Every circuit board I sell need to be thoroughly tested, and measurements taken that should agree with expected values. Tests are chosen to show up any errors I might have made in the board’s assembly.
- Gain. I use 0.1% tolerance resistors in key parts of the circuit, so gain should match within 0.01db from one board to another.
- DC operating points, such as the drive voltage to the output sections, DC offset, DC servo output, and bias voltages
- Distortion; it should match measurements from other boards, all the way up to full-scale output.
- Current running through various branches of the circuit.
- Functionality of indicator LEDs
Here’s how I build my test jigs.
Long story short: Printed circuit board+Pogo pins=Test jig.