The motor of the 17550 requires 70 volts DC and draws 0.15 amps.  The single 200 watt bulb is rated at 30 volts DC and draws about 6 amps.

The motor of the 20585 gyralight also requires 70 volts DC, but draws 0.25 amps due to its slightly larger size.  When the 200 watt bulbs of the 20585 are wired in series, they operate on 60 volts DC and draw about 6 amps.

The typical locomotive has a 70 volt DC supply.  This makes it relatively easy to wire the DC motors in the gyralights.  Because of their DC operation, reversing the polarity of the supply voltage to the motors reverses the direction of the motors.  The lights are also wired to the locomotive’s 70 volt DC supply.  The voltage to the lights is adjusted by an adjustable dropping resistor.  In the 20585 gyralight, this voltage drop is relatively modest and easy to obtain since the resistor only needs to disipate about 60 watts (6 amps times 10 volts).  The dropping resistor for the 17550 would be much larger and get extremely hot because of the high current and large voltage drop required for a single light (about 240 watts).  Dropping resistors are normally located in the locomotive cab external to the gyralights.  However, the dropping resistor for the 20585 could easily be located inside the gyralight..

Running the bulbs at their rated voltage is fine when they are located outside high on a locomotive.  However, when the gyralights are used for display purposes, some means for dimming the lights is needed to make the lights easier to observe close up.

I wired the 17550 gyralight using 120 volt household AC.  I connected the AC supply through a 2 amp fuse and a 3 amp solid state AC relay to a 450 ohm resistor network composed of 4 100 ohm resistors and one 50 ohm resistor all wired in series.  Each resistor was rated for 10 watts.  The output of the resistor network was then connected to a bridge rectifier rated at two amps and 200 volts to create a DC output voltage.  A 220 uF electrolytic capacitor rated at 200 volts was placed across the bride rectifier’s output to smooth the DC output running the motor.  With the 450 ohm resistor network, the voltage at the motor measured approximately 70 volts DC.  The motor is turned on and off by the solid state relay located between the fuse and the resistor network.  The motor for the 20585 was wired identically with the exception of the resistor network which was 150 ohms composed of three 50 ohm 10 watt resistors wired in series.  With this setup, the 17550 “gyrates” at 60 rpm and the 20585 “gyrates” at 52 rpm.  The motors also run relatively cool.  A regulated supply would of course work better, but would be far more complicated to construct.  Given the adequate operation without regulation, I decided a regulated supply was not worth the extra effort.

Because of the high current requirements for the lights, I decided to run the lights on AC instead of DC.  The AC supply was connected through the same 2 amp fuse to a 3 amp solid state AC relay which in turn was connected to a thin model of household dimmer switch.  The output of the dimmer switch was connected to a 12 volt 4 amp AC transformer.  The 12 volt output of the transformer was then connected to the bulb terminals.  Adjusting the dimmer switch lowers the voltage to the transformer primary which in turn lowers the voltage applied from the transformer secondary to the bulb.  The lights in the 20585 were wired in series and driven with a heavy duty 24 volt 10 amp transformer.  I found the bulbs work best indoors when operated on 6 volts each which is about 1/5 their rated voltage.  At this voltage, each bulb draws about 2.5 amps.  Because these 200 watt rated bulbs are only drawing 15 watts, I expect them to last my lifetime.

Each gyralight is attached to the wall with three lag bolts.  A one inch long 3/4 inch diameter pvc pipe is inserted on each lag bolt to provide one inch of space between the wall and the back of the gyralight.  In the 17550, the dimmer switch is located in back of the circuit board.  The dimmer switch adjustment shaft protrudes from the rear of the gyralight near its top.  This allows the brightness of the light to be easily adjusted.  In the 20585, the dimmer switch is located in back of the transformer and the adjustment shaft protrudes out the back near the bottom of the gyralight. 

For added safety, I inserted a 2 amp fuse in each gyralight just before the solid state relays.  Each gyralight case is also connected to ground. 

The solid state relays controlling the motors and lights are in turn controlled by 12 volt DC outputs on the microcomputer signal controller I built.  These relays could be replaced with AC switches for manual control..

WARNING.  While the circuits are relatively simple, because of the high voltages and currents involved, they can be dangerous and should not be built or maintained by anyone who does not have the requisite electrical/electronic experience.

Above.  I acquired the gyralights by placing an ad in Trains magazine.  The 20585 arrived in the condition above.  The top of the unit is at the far right of the photo.  The visors are mounted underneath each bulb to prevent the glare from reflecting off of the locomotive hood into the engineer’s eyes.  You will note that this unit has a flange and was originally surface mounted..  I called Trans-Lite to see if housings without flanges were available, and they offered to exchange the flanged housing for a housing without a flange at no charge.  I assume that the flanged housing, being made for more modern locomotives, are in greater demand.  The 17550 was delivered in restored condition.  It just needed a little touch-up painting.  I painted the units with Krylon silver spray paint.  I like the Krylon paints because they dry quickly and seem to generate less fumes than other brands.

Above.  Inside of 17550 showing transformer and circuit board.  The dimmer switch is located behind the circuit board and can be adjusted by reaching behind the case.

Above- The 20585 showing the original connectors and the transformer and circuit board I added.