NAMCO Pac-Man Video Arcade

Repairs, Restorations, Tweaks and Insights


July 25, 2020

Pac-Man is easily one of the most iconic 1980s arcade games and characters. The game and its impact has proven to be timeless. Pac-Man is still well known in 2020, 40 years after release, and the original Pac-Man arcade has been ported to just about everything.

Generally I don't try to collect arcade games that are commonly emulated well, whether it's on MAME or a release for the iPhone or some console system. This is why I typically collect pinball machines or vector arcade games. There are no hard rules, however, and I decided to pick up an original Pac-Man cabaret. Here are a couple items I considered:

Pac-Man Cabaret (Mini)

July 25, 2020

Classic arcade games often came in 3 cabinets: Full sized, Cabaret (Mini) and Cocktail. The full sized cabinets are likely the ones that people think of when arcade games come to mind. The cocktail cabinet may have been experienced at restaurants and bars, often around the waiting area (or some corner). While one stands to play the full sized cabinet, one typically sits when playing a cocktail. Note, however, that some cocktails can be raised up to standing height.

The cabaret (or mini) cabinet was less common in my experience (I don't have numbers to back this up, just what I recall). While the cabaret is still played standing up, the cabinet is much smaller and much less imposing. Both the cabaret and cocktail versions typically did not have artwork on the sides, making it stand out less. The cabaret cabinet is often wood grain.

Below is a picture of the Pac-Man cabaret (Mini) cabinet.

Below is a picture of some paperwork stapled inside the cabinet. It indicates this cabinet is a "Mini".

Namco Pac-Man? Midway Pac-Man? Which is it?

July 25, 2020

The plaque on the back of Pac-Man cabaret does a good job of telling the story. Quite briefly:

A picture of the plaque is shown below.

As a quick side note, the relationship between Namco and Midway gets murkier with Ms. Pac-Man and Pac-Plan Plus. Generally speaking, Namco did not employ the developers that modified the original Pac-Man code and hardware to create these derivative works. Ms. Pac-Man was the result of work by General Computer Corporation, which eventually worked out licensing with Midway and Namco. The origin of Pac-Man Plus is less well known to me, but I believe Midway worked with the developer and the licensing with Namco is unclear or never happened.

How Pac-Man got his name

July 25, 2020

The story goes that the original name given to Pac-Man in Japan was Puck-Man. However, there was concern that in the United States vandals might change the "P" an "F" and no one wanted the game's artworking showing "F*ck-Man". Eventually Puck-Man was adjusted to be Pac-Man.

Even during manufacturing there was confusion regarding the naming. The PCBs that run Pac-Man have material that says "Pack-Man" (with the "k"). This is shown below.

Pac-Man Main Board

July 25, 2020

If you've ever wanted to see a picture of the original hardware that runs Pac-Man, look no further than the picture below.

Pac-Man, Ms. Pac-Man, Pac-Man Plus and Pengo!

July 25, 2020

Knowing that a high quality multi-pac kit existed was one of the reasons I decided to purchase an original Pac-Man. There are a few different multi-kits available but I went with the "High Score Save" version. In my mind, the key attributes of this kit are:

In addition to the items above, the kit allows playing of Pac-Man Plus and Pengo. That is just an added bonus.

I did come across some unadvertised negative behavior of the High Score Save Multigame kit:

From a purest point of view, it is rather disappointing that High Score Save Pac-Man multi-kit removes features. However, one can argue that no purest would install a multigame kit in the first place.

Generally speaking, the multi-Pac kit works by replacing the existing ROMs with more advanced ones that can be told to select their content at runtime. This works because these games (Pac-Man, Ms. Pac-Man, etc.) all run on the same hardware. There is more complexity, however, because the "High Score Save" kit also allows Pac-Man high scores to be saved across power on/off and initials to be entered. This does mean the ROM code has been modified, but none of the code used during game play has been changed.

Below is a picture of how the kit arrived once it was removed from the packaging.

As mentioned, installation of the kit involves removing several socketed chips and replacing them with the High Score Save variant. These new chips are actually little PCBs that are daisy chained together with a small cable. This cable allows the multi-Pac kit to select the appropriate data for the active game. Additionally, there is a new board that provides the High Score Save functionality and, to the best of my knowledge, controls the selection of chip data. Below is a picture of the multi-Pac kit installed.

Even though I was very careful during the install, I ended up having two problems. At first boot after installing the kit, my Pac-Man cabaret displayed what is shown below!

After some failed attempts to fix the problem, I decided to start removing the High Score Save multi-kit. While removing the board that installs at the "sync bus" socket, I found that one of the pins had become bent.

TBD: Insert image of Sync Bus board.

I straightened out this pin, plugged everything back in and... got the following.

Big improvement but still not quite right. After doing some additional debug, I realized that the problem would go away if I tapped the color tables chip at 4A. I reseated this chip and got a beautiful working Multi-Pac. Below is a picture of the first time I selected Ms. Pac-Man.

Pac-Man Test / Diagnostics Did Not Work

July 29, 2020

While I didn't know it when I purchased my Pac-Man cabaret, I realized shortly after that I could not enter the diagnostics. Pac-Man cabaret has a small switch just inside the coin door and to the right. In one position the game runs normally while in the other, the game enters diagnostics. At least in theory because, on my game, it always stayed in game mode.

I started by looking at the schematic and realized the test switch was tightly tied to the slam tilt functionality. Take a look at the schematic below (which is taken from the Pac-Man manual).

While the main PCB schematic is not shown, the main PCB is providing 5v by way of a pull-up resistor. If this stays 5v then the main board runs in regular game mode. However, this line is connected to ground if the switch activates. There is another way this line can be brought to ground: when the slam tilt is activated. Apparently the software in Pac-Man treats a "long term" ground as diagnostics and a short term ground as slam tilt.

Around this time, my High Score Save multi-pac kit arrived. I decided to install it prior to determining why my Pac-Man cabaret would not enter diags. After it was installed, I started looking into this problem again.

I used my digital volt meter and showed everything was connected well, but found the switch itself was bad. The original switch is no longer available, so I replaced it with a readily available STDP switch.

I traced the diag/slam tilt signal back onto the Pac-Man main PCB. The signal eventually ends up at a 74LS367 hex buffer. This buffer allows the signal to be multiplexed on the data bus (data bus 4 to be specific). By this I mean that DB4 contains a different signal at different times. It can have any of the following meanings:

The game enables the output of the appropriate 74LS367 and, by doing this, knows the meaning of DB4. For example, if it enables the 74LS3367 at 8H then DB4 will have Diags/Slam tilt. If it enables the 74LS367 at 8D then Db4 will have the DIP switch 5 setting. The game's programming will never enable these at the same time.

It's difficult to test data bus lines with just a digital volt meter. This is because the output pin is only valid when that 74LS367 is enabled. A logic analyzer is scope is appropriate here since you need to say "show me this value only under this condition". I wasn't motivated to pull out my scope at the time so I simply decided to purchase some 74LS367 chips. I was pretty confident one was bad so I'd replace the existing ones. Below is a picture of the 74LS367 at 8H.

However, I never replaced any of the 74LS367 chips. While waiting for the chips to arrive, I reached out to High Score Save and asked whether their kit impacted the diagnostics functionality and the slam tilt functionality. To my surprise, and disappointment, they confirmed that the kit removes both the diagnostic functionality and the slam tilt functionality! Yes, I realize there's a trade off here.

At this point I decided to postpone any further work on this problem. I may have 100% fixed the problem by replacing the switch, but was unable to test it because I had installed the High Score Save Multi-Pac kit at that time and, with that installed, there is no way for me to test without removing the kit.

Pac-Man Monitor

July 25, 2020

TBD topics to include. G07 FBO 13". B&K 467. Rejuvination. Clean/Balance. B+ voltage. 120v. CR-28 adaptor.

Pac-Man Marquee Lighting

July 25, 2020

Credit Multiplier

July 25, 2020