SOLVED Looking for some help with my Madbean Edgelord

[peccary]

Hey everyone,

I'm having some trouble with this build and I'm hoping someone can point me in the right direction. Here's the build docs.

The pedal works well in Wah mode and Synth 1, but on Synth 2 I am getting very low volume as well as some scratchiness.

I went through and measured the voltages and was getting some wacky readings on the voltage regulator as well as a few pins on the LM 13700. I also adjusted the trim pot to the correct 7 volts.

On the regulator I'm getting I - 9.33 (fine) O - 7 (fine) and on the ground I am getting 5.76. I don't know what's going on with the ground because according to the docs it ought to be at 0, so this one is weirding me out.

On the LM 13700 most values are pretty close but there are a few that are pretty far out of whack: 1 reads 0.96 (should be 1.12), 5 reads 2.19 (should be 5.9), 7 reads 2.18 (should be 5.9), 10 reads 2.02 (should be 5.82), and 12 reads 2.07 (should be 5.83), 16 is 0.96 (should be 1.15).

I'm hoping that this is a bad regulator or chip that I can replace and that someone can tell me that based off this information, but if I need photos of the I can grab some. The 4558's and transistors all align somewhat well with the reported necessary voltages, though there is some variance. the ones I listed above were way off. I haven't had a chance to go through it with my probe yet, but I won't have time for that for a few days, at least, so I thought it couldn't hurt to ask here. It seems odd to me that it would work perfectly in two of the three modes, or at least that makes me think that it's something specific and that someone might be able to point to something based off this info.

Here's a photo of all of the values I got written out on the build docs that list the correct voltages if that's helpful:

New item by Joe B

photos.app.goo.gl

Thanks for your help, folks. I really appreciate it.

 

[Bobbyd67]

Yeah, R15 is two resistors in parallel. It looks like it's touching R47 in the photo but it's above it, not touching.

Brian has been helping me out over on MB and has a few things that I still need to try out from his recommendation. Here's the MB thread for anyone interested: https://www.madbeanpedals.com/forum/index.php?topic=33596.0

I'll update this thread once I get the issue resolved.

Edit to add: R15 should be two 15k resistors, but looking at the resistor colors I'm not so sure that's what I have there (I'm a bit colorblind). I'll have to double check when I get home and can look at it in person and compare it. Looks like I might have 1M5 there instead.

Yeah looking at the pic a see a brown(or black), green,black, yellow, brown bands so either 500k or like you said 1m5. Should be brown green black RED brown for 15k if the digikey color band calculator is to be trusted^^

 

[peccary]

So I'm a dummy and soldered together two 1M5 resistors instead of two 15k resistors for R15.....

I had lots of help on this, but it was @Bobbyd67 drawing my attention to R15 that made me take a closer look. I didn't look over my combined resistors because I spent a good amount of time making sure they were right... That'll show me.

Thanks again for everyone who helped out, I really appreciate it.

 

[Feral Feline]

That’s sorta like me copying the wrong value from the Mole (390 Ohm) onto my schematic (390k), then checking all the resister values against my schematic… “390k… check”

I never did get a chance to check resister values on your build, Joe, glad Bobbyd67 did!