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UK Mike (miner2049er)

The Bi-Weekly British Backtrack – MAME Cab Part 3

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So it’s time to move on to one of the most important parts of the build, the Control Panel. Without doubt this is what caused me the most problems. Not only because it has to be right, it is after all the part that everyone sees and uses to interact with the cab, it is how you control not only the games but also the Frontend when launching the games. It could be described as what one might refer to as important.

There are two elements to the control panel, there are the actual buttons, trackballs and joysticks themselves and there is the interface which interprets input from these into something that the computer can understand.

While fitting the monitor was awkward, the Control Panel was just downright annoying if I’m honest and it was made doubly difficult by the fact that it was made of metal. Had it been a wooden panel I would just have taken some measurements from it and built a brand new one, but as you can see here it is a quite complex, moulded unit with a hinge all along its length and lots of extra fixings and fastenings and holes drilled out for the speakers. All of that meant that having a new piece fabricated was out of the question and I would have to work with this one.

The problem was that the cab in its original state had this control layout with just two buttons and a trackball in the middle. When I got the cab it had already been modified and had extra controls added to it such as two more buttons and a joystick. This meant that all the holes drilled in the panel were in the wrong places for my new two player layout and I needed those filling in before putting my own holes in.

I toyed around with different ideas for getting back to a smooth had to go for the only and clean surface to put my own controls into because clearly a new panel was out of the question, a wood panel fastened to the top of the old one would leave exposed edges that would be both ugly and perhaps even sharp, so I decided on the only solution that would really work well and give me a good finish at the end.

I got a friend of mine to weld a plate to the underside of the panel which just left me some holes to fill so I took a trip to Halfords and bought some Davids Isopon P38 (Bondo) which is basically a fibreglass compound that you mix yourself before applying. Be warned though, this stuff really does smell very strong and it should only be done in a well ventilated area, preferably with a respirator, or better still do it outdoors as you can see I did. You mix it and apply it with a plastic spreader and work it into all the areas to be filled and then leave for a couple of days to completely go off and set rock hard.

Once it has set completely it needs to be sanded down before a finish can be applied to it, and the finishes you can apply to it are now a little restricted. The best finish you will get on a panel like this is powder coating which is fine if you are just renovating an original cab and leaving the original controls on, but if you have used fibreglass filler to repair holes then you won’t be able to have it powder coated afterwards, and the only solution is to use paint.

The paint I decided to use was Hammerite which is very resilient, needs no undercoat, can be applied straight to rust and leaves a slightly dimpled finish. This suited my project as there are a couple of dents in it already and I may not get a flawless finish when I sand it, so any imperfections would be glaringly obvious with a smooth, high gloss finish. Happy with my decision though, here is where I made the first of two mistakes on my panel, one quite big one and one small one with annoying and time consuming repercussions.

I put a couple of coats of Hammerite on my panel and got a nice finish that I was happy with then left it to dry for a couple of days. Once dry I marked out the centres for my holes and drilled them out as you can see here. Now I needed to widen these holes out to 28mm to accommodate my buttons and joysticks, and to do it I bought a set of these bits.

The small one did its job really well, the medium one widened the holes a bit more quite easily, but the large one just didn’t make any impression at all. All it succeeded in doing was making the whole panel get hot and force the paint to start bubbling. The bit itself got really hot and a little burned out, so now I was left with a panel with bubbling and burned out paint and with holes too small to use.

That was mistake number one.

The next step was to give the panel back to the fabricator to drill the holes out for me but unfortunately he only had a 26mm drill bit that was suitable, so he drilled the holes out and I then had to use a half round file to open them out to the required 28mm. With that done I had to strip what was left of the paint from it and start all over again, only this time it was a little more tricky getting an even coat while painting around all the holes. Just as I had applied the final few brushstrokes and was trying to move the panel out of the way to dry again, I knocked it over and it hit the floor.

That was mistake number two.

Stuck into my brand new coat of paint was lots of dirt, some bits of fluff and a few chips. Mad at myself I left it to dry overnight and the next day set to work sanding it down for what seemed like the fourteenth time. This time though there were no hiccups (must be something to do with all the practise) and I got a good even coat on at last before it was time for a dry fit and it looked and fitted just great.

I had no such problems with the two coin doors once I had dismantled them but they were made easier by the fact that there was no coin mechanism attached to them any longer. That had long gone. I used the same paint I had used on the control panel and again it gave a good finish because the coin doors already had a dimpled texture to them.

At some point I may pick up a coin mechanism for the cab and fit it but at the moment credits are added using a button on the panel. Time to wire it then.
The emulator M.A.M.E. has a standard set of inputs, for example, pressing [5] will insert a coin (credit), pressing [1] will begin a 1 player game and pressing [2] will begin a two player game. Movement is controlled using the keyboard’s cursor keys, up for up, down for down, left for left and right for right. Fire button 1 is mapped to the [CTRL] key, Fire button 2 to the [Alt] key, Fire button 3 to the [Space Bar] and Fire button 4 to [LSHIFT].

This means that if you run M.A.M.E. on your own PC those are the keys you would use for each game, some games using as many as eight Fire buttons or even two joysticks for a one player game such as Robotron or Battlezone. What we need then is some kind of interface between our arcade controls and our PC inputs, the PS/2 or USB sockets. The way this used to happen is that you would plug your keyboard into the computer but you would hack into it and put simply you would solder a connection between your Player 1 Fire button 1 and the [CTRL] key. Then you would solder a connection between your coin slot and the keyboard [5] key and so on and so on. The problem with this is that it can get very messy very quickly and is ever so slightly annoying if your keyboard breaks.

Enter the I-Pac.

The I-Pac is a small PCB (Printed Circuit Board) which takes the place of the hacked keyboard and sits between your controls and your PC. Each press of a fire button or directional movement on the joystick triggers one of these, a micro switch which is obviously connected to the I-Pac.

If you look at the top right of the I-Pac you will see a connector labelled GND (ground) this must be connected to the bottom contact of each micro switch in the cabinet. It can be daisy chained around each one and does not need returning to the I-Pac. Once that is done, you will see that the next connector is labelled 2RGHT. This must be connected to the right direction micro switch on the Player 2 joystick. The next one is 2LEFT which goes to the left direction micro switch and so on and so on until each control has been connected to the I-Pac. To make swapping parts out later if need be I decided not to solder the connections but to use crimpers and Spade End fittings.

Here is the finished wiring job with the speakers in place and at first glance you can see that it looks a little bit daunting with the number of wires but it really is quite simple to do if you take it a step at a time. Here is the finished panel from above and in the centre you can see the single lit button I have included as a coin insert button. Perhaps on a future project I will use more lit buttons as I think they look very impressive when lit up.

While I may have scrimped and saved a little on my Vinyl finish for the sides I paid a little bit extra for the two joysticks but I'm glad I did now. Joysticks can either be 8-way, 4-way or 2-way. 2-way joysticks only have left and right movement, 4-way joysticks have up, down, left and right movement and 8-way joysticks use diagonal movement too. The joysticks I bought are switchable between 4-way and 8-way depending on the game I'm playing. The reason for that is if you are playing something like Skramble or 1943 then you need the diagonal movement to move freely around the screen, but if you're playing Pacman or Burger Time then you only need 4-way movement. On these games an 8-way can actually cause your character to stop moving as for example both the right and the down micro switch could be pressed at the same time, then the game won't know how to handle the input. What switching to 4-way does is ensures that no two micro switches can be pressed together so the right micro switch will be released a fraction of a second before the down one is pressed and the game will continue as normal allowing you to move in any of the four directions.

Some switchable joysticks are only switchable by reaching through the coin door and activating the mechanism underneath but mine are switchable from above by simply lifting and twisting the joystick until you feel the mechanism switch over. The extra I paid for that ease of switching was well worth it in my opinion, and as a bonus the joysticks have much less "throw" (lateral movement) than others I have tried and they are also magnetically centred when you let go of them. I am more than happy with the extra I paid. They are the Mag Stik Plus from Ultimarc and you can see them .

Now that everything is wired to the I-Pac it is just a matter of plugging in a cable from the I-Pac to the computer using either the PS/2 keyboard port or a USB port. There is also a second keyboard pass through port on the I-Pac which allows you to plug a keyboard in at the same time so that you can configure the PC if necessary without disconnecting anything else or reaching right into the cab.

The last part of the cab to be finished and fitted was the bezel which is the artwork that surrounds the monitor when it is in place. The bezel sits behind the front glass and has a hole cut out where the monitor screen is so that it more or less acts as a frame for the game play area. This also serves to hide the inner workings of the cab which would otherwise be visible through the front glass.

The bezel can take a couple of forms, it can be a fairly sturdy material that supports itself or more often it is a thinner printed film which needs to be supported perhaps between two sheets of glass, or in my case I will sandwich it between the front glass and a sheet of perspex with the same hole cut out of it.

After thinking about a few different designs I opted for this one which is something very basic and classic and is somewhat in keeping with the cab as a whole. I've seen M.A.M.E. cabs that have been plastered with artwork and stickers that are completely out of context and they look ridiculous. I think mine has a much more classic and faithful look about it and I haven't vulgarised my piece of gaming history.

So, that’s it for the hardware build then, anybody interested in the software side of things can check our next blog entry in two weeks time, but if not, then we’ll see you in a month for a look at something slightly unexpected……

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