A one-knob panel dimmer is getting less possible with a mixture of old and new avionics. The old devices had incandescent lights that were dimmed by reducing their voltage. Newer devices have LED lighting which draw so little current that the voltage from the original rheostat drops abruptly rather than smoothly, and so does the light from any directly powered LEDs. Worse yet, some of the newer devices have a dimming input that provides maximum light with zero volts applied, and dims as the voltage is increased.

I've ended up just using the overhead red flood at maximum intensity.

And there's even a problem with that: A number of avionics units have a photocell to automatically dim as the ambient light decreases. Several of these, at least, are sensitive to red light and therefore don't dim when the red flood is on. I've solved that problem by taping a little piece of green colored plastic film over the photocells.

Roy

States where I've landed my 150
[Linked Image from eznec.com]