Pac-Man PCB Issues (Noob)

Lucky1

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Hi, I hope someone can help me with my issue... https://youtu.be/iK1bdB5sMYo

I'm new here, well, I've been reading the forum for a while and decided to donate and post.

I bought a Pac-man upright cab with a 60 in 1 jamma board back in Jan '16. I asked the seller for the Pac-man PCB as well. First thing I found out is that the wiring was a TOTAL mess. All the wiring had been cut off and rewired in the same original pac-man 44-pin edge connector to make it fit into a jamma. A nightmare. (The jamma board is powered by a computer-style power supply).

I eventually identified "most" of the wires and installed a new 44-pin edge connector to be able to use the original pcb.

I also bought a Pac-man to jamma adapter to be able to use the 60 in 1 board.
Right now, the joystick and start buttons are working fine and I can play the jamma board without problems. It is set on Free play and powered by the computer power supply. Sound works fine also.

The slam switch, coins, counter, test switch and credit switch are NOT connected to the edge connector. I'm not sure where each goes in the connector. This is more complicated then I thought. (I'm specifying this since it can trigger the watchdog - reset or something else.)


When I first tested the PCB, I checked all the voltages. They are a bit low:
12v --> I have 11.7v
7v --> I have 6.8v

Same readings on the transformer pins and after the fuse block. I changed the fuses but NOT the block since the voltages are the same. But I have a spare one that I can install.

I have read a lot of webpages so far and I'm stuck.
On the PCB:
-Replaced D44VM4 at Q6
-Replaced the 4 pin adjustable voltage regulator at IR1.
-Replaced 6 Rom set
-Inspected all the board for broken traces and rusted legs.
-I have checked many other voltages on the board.

What I have right now is a screen full of green "F" and it seems that the watchdog is resetting the board. We can see a bell appear at some point but that is the only real sprite I can get.

youtube video: https://youtu.be/iK1bdB5sMYo

Any help will be appreciated.

Thanks in advance

Luc
 
Original Pac-Man PCBs are AC-powered, Jamma is DC-powered.

Checked the +5V for the TTLs?
The VCC-Pin of TTLs is always the highest Pin.

The 12V (16V) is used only for Audio-Amp.

Check RAMs and Customchips.
 
Agree - test for +5V DC on the PCB at the ROM chips to make sure that your AC voltage is getting rectified properly to DC. If the readings you gave are DC volts at those points that is enough to make your board run.

Check your VRAM addressor and Sync Bus daughter boards and make sure that they are all installed properly and firmly seated. Press on them when the game is booting and see if that changes anything. Press on the ribbon cable connectors and see if that changes anything. You could have a bad socket or bad cable or bad daughter card.

The pinout for pac-man is here for reference to get your other parts wired. You don't need the slam switch or coin counter wired but you will need the test/service switches at some point.

https://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=pinout&page=Pac.html
I don't know if you know this seller or not but I suspect you were given a non-working PCB.

you probably would have been better off just buying or making a Pac-Man JAMMA adapter.
 
Thanks for your quick replies.

Ok, let's forget about the jamma board. The guy who used to owned this cabinet knew nothing about hardware. He asked is local repair shop to install a jamma 60-1 because his pac-man pcb stopped working...and he wanted more games. I asked for the original Pac-man board and he included it in the deal. I knew it wasn't working.

So, I decided to buy a Pac-man to jamma adapter (see picture) so I can still use the 60in1 board. But, my main goal is to put the cabinet back to it's original setup. I know the jamma is DC powered. I use the pc power supply that you can see in the pic when I plug the jamma board in.

/////

I checked the TTLs, roms and they all indicate ~4.98 VDC.
Except the one at position 3D. (SL74LS75N) ~ 4.37 VDC

It has the Namco custom 284 chip in place instead of the daughter board for the VRAM.
The legs were blackened so I used a file and clean them.

The dip switches are setup correctly according to the manual.

////

As for the pinouts, I have some wires that are not plugged in the connector yet. Some of the wire colors are not matching the Pac-man manual color codes so I have to follow every wire to their parts. I have identified them all but don't know what they are called:

So far, this is what I think they are:

[k]Service Switch = The 2 position black switch
-3 wires: [K]Service, ground and the third is coming from the slam switch I think)

[9]Credit Switch = Red button switch
- 2 wires: [9]Credit and ground

[5] Coin Multiplier PCB = Little board screwed on the inside the cab near the bottom.
- This probably to DC-power the small board

[6]Reset Credit Multiplier = ??? no idea

[8]Coin-2 was rewired as a Free/credit switch installed on the front of the coin door. Right now this "coin-2" wires goes to the Coin multiplier PCB ending up connected with the Coin-1 through that board. I do not know if this was the original setup.

I don't want to get too much into details for the wiring, it can get very confusing and difficult to explain here. I just wanted to know if the fact that some wires are not attached can trigger the board to reset OR the game can still load and be on attract mode without these wires connected.

Any help is appreciated.

Thanks
 

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If the correct voltages reach the Chips, GND is ok, and RGB/sync are attached properly, all other wires are just control and coinage.
The board should work without that.

If the board resets in loop, the watchdog is barking. ;)
Check the rams and the ROM sockets.
 
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Ok, I have something now.
Cleanup and tested the ram pins and sockets. I think one leg was bent.

When the board resets, it sometimes shows "BAD R M 0"

--
Only color is green with some white.

It was resetting when I was pushing UP on the joystick at first. Now, I can play a full game without problem and died at the 1st Bell.

Some parts of the maze show WHITE. That mean all the colors are connected. (I made sure the contact was good between the connector pins and the board edge).

https://youtu.be/YnvzRagjxek
 
If your Pac Man board has not been modified to run on DC, presuming the power supply is correctly wired to the edge connector, your going to have to raise the 5V adjustment (presuming an arcade type switcher), to overcome the losses of pushing DC through the rectifier and regulator circuitry on the Pac-Man PCB. I did this for a friend's Ms. Pac-Man as the original supply was all rusty as sin. So we went the route of a switcher and cranked up the V until the output of the regulator on the Pac-Man PCB didn't go any higher (meaning we overcame the losses).

If you do that, then beware, don't plug the 60-in-1 board back in as the voltage will now be too high.

If you are going to want to be able to switch them you have to make a simple mod to the Pac-Man mainboard to bypass on board rectification and regulation so that your output from the power supply can be 5V.
 
Improvements: Got rid of the Score & Credit displayed vertically on left and right side of the screen. Chip 5M p5 --> solder wasn't clean and was making contact with p4.



Turn up the blue and the red on my monitor and they bleed from the white part of the maze. So it's not a bad wire contact.
 

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Fixes:

1. Video issue: Changed Video Chip 74LS157 at 3B

2. Sound Issue: Changed Sound Amp LM1877 under the heat sink.
 
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