Before we begin with common problems with your PCB (Printed Circuit Board) or in layman’s terms your Pacman board; (This board runs the whole play of the game and it looks like this inside your game.)
MS Pacman PCB
We first need to identify what type of problem your machine is having. Please select from the options below:
- I can hear the sights and sounds of the game, but I can’t see anything on the monitor….Skip to the Pacman Monitor Repair Post.
- When I put my coin in the game; it won’t start when I push the start button. Go to the Arcade Start Button Repair Post.
- My game seems to work just fine but I can’t move my pacman either to the left or right during play; its stuck moving in one direction– or I can’t move it at all…Go to the Pacman Joystick Repair Post.
- My Pacman machine won’t register coins or doesn’t give me credits ..Go to the Arcade Coin Slot Repair Post.
- I have a stand up game but my screen now flips upside down…Un Ground Pin R. Refer to the cocktail table game post.
- My Pacman picture is wavy, distorted, it won’t center, or is rolling across the screen. Go to the Pacman Monitor Repair Post.
- Everything works but I hear no Sounds…Go to the Pacman Sound Repair post.
- My monitor comes on. I can hear the hum and crackle of it warming up, but no game shows on my screen…For this problem it’s more than likely the PCB just isn’t generating the “game” for the monitor to display much like disconecting the DVD player from the TV set. It’s not your monitor’s fault that no picture is getting to it. You will first want to rule out whether you have a bad power supply or a bad PCB board. The PCB’s are usually very reliable and unless wired wrong most often times will work for a long time so let’s lean towards having a bad power supply under this scenario. First, Plug back in your game. If you have a 15amp power supply as explained in Fuse and Power Supply post, then Check to see if the LED light is on.
If not, more than likely you have a bad power supply and will need to order a new one. Since these are realitivley cheap it’s probably a good idea to just go ahead and replace it anyway now to make sure.
Once you have the new one, go to the Installing a 15 amp power supply page in order to see how to install it or to trouble shoot your further. If you still have the old style power supply as mentioned and defined in the power supply section then it’s probably best to bypass this now with the new switching 15 amp power supply in order to get you’re machine up and running again. If you do have the old power supply you may first want to check the fuses that regualte the power +7 volts on the bottom of the game floor beside the main fuses. With game unplugged! Follow the fuse produre in the fuses section to do this, however if the fuses all test good then you have a power supply problem best to just replace it now.
- Everything’s on, but the screen is all scrambled with letters, lines, numbers etc. OK you have a board problem if this happens, but even more specific an Eprom or Rom problem in layman’s terms “a chip” problem, or a bad connection somewhere. At this point if you have this problem you can do one of two things, you can order a new working Pacman or Ms Pacman PCB board and refer to the How to replace a Pacman PCB post.
Info about Pacman’s Eproms And Roms and parts of the Pacman PCB.
Almost all original Pac man boards used masked Roms (9332Bs) that are black, some of the latter Ms Pac Mans had eproms (2532s) with white paper stickers over the windows. The pinouts of the 9332B and 2532 are compatible.
To identify rom chips read the top line of print….”0072-M932D-”
- M932A-39S0 = 6E
- M932B-39S0 = 6F
- M932C-39S0 = 6H
- M932D-39S0 = 6J
- M932E- = 5E
- M932F- = 5F
Note that the letter after 932 is the position indicator.
I am not sure of how to read the second line but you will notice the 9332B, which is a reference to the format of this chip. The 9332 is the equivalent of a 2532.
The second chip (right side) is a EPROM.
Third line is the MIDWAY Copyright (1981) for most Pac Man games (though it was introduced in 1980).
There are 2 color proms that dictate the final color of the maze and character. Pac Man & Ms Pac use the same color proms, other games may vary (see “How many games run on the Pac Man board?).
- 4A PM 1-4 – 256 x 4 PROM (82S126N, 1M 5623, 63S141) Tri State 82S129N will work.
- 7F PM1-1 – 32 x 8 PROM (82S123N, 7603)
Note that these color Proms are only half full of data which is normal and allows for a switchable design if you wanted to make new color proms & toggle the highest address line manually.
Without getting too technical, what you need to know about the chips (Eprom, Roms) is that they can get dirty or become un-seated overtime; or their pins could break or become seated improperly. Sometimes if you’re game is experiencing odd graphics scrambled letters etc…Then the chips are the culprit. You have two options at this point. Take the whole PCB out and simply buy a new one and plug it back in.
Or, You can try to clean and re-seat each of the eprom chips. To try this follow the procedure below:
First— what you need to do, is to take the PCB out of the game. To do this, Unplug the game first. Then find the PCB in your game. Unhook the wiring harness that connects the game and then locate the screws if any that are holding the board to the wall. When found unscrew the bolts (screws) holding the board in place and remove it intact and lay it flat on a table. Make sure if you have a MS Pacman board that you keep the daughter boards in tact as well.
Second— Take a flat head screw driver and begin with chip 6F. Or you can use a IC Chip Tool to lift the Eprom.
Gently slide the screw driver between the Eprom and it’s seat and gently pry up.(Be very careful not to bend the pins!!!!) Lift on one side (south side) then go to the top side (north side) of the chip until it comes loose from its seat at the same time.
Third–Now inspect the chip looking for dirt, bent or broken pins etc. If you see that it is dirty with the end of a pencil eraser and with your finger behind the pins gently rub the eraser over the pins to remove the dirt and grime.
Fourth…Once the chip is clean then re-seat the chip back into its socket. Be Very careful not to bend or break the pins trying to get the chip back in the seat. Also make sure ALL the pins are connected and slid back down in their seat and didn’t bend underneath. Check this by inspecting every pin placement making sure they are all seated.
Fifth–Now go to the next chip and repeat the same procedure until you get all the chips cleaned that can be unseated.
Sixth–Now plug the PCB back in the game a re-try. If the scrambling is gone congrats you’ve fix it. If not re-inspect that there are not other Eproms or Roms that you might still need to try to clean or fix. Also check in the advance troubleshooting post for further fixes.
Replacement rom sets are available online. (Where to buy a Pacman Speed up chip click here) You may want to order these first as a cheap try before buying a new PCB.
Multi Pac Items And Cheats
Several PCB Multi Pac Kits were developed and became popular through out the late 90’s and 2000’s. Among the best of these were the Clay Cowgill Multi Pac kit and the Super ABC Two Bit score kit. These kits plugged into an original Pacman or Ms Pac man PCB and allowed multiple pacman games to be played off 1 PCB board. Also allowing the player to continue where last died and save the high scores of the game through unplugging. They are becoming very rare but I still see a few land on Ebay every now and again.