N4ZQ has dual Lightspeed Plasma III ignition.
Each module is grounded directly to its respective Odyssey battery.
Each module gets power through its respective switch by way of a 5A breaker, directly from its dedicated Odyssey battery.
Both Plasma III modules are factory wired to the panel LCD display which shows RPM, MP, and ignition timing degrees for each unit.
I couldn't figure out why the LCD display showed 12-14 RPM when the Plasma III's were energized but the motor wasn't running. Through process of elimination, each system was powered down without effect until I pulled the MVP-50 breaker. At this point, the Lightspeed LCD RPM display dropped to zero. I should point out that each Plasma III module outputs a 5v square wave for RPM and these outputs are received on pins 25 & 26 of the MVP-50 bottom EDC connector. So, the Lightspeed LCD display was receiving a miniscule voltage from the MVP-50. Whether any of this matters remains to be seen when I light off the motor for the first time...

If anyone on this list has a 4cyl Lycoming, dual Lightspeed Plasma III with Simpson LCD display AND an MVP-50, please contact me directly.

Thanks,

Angier Ames
N4ZQ