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Dirtbaby No Modulation

Started by barnaby, April 17, 2019, 09:42:10 PM

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barnaby

I built a run of 3 Dirtbaby pedals and all of them are having the same issue: no detectable modulation.  Reflowed connections, no change.  When checking values, I found R32 and R33 were reading 50k, rather than the 100k in the schematic.  Eureka!  I pulled both of them out and put in two 100k that i tested beforehand.  But, when checking them in the pcb, they read 50k!  Any idea what is causing this?

madbean

You generally cannot get accurate readings on resistors in circuit. Always go by the code on the resistor itself.

As far modulation goes, not enough info to provide any advice yet.

http://www.madbeanpedals.com/forum/index.php?topic=902.0
http://www.madbeanpedals.com/forum/index.php?topic=26664.0

barnaby

I tested the voltage on all the IC pins, they are in spec with the build.  I can provide them if you want.
When testing with an amp, I found that with the switch in the vibrato position, I can faintly hear a pitch from the amp that rises in frequency when I turn the rate knob clockwise, but dissapears when the knob is at full.
Thanks for your help!

barnaby


zgrav

It is interesting that you have this result from 3 separate builds for the pedal. 

zgrav

what caps are you using in c3 and c33?  (2.2 UF np)

barnaby

Quote from: zgrav on April 18, 2019, 07:15:09 PM
It is interesting that you have this result from 3 separate builds for the pedal. 

I know, right?!?!?  Leads me to believe that I have a bad component/something that is the same on all 3 boards. 
Quote from: zgrav on April 18, 2019, 07:21:16 PM
what caps are you using in c3 and c33?  (2.2 UF np)
You found it!  I have 2200nf instead of 2200pf... gonna order the right parts this time  ;D
Thanks for the extra set of eyes!  I'll update on the results.
-Barnaby

barnaby

PROBLEM SOLVED ;D ;D ;D ;D  Turns out it works just fine with the proper values... Thanks for the extra set of eyes!