Need help with Penrose build

edited October 2015 in Troubleshooting
I have been building a Penrose. I feel like a fool, but I can't get it working properly:
  • Note on/off LEDs work
  • A CV in doesn't do anything
  • The 4 highest notes change the pitch when turned on/off
  • When one of the other 8 notes is turned on, the pitch turns to the same very high tone
  • The trimmer does not seem to influence the pitch

  • I'm sure the big capacitors aren't touching anything, clipped everything close by
  • Can't find solder bridges
  • Diodes correct orientation, current flows one way
  • IC's have correct orientation
  • Checked schematic, it seems that row3 is only working ? But now what ? Paths of rows 1-3 from Atmega to other board all seem ok
  • Checked all resistors with a multimeter. Here's when things get strangs, the 100k resistors measure this:
r7 99k
r20 100k
r2 51k
r9 51k
r14 104k
r15 99k

Checked and double checked resistance and color coding. How can this be ? Please assist, any ideas ?


  • Unfortunately you cannot measure resistors when soldered. Check the color codes instead...
  • Ah right, ofcourse, current might flow another way round. Color codes are ok.
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