• Debugging

    Keith • 06/30/2025 at 00:05 • 0 comments

    Okay, it doesn't work. Now what?

    One can start with a visual check.

    • Transistor flat edges on the correct side? Yes.
    • Capacitor stripes on correct side? Yes.
    • LED flats on correct side? Yes.
    • Resistor stripe colours correct? Yes.

    Well it looks like it was made correctly.

    The Ground wire pad has come off the board, that will need fixing.

    After that a multimeter is an essential basic tool for any electronics hobbyist.

    First step, find the circuit diagram.

    Find the picture of the board with the component identifiers 

    Common faults include:

    • Dry solder joints
    • Heat-damaged components

    I have the good fortune to have a working version to use as a reference.

    I took a picture of the PCB tracks.

    Current consumption: 83.8 nanoamps, so it is not shorting anything to ground.

    Observation: There is no activity at all. The fault is causing BOTH transistors in BOTH flip-flops to be in the off state. 

    9 volts on one resistor but not three others - found a PCB track broken. 

    Fixed, and one flip-flop works.

    Heated a few dry-looking joints on the other flip-flop, and now it works.