builds I do require some minor trouble shooting, and there was a point where I batted 1000 with anything that wasn't a fabbed PCB, too. Don't get discouraged. Expect it!

#1. no, didn't think about it. really not sure what i'm supposed to poke at...

#2. yes, i tried, but there are two caps that i can't read the values on. values from another part are printed over it.

#3. i'm going to check that tonight. it was late by the time i got to that point.

thanks for the encouragement. i've actually gotten over being discouraged. and i fully expect them not to work. i built a retrograde over the weekend because i was waiting for parts on this one. it doesn't work either. and it's identical to the one i have that does work. go figure...

[madbean]

It happens to everyone at all levels. I expect at least half my ideas/builds not to work. The only time that it should be discouraging is when you don't know what to do about it. This is just a matter of practice. Learning to read schematics, even if you don't fully understand how everything works, and using that knowledge to identify potential problem areas will go a long way toward quick and easy debugging.

The most fundamental thing to look for in reading schematics is identifying the path the guitar signal takes from input to output. Each stage of that progression usually involves some kind of transformation, either through a transistor, an op-amp or a filter. And each of those transformations has an input and an output. So, if you are looking to find out why your signal isn't getting through, it is simply a matter of knowing where those individual transformations occur, where the signal comes in and where it is supposed to leave. Then you use the audio probe to trace those inputs and outputs along a linear path from effect input to effect output.

Here's a simple example using the input stage of the Mudbunny. Red dots are all the points you should have some audio. Yellow checks are places you should have DC voltage. Green arrows indicate the signal flow. As you can see, with just a few parts there are already nine places where something could go wrong. Maybe your input cap is bad or has a solder bridge. So, the signal never gets through C1. Or, perhaps your supply voltage is off so you are reading 2v at the top of R6 instead of 9v. Then your transistor is not functioning properly and the signal never gets to C3.

Obviously, you don't want to have to check all these points right at the outset. So, what you do is identify the input and output of this "transformation" and stick your audio probe to find out where your signal is. In this case, the base of the transistor is the input and the collector is the output. If you have signal through both, then move to the next transformation. If you have signal in, but not out, then you need to start checking these components in this area: are they soldered correctly, do the correct components get the voltage they need, could the transistor be the wrong type, or backwards, etc.

Once you start practicing this kind of thing, it becomes much, much easier to debug your builds. Even if you don't understand exactly how it is supposed to work, you can at least get a handle of where the signal comes from and where is it supposed to go.

[TreeSlayer]

and there ya go! now it makes sense. thanks a million, Brian! i really appreciate you taking the time for this. i can read the schematics somewhat, but i do tend to get lost most of the time. seems like it goes in circles sometimes. but being you put it that way, it's clear as a bell. really no different from diagnosing problems with a drag car. now i can't wait to get home to fix this critter!!

LT

[TreeSlayer]

welp, still battin 1000... as usual, it doesn't work. everthing is set up bone stock. i've removed C9, REG1, R27 and C4. it sounds the same. i think i'm on the circuit with the problem. any thoughts?

LT

well, still no luck. as i stated before, i can remove all of the parts above, and i still get sound. just not the wah part. i would have thought that if i took a part off the board, i would have an open circuit and there would be no sound. it's seems like i have a short, bypassing the section that makes the effect, but i just don't see anything. any thoughts? thanks a million in advance!

LT

[TreeSlayer]

thanks to JimiLee, i may have found my problem. i have C9 as a 2u2 polarized cap... thoughts?

LT

[jimilee]

thanks to JimiLee, i may have found my problem. i have C9 as a 2u2 polarized cap... thoughts?

LT

I looked on the schematic and the BOM and c9 is not polarized,why/how do you show it poarized?

[blue_tokai]

I put a 2.2uF electrolytic in for C9 myself and it works...... make sure you have the positive side to the base of Q2

[TreeSlayer]

thanks to JimiLee, i may have found my problem. i have C9 as a 2u2 polarized cap... thoughts?

LT

I looked on the schematic and the BOM and c9 is not polarized,why/how do you show it poarized?

i don't show it polarized. it's just all i have...

[TreeSlayer]

I put a 2.2uF electrolytic in for C9 myself and it works...... make sure you have the positive side to the base of Q2

well then apparently that's not the problem. i've put it in both ways and no positive result...

[blue_tokai]

You said in the previous post it was/is a polarized 2.2uF... I know the schematic and the board layout dont show it as marked, but if it is a polarized cap then the pos needs to be at the pase and the neg (marked) is going to the ground pad.

[TreeSlayer]

You said in the previous post it was/is a polarized 2.2uF... I know the schematic and the board layout dont show it as marked, but if it is a polarized cap then the pos needs to be at the pase and the neg (marked) is going to the ground pad.

i have this socketed, and tried it both ways. no change...