Wiring Up Your MAME Cabinet's
Coin Door Lights

by Kevin Steele
January, 2004

Introduction

Okay, wiring up your coin doors is not really necessary on a MAME arcade cabinet. You don't have to insert coins to play a game, and therefore don't need to know where to insert said coins. Still, it does add to that "arcade feeling," and what arcade fan doesn't love lots of little lights, blinking or otherwise? A lit coin door is that "finishing touch" that makes a MAME cab look just that little bit more authentic.

So, the next question is how to do it — how do you wire up a coin door? Can you run the lights off your PC? What type of bulb do you need?

Getting Started

This article covers the process of wiring up the "reject button lamps" in a standard Happ Controls coin door (the type that is included with the SlikStik Arcade Machine). Other coin doors may use different sockets and lamps, but the basics are the same.

To begin this project, I first needed to figure out what hardware was already in the coin door:

The Stock Happs Coin Door

Basically, there were two "wedge" type clip-on lamp sockets, each with a 161-type bulb. Some quick online research yielded (at the "lamps, lamps, lamps" page, a good resource for information on arcade machine lamps) yielded the information I needed: the #161 lamp is a 14-volt lamp, and uses a "T3-¼" wedge socket.

#161 Lamp and T3-1/4 Wedge Socket

14 volts is not a perfect match for the 12V available in your PC's power supply, but it's close enough, and running the lamp slightly undervolted won't hurt it (as opposed to overvolting!), although it will be slightly dimmer.

So, the good news was that I had discovered that I could use the lamps that had been included with the coin door — however, I wanted to use LED lamps instead of incandescent lamps - with a rated life of about 50 years, you won't ever need to replace an LED lamp, while the #161 lamp is rated for only about 3,000 hours.

Some more Googling (don't you love how it's now a verb? ;-) and I found some 12V automotive-LED lamps that fit in a T3-¼ wedge socket, at superbrightleds.com. I ordered a variety of colors and sizes (they have 1, 4, or 6-led lamps) to test things out.

Top: #161 Lamp and T 3-1/4 Socket
Bottom (L-R): 4-LED White, 4-LED Ultraviolet, Single LED White, Single LED Red Lamps

Hooking It All Up

Before I could try out my new LED lamps, of course, I had to wire up the sockets and rig up some way to power them. Since the LED lamps were 12V, I could directly power them from the PC power supply, which greatly simplified things.

PC power supplies have a standardized "Molex" power connector. There are four wires in the connector: one red (+5V), one yellow (+12V), and two black (Ground). All I needed to do was to wire up a connector to tap into the 12V line and one of the ground wires.

PC Power Supply Molex Connector Pinout

I've got several large boxes of old computer parts in my shop, so I went "box shopping" and came up with an ideal solution: an old PC 80mm fan, already rigged up with a Molex passthrough connector. The fan is 12V, so I already had the wiring I needed, and all I had to do was cut off the wires from the fan, and connect the wires on the other end to my lamp sockets.

If you don't have the fortune to have an old fan with a molex connector just lying around, you can still buy a molex connector at your local Radio Shack and wire it up. I'm just a fan of "scavenging," and when you've got as many old parts lying around as I do, it pays to dig around first! ;-)

The Sacrificial PC Fan and Closeup of the Molex Connector

I spliced in a 4 foot section of wire to extend the connector (so I could route the power cable inside the PC through an open slot in the back of the computer), and wired up the sockets in parallel, so that if one bulb went it wouldn't cut off power to the other bulb.

Lamps Wired in Parallel

Testing

Once everything was wired up, it was a cinch to install the completed cable into the arcade cabinet. I had already pulled one of the power cables out the back of the computer through an open slot cover, and was using it to power the LEDs that light the trackball on my control panel. I simply unplugged the trackball light, plugged in the new coin door cable, and then plugged the trackball light into the passthrough connector on the coin door cable.

Next, I plugged in two of the white LEDs into the coin door lamp sockets. Unlike incandescent lamps, LED lamps have to be correctly oriented (+/-) or they will not work. Luckily, the only thing that will happen if you reverse an LED lamp is that it won't light - since it's basically a diode (the "D" in LED), it blocks current from flowing in the wrong direction, like all diodes do. Turn the LED lamp around in the socket, and it will light.

The final step was to guide the cable through the cabinet to the coin door, and snap the sockets onto the coin door. Simple. The only thing left was to decide which LED or lamp I thought looked the best.

The Finished Coin Lamp Cable, Installed

The Final Product

I purchased several different LED lamps to try out: A single LED white lamp, 4-LED white lamp, single LED red lamp, and 4-LED ultraviolet lamp. (See the SuperBrightLEDs Review for full details on all the different LED lamps.)

In the end I decided to just use the original #161 lamps, as they had a warm yellow glow and just the right amount of brightness. I may switch back to 4-LED white or 4-LED red lamps in the future, however, once the #161 lamps burn out.

The Glow That Lured A Million Teenagers...

Adding coin door lights is a simple project that does add some "zing" to your arcade cabinet. Like many PC "case mods," lights on a MAME coin door really serve no purpose other than to look cool. Sometimes, though, that's enough.

SuperBright LEDs/Coin Door Wiring Video

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