The following is for informational purposes only. No responsibility is assumed for its use. In using AC, there is an electrocution hazard. Grounding precautions should be taken. (The equipment has metal cases). Also, parts should be selected that can safely handle the current. Fuses should be utilized to protect the equipment as well as to prevent fire hazards.
30 volt Locomotive Bulbs:
Perhaps the best solution to this is to obtain the 240/120 step-up/step-down transformers. The factors involved in selecting a suitable transformer(s) are the amperage, the voltage, the design (whether isolation of AC supply is provided (primary-secondary isolated) or if an autotransformer is used). The lamps determine the current or power requirement of the transformers. The 200 watt locomotive bulbs will need 7 amps for sustained lighting. A nice advantage of running the bulbs on AC is that a diode (having proper current and voltage specs.) can be switched into the circuit to accomplish dimming - thereby eliminating a need for a resistor(s). This will not give the dimming setting of a locomotive headlight (15 volts). It would be a voltage equivalent of 21 volts.
In a series arrangement, 120 volts is connected to the 240 side of the transformer to obtain 60 volts (dual bulbs in series). If 30 volts is desired, the 60 volt output may be connected to the 240 side of a second transformer.
The "Electrical Aspects" page indicates that the preferred method of wiring of dual clear bulbs -- is in parallel. Doing so involves finding a high amperage 30 volt source (7 amps per bulb with allowance for cold start).
If one can't find a 30 volt transformer with enough current output, 2 of the 240/120 volt transformers could be used where the output of the first transformer (120 volts 60 volts AC) is the input to the second transformer to yield 30 volts (60 volts to 30 volts AC).
In order to obtain the required current output, the transformers can be connected in parallel. If an autotransformer(s) is used, one must keep in mind that there is a shock hazard involved. The autotransformer is merely a tapped inductance. (120VAC input into a continuous coil, tapped for desired output voltage(s)). There is no isolation from the ground. For safety, a ground fault outlet should be considered.
75 volt Locomotive Bulbs:
If it is desired to use the new 75 volt bulbs, 3 24 volt transformers in series could be used (using transformers with sufficient current ratings). The transformers should all be identical (design aspects of the transformers are such that they should be identical for maximum efficiency).
I have found that two 36 volt transformers (in series) or three 24 volt transformers (in series) connected to a full wave bridge rectifier will perform adequately. As for the current needed, I measured 0.34 amps on continuously operating a 20585 Gyralite motor. It would be desirable, however, to have a reserve capacity for starting as well as combating any resistances to the mechanism (grease buildup, bearing wear, etc.).
The 74 volt motors will also run on 60 volts DC (using a full wave bridge with 60 volt AC input).
I have found that a 28 volt transformer works adequately for the 32 volt motors, again using a full wave bridge rectifier. If the motor is rated 32 volts and the bulb transformer (above) output voltage to the bulb is 30 volts, a full wave bridge rectifier may be used to supply the motor from the bulb transformer output
It is also desired to use fuses in all supplying lines to the locomotive accessories in order to prevent damage to the equipment (blockage in mechanism or short circuit).
Any switches as well as wiring must be capable of handling the currents in the accessory being powered.
Values of diode (dimming) as well as the full wave bridge rectifier should have "reserve" in the current-voltage design of the power supply.