Here are some things I found while researching this system.
There is not any information in the service manual discussing this system, that I could find. Service manual pp 18-74, Plate H16 is the schematic plate I used.
The three transistors that control cockpit light dimming are common 2N3055 transistors, about a dollar apiece. (Some earlier 337’s may have two transistors.)
To test a transistor, find a schematic for the transistor on the web and connect a multi-meter: red to the collector (the collector is the outside of the case of the transistor), black to the emitter pin and a jumper cable from the collector to the base pin. Resistance readings of 12-15 mega ohms seemed to be usual for the 17 2N3055 transistors I tested. I discarded those resistors with less than 10 mega ohms.
- The top transistor on the transistor panel controls the dimming of the under glare shield flood lights (except for the center flood/registration number light, which is illuminated at full intensity continuously).
- The middle transistor controls (in my case), the center under glare shield flood/registration number light, and the dimming of the instrument panel post lights and integral instrument lighting.
- The bottom transistor controls the post lights on the pedestal.
- Your mileage may vary.
The inverter is termed an “Inverta-Pak” and has Cessna part number C613001-0101 made by Astronics with manufacturers part number 71254-6, or Scott Aviation number 804134-01. Cessna 310 model P,Q & R have this part as number 9910047-1, Piper PA-46 has it as number 9910039-1. Cessna 210 L & N also use it.
Rick