Author Topic: In case your DOA doesn't work as expected

December 17, 2020, 11:47:34 AM
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1. Check the usual suspects:
  • Forgotten solder joint,
  • Bad solder joint (reflow suspicious joints),
  • Reversed components (diodes, transistors),
  • Flipped transistors,
  • Trim all the component leads as short as possible. Nothing must touch the PCB below.
2. Also:
  • make sure R1 is not touching the vertical PCB and the diode D5,
  • check you didn't flip the power transistors Q9-Q10,
  • check that the 4 solders on each vertical PCB are making good contact,
  • check you didn't reverse the LED (it must light up),
  • check you didn't swap D4 (Zener) with one of the 1N914.
Other than this, the DOA's are very difficult to repair, I would recommend that you build a new one.
« Last Edit: December 20, 2020, 09:28:02 AM by JPK »