I am currently working with IHC Smoothside passenger cars, interiors, and lighting kits and I would like to wire in an appropriate capacitor to eliminate flickering.
Does anyone have any suggestions as to size and type of capacitor to use?
It should be a non-polarized electrolytic capacitor of at least 50 Volts rating at the highest microfarad you can squeeze into the available space, without being obvious.
Non-polarized electrolytics are sometimes hard to find, so I sometimes use a small bridge rectifier so a normal polarized electrolytic can be used.
One source of non-polarized electrolytics is All Electronics in Van Nuys, California; but unless you intend to order several other items the postage can be a killer ($7.00 minimum).
I doubt if Radio Shack carries such items, since they seem to be getting away from electronics components and stocking only fast-selling cell phones and similar gadgets.
A disc ceramic capacitor is smaller, but won’t hold a charge long enough for use in lighting circuits.
Is this DC or DCC? DC: the above suggestion is good. DCC: I think you will be forced to build a power supply in the coach. A diode or diode bridge to create single-polarity power, a capacitor to take out the ripple, and probably a resistor to limit inrush. The starting point for the design would be the amount of current the lamps will take.