Here is a box of stripped Midway MCR 3 boards. The MCR series hosted a ton of different games. Many of them became classics. There are of course MCR 1,2, and 3 versions. I believe MCR 1 and 2 to be relatively similar in hardware. The MCR 3 is quite a departure with all new board versions. There is some variation within the MCR 3 boards as well.

These boards I’m dealing with have the potential to become classics like Tapper, Spy Hunter, Discs of Tron, and Timber. I can understand some criticism is due from arcade purists. They may think I should not create only partially original arcade boards. These being only partially original because they are in fact original hardware, yet I will being inserting new Roms and making some permanent modifications which may tarnish the real historic value.

My defense is this; I would prefer to introduce some more working MCR 3 boards with classic titles into the quite dried up market, than sell of a bunch of Crater Raiders just to have someone else do the same thing. It is hard to find record of the last time a Tapper board was up for sale. Games like Spy Hunter and Discs of Tron are still seen but not without their large price tag.

Converting MCR boards was also commonplace during the time period these boards were made. I feel like it is less heinous to perform an operation that was performed the same way 30 years ago.

My first challenge was finding the ROM files to make a new Tapper. I always prefer having an example board I can read the ROMs directly off of. I don’t have a Tapper though, so I downloaded the Tapper MAME ROMs off of wowroms.com. Upon opening the folder I realized that the names of the files (FG0, BG1….) had no suggestion of where they actually go on the board. I found some forums where others had reached similar conclusions with no solution.

I remembered when I downloaded the MAME ROMs, I saw there was another version called “Tapper Set 2”. Luckily this ROM set had the board locations included in the naming convention. I made a quick table to match the MAME naming convention to actual board locations.

For the time being I am just doing the cpu and video boards. You can run the game with the sound board disconnected, and that is one less thing I have to worry about. Keep in mind, I don’t really know if these boards work at all. From what I can gather, all of the EPROMs on the boards are 27128, with the exception of the 2764 at 4c. I wanted to avoid using 2764’s because my GQ-4x programmer does not write to them properly. I could have made an adapter but I decided to dust off the EMP-11 programmer along with the Windows XP machine I need to run with off the parallel port. Problem solved.

After hooking everything up I was greeted with the splendid color bar test screen, and finally the Tapper logo. Great! I thought I was all done, but when I started a game I saw that there were problems with the sprites. When the bartender ran to either side, he would turn into three women. A lot of the customers were disfigured as well. Hmm.

I contemplated this for a few days. I tried different boards, different combinations of ROM versions, new ribbon cables. Nothing changed it.

After scouring some online photos and schematics, I found that a jumper on the video board was the culprit. JW1 and JW2 are placed next to eachother, closest to the CP3 marker on the video board.

The example pictured above has no jumpers placed. I theorize the game which took no jumpers is Discs of Tron, since there is only one background throughout the whole game. They may have stored foreground data in the background ROMS, and required a jumper to read the data in to the right buffers for video processing. Through trial and error, I found Tapper to require JW2 to be bridged. After that, I had a functioning board set!