Electronic Lamp Dimmer AA5-B

An exact replacement for the the high-power rheostat that controls the lighting in our planes hasn't been available for years. When mine became intermittent, I decided to install an electronic dimmer and obtain field approval via 337.

I chose the model DM30-14 available through B and C Specialty because it seemed well designed and engineered (by guru Bob Nuckolls of Aeroelectric Connection) and moderately priced. My friend Steve Williams and I did the installation, which was surprisingly easy. Our work was inspected by my IA, who obtained an unremarkable field approval.

One item in the 337 parts description needs explanation: why overkill on the dimmer control (I used a 2-watt potentiometer)? Well, to maintain authenticity I wanted to reuse the orginal knob from the rheostat, but found that its shaft was far too large for the 1/2-watt potentiometer I had intended to use. So, I bought the smallest potentiomter whose shaft fit the knob--which turned out to be a 2-watt model. Even if you don't care about using the factory knob, I'd still recommend using a potentiometer with a large shaft, because a smaller shaft will wallow in the over-sized panel hole, which no IA in his right mind would approve. The 337 for the Aero Electric Connection lam dimmer is at:

http://www.campbells.org/Airplanes/337s/index_Airplanes337s.html