My son and I just finished the soldering. It worked twice and then kind of stopped. I’ve removed the 9volt but now when I plug it in, it randomly lights up a single led. The battery is good, still reading slightly over 9 volts. There doesn’t seem to be any bridged pads. Any ideas would be much appreciated.
Most likely a mechanical problem such a bad soldering, loose pcb track or pad, crack, intermittent contact etc…