Newbies still have lots of trouble with the types of lamps used to light up coin windows & such, along with the voltage that is used to power them, so I'm going to move & combine different sections from my Help Pages into a single help doc linked to the lamp section of the Parts Page.
This is not a technical doc, but rather just a basic description of the common lamps used in coin-op. Many newbies want to know which lamp will last longer, what amps it will draw & so on. If you had a few hundred games on the street operating 24/7 I could possibly see the relevance of this, but as hobbyist I cannot see justification with a fifteen cent lamp that may last longer than the game in home use, although, I realize that some collectors own more games than operators do :-() In any event, the sole purpose of this is to help you ID a lamp type & voltage for your particular game.
First the bayonet type is a lamp with a smooth cylinder base that has two projecting pins which fit into slots on the holder & when twisted a quarter turn, lock themselves into the socket. Bayonet lamps would be #44 or #47 when used in a 5 to 6VDC or 6.3VAC circuit, and when powered by 12 volts you'd need a lamp such as the #1813.
The wedge type is as implied, a wedge lamp is pushed straight into the socket & has a chisel-shaped base, as opposed to, the cylindrical bayonet type. One loop of exposed wire to either side of the wedge base makes contact in the socket. Wedge lamps used in a 5 to 6VDC or 6.3VAC circuit would be #555 & in a 12 volt circuit you'd need #161 lamps.
As for voltage supplied in your particular cab, even if there are no lamps in it & you have no manual or schematics, you can always measure the voltage right across the two wires that feed the lamp... right at the socket. If you own a game you should have a meter, but on the off chance that you don't, any meter should do the trick, even a small pocket-sized $5 analog meter from your local electronics store or I have them on the Parts Page if you're ordering other parts. If you don't get a reading on DC swap over to AC because cabs are powered by both AC & DC voltages.
If you find your sockets are shot & you cannot find new like ones, but can find ones that are the same, but use a different based lamp, you can change over to them & select the appropriate lamp for your supply voltage.
One FAQ that seems unending is why are they called "lamps" instead of "bulbs". A bulb is defined by Webster's as, "1. any round, enlarged part, esp. at the end of a cylindrical object: the bulb of a thermometer 2. the round glass housing, in which a partial vacuum has been established, that contains the filament of an incandescent lamp". Household incandescent lamps of yesteryear were always in the shape of a bulb, hence earning the name of "light bulb", which has stuck even though we have a huge variety of household lamps today in every shape imaginable... they are still light bulbs. Our industry has called a lamp a lamp for as far back as I can remember & never adopted the term "bulb" and that may be because lamps that we use are not always in the shape of a bulb, rather then the loose meaning of a bulb being just a part of a lamp. Most people today have come to know the term "lamp" as only the thing that sits on either side of the sofa, but a lamp is any device that gives off artificial light.
Happy Gaming....