MAME Diary 006: Dry Fit and Test


This week I’ve been laying a lot of cable in someone’s old box, a phrase often used as a euphemism for something else, sadly not here though.

This week I have actually been laying a lot of cable in someone’s old box.

I also did a lot of screwing too which was nice, but very hard on the knees.

In general a renovated MAME cab will have 4 components that require Mains power and they are the PC, the monitor, the speakers and the marquee light. You could, if you wanted to, use 12 volt speakers and a 12 volt strip light in the marquee and the advantage of that is two fold: (1) You can take a 12 volt feed from the PC itself. (2) Both the speakers and the marquee will only power up when the PC powers up.

If you plan on including fire buttons with lights in then these will also be powered by the PC as the bulbs in them will either be 12 volt or 5 volt. Both of these voltages can be easily found using the Molex connectors on the PSU. The 2 black wires are Negative while the red is 5 volt and the yellow is 12 volt.

My cab has no marquee and my speakers are Mains powered so I will need to power 3 components, and to do that I will fit a four way surge protector inside and leave the cord trailing out of the back to be plugged into a wall socket. Here you can see the surge protector and the lead going through the back of the cab, and here on the left are the components stripped out of the speakers original case to help make the controls easily accessible via the coin door.

Another important issue to bear in mind is that you will have to rewire the PC’s power button so that it is easily accessible and the cab can be turned on without having to reach inside and switch it on. To prevent having to hack apart the original button assembly I came up with an idea to reroute the cable out of an adapted PCI slot cover.

One end will now connect straight to the motherboard connectors so I can just disconnect the original one and leave it untouched, and then on the other end I fitted a Molex Connector enabling me to run the other end to a power button on the cab somewhere. The beauty of this solution is that if I ever need to remove the PC from the cab at some point I can simply disconnect it here and leave all the other circuitry in place. I can also swap the PC for a different one very easily if needs be.

To hold the PC steady and in place in the cab I positioned it how I wanted it and then drew around it with a pencil. Using the lines I screwed some thin wooden lats to the floor of the cab so that the PC wouldn’t move laterally and I then held it down with a ratchet strap.

During the software build undoubtedly the most difficult part was getting the sound to work in DOS, and the most difficult part of the hardware build was the next part, seating the monitor. You can see that the old monitor just sat loose on a shelf and underneath you can see where previous adjustments have been made to the shelf’s height, probably when the original arcade monitor was replaced.

As I was using a different sized monitor I would have to adjust the height again. It wasn’t that fact that it was difficult, it was just awkward having to hold the monitor roughly in place and picture whereabouts the shelf would need to be then temporarily screwing it in place and trying the monitor on it. The idea was to find an optimal height so that when the bezel was fitted, the screen area would occupy a central part of it.

When thinking about fitting a monitor to a MAME cab there are a few things to bear in mind; the main thing is that in general a CRT monitor is the easiest thing to use. A TFT screen is no good for the job at all as arcade cabs had a wide variety of screen resolutions and refresh rates but TFT monitors have a fixed refresh rate. This means that if you play MAME on a TFT screen you will notice graphical glitches and ghosting as the picture is redrawn on screen with the wrong timing. An arcade monitor will give you the best results but (a) you have to get hold of one and (b) you need to buy a specific graphics card to send an output to it A television would give you decent results but again you would need specific outputs on your graphics card for it. You would almost certainly have to decase it to make it fit inside the cab too, and that can kill you. Literally.

Monitors are easily the most dangerous thing inside an arcade cabinet whether it is an original cab or a MAME cab and the monitor can hold a charge anywhere up to 30,000 volts. If you want to work on a monitor like this you will have to discharge it. While it can be done it is not something I will cover here as I have never done it. If you are going to do it you must take great care, for example NEVER go into the back of a monitor with both arms because if you were to get a shock the current would cross your heart, and while that is a great commodity to have in a bra, it is not something considered wise when dealing with massive amounts of electricity, especially if your have wire in your bra.

I will be using a CRT monior in my cab and initially I tried to fit a 19 inch monitor because the more gaming “real estate” you have the better, especially if you are sitting your monitor horizontally. While a horizontal orientation is great for games like Defender, any games that originally had a vertical monitor setup like Pacman will be resized and squashed vertically so you want the biggest monitor you can get away with. Unfortunately due to the construction of my cab I was unable to fit a 19 inch monitor into it. Whenever I had the monitor in I couldn’t get the front glass in place over it, even if I completely decased the monitor it still wouldn’t go in.

Look at the difference between these various cabs and you can see how and where the monitor sits in the various constructions.
Upright Cab with reclined monitor
Cocktail Cab with flat monitor
Solitaire Cab with upright monitor

You can see that with a cocktail cab or a reclined monitor layout there is much more room to accommodate a larger and deeper monitor, but as it was I just didn’t have the space to fit my 19 inch CRT in there so I had to settle for a 17 inch CRT instead. Even that was a bit of tight squeeze as you can see from my modifications to it. I just had to screw a few little extra pieces of timber to the shelf to prop up the monitor so that it would sit both centrally, and at just the right angle so that it’s front edge sits roughly parallel with the front glass when in place.

You can see that the original monitor was a beige one with the front fascia painted black so that it looked better in the cab, but luckily mine was a black Dell monitor so I didn’t need to worry about painting or removing the fascia.

Once all the components had been dry fitted I could test the cab using a keyboard to double check that (a) all the cables were the right length, and (b) the power button on the cab worked to power the machine both on and off.

Now I could remove everything and make all those final finishing touches to the cosmetics without getting dust all over the components and without having to lean in and out of the cab too much when the final finish was on there.

Next time, some final cosmetics.

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