stan2004 posted:How many switches on your layout? And to be clear, you're referring all the lamps dimming when one switch is thrown?
If the aux power wiring to multiple switches is a daisy-chain, then it seems switches closer to the transformer will see less drop and might actually get brighter if some kind of boost method is used!
Is conversion to LED a viable option? Note that this would likely require more than swapping out the existing filament bulb for a basic LED equivalent. The LED must have some kind of voltage regulation or energy storage (capacitor). Why? Because you will still see the same voltage drop from the large momentary solenoid current! So there must be circuitry at each switch which I suppose could be considered a bother to hook up.
If attempting to "boost" the voltage at the transformer (rather than regulate/smooth the voltage at each switch), my guess is converting to all DC operation might make for an easier circuit whether staying with lamp or converting to LED.
Thanks for the thoughts. With my current "concrete floor empire" I have about a dozen switches - and they are all illuminated with incandescent lamps (although the switch panel uses LEDs). So the transformer sees about a 1A load in steady-state. The switches are powered in a semi-daisy chain configuration with a couple of low-gauge feeders which then branch out so the effect is by-my-eyes about equal among all of the switches.
As you point out just converting to drop-in LED lamps might not make much of a difference as the voltage drop upon solenoid activation would still exist - although, perhaps, not as noticeably depending upon where in the LED's operating range the steady-state voltage resides (which is about 13V, at least at the panel).
The situation is certainly not a show-stopper by any means, so I'd probably say converting to DC switch operation and having localized filtering is hunting flies with a bazooka. I might end up doing a test with the DC boost to see if it makes any real difference - else, it will just remain one of those charms of PW Lionel layouts. 
