LMNC MS20 Filter Low Output

DIY STUFF
32

So after a local oops :smiley: that required a bit of debugging, it struck me that a quick way to check the CV converter is to measure the bias current (aka “Iabc”):

  • set your multimeter to microamperes (µA) if it supports that (otherwise mA might work, if it can measure with at least 2 decimals).
  • power off the board, unplug CV in, and set the cut-off potentiometer to somewhere in the middle
  • carefully remove the 13700 from its socket
  • power up the board, and measure the current between pin 1 (and/or 16) and ground, while sweeping the cut-off pot between the end points

You should see currents between ~0 and 60-80 µA. If you see no movement, or you’re getting a lot more (more than 1-2 mA or so) something might be broken. Very low currents here might also affect the overall output volume afaict (I should do some calculations to figure out what an acceptable minimum bias is).

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