[Al Skierkiewicz]

The loose negative power supply lead and the improper wiring for the radio are enough of a smoking gun for me. The battery will regularly drop to eight volts in a complete direction reversal. All motors are going through excessive current draw so the voltage drop across the internal resistance of the battery and the wiring and breaker feeding the PD is enough to cause this in four motor drives. The three terminal regulator is only speced to maintain output voltage down to about seven volts input. It is for this reason, the voltage regulator must be wired to the 12 volt radio output of the PD. That output will maintain voltage down to about 4.5 volts on the battery input.