Baby Pac-Man
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1 Introduction
Baby Pacman (Also: Baby Pacman) was produced in 1982 by Bally. Baby Pacman is one of the few hybrid video/pinball games that were ever produced, and only one of two hybrid games produced by Bally.
2 Technical Info
2.1 System Overview
2.2 Boards
2.2.1 MPU
This game uses a Bally AS-2518-133 MPU. This is nearly identical to the AS-2518-35 board, with a few minor differences. A -35 board can be converted to a -133 board and vice-versa by swapping a few through-hole components. See the notes on this conversion process on the main Bally/Stern page.
This game uses two ROMs. A 2732 eprom at U6 and a 2532 eprom at U2. The MPU board can be re-jumpered to accept two 2732 eproms.
The diagnostic LED flash sequence is slightly different on the -133 board than the -35 board. The -133 board's diagnostic LED displays 6 flashes, while the -35 board displays 7 flashes. (TODO: Include reason for this difference) Otherwise, troubleshooting procedures are identical to that of the -35 board.
2.2.2 Driver/Lamp
This game uses a Bally AS-2518-107 combo board to drive both the feature lamps and the solenoids. This board is also found in Bally's second hybrid game, [Granny and the Gators http://www.ipdb.org/machine.cgi?id=1083].
Each SCR in the lower left area of the board (marked as Q1 through Q28) is responsible for driving two lamps. If one of the SCR's fails, usually a pair of lamps won't respond and will either be stuck either on or off.
2.2.3 Vidiot
This game uses a Bally AS-2518-121 Video board to display output on the monitor, output sound, and receive input from the control board's joystick and buttons. Because this board is reasonably complex and unique, it can be a central point of failure in this game. A modified version of this board named the "Vidiot Deluxe" board was used in Bally's second hybrid game, [Granny and the Gators http://www.ipdb.org/machine.cgi?id=1083]. The two boards are different enough to not be cross-compatible.
Four 2764 eproms are used for the video section of the vidiot board at U9-U12. The sound section of the board uses one 2764 eprom at U29.
2.2.4 Rectifier
This game uses a standard Bally AS-2518-132 rectifier board.
Since this game does not use any score displays (like normally found on a pinball machine), the +230VDC (190VDC unregulated) found at TP2 is not used. This means that it is not necessary to install a fuse at F2.
The -132 board is very similar to an AS-2518-54 rectifier board, but with a few modifications/improvements. The -132 board uses 6 amp diodes at CR5 through CR8, while the -54 board uses 3 amp diodes. The 6 amp diodes provide better heat dissipation. The -132 board uses two circuits for the general illumination, and thus also uses two separate fuses (found at F5 and F6). This allows for more lamps by spreading the load between two circuits. The early revision of -54 board only uses one circuit and one fuse, however, AS-2518-54 revision B includes two circuits and two fuses for the general illumination.
The Fuse values differ between the -132 and -54 boards.
2.3 Monitor
This game uses a 13" video game monitor mounted vertically.
(TODO: include more details about the monitor and possible replacement options)
2.4 Speakers
This game uses two oval 3"x6" (TODO: Verify measurements) 4 Watt 4 ohm speakers in mono, which are mounted above the coin door on the inside of the cabinet. If necessary, a single 4 Watt 8 ohm speaker can be used (Note: Do *not* use two 8 ohm speakers!)
2.5 Playfield
Baby Pacman has two distinct types of playfields. An earlier version of the playfield uses a matrix of lamp sockets for the feature lamps. A later version of the playfield uses a circuit board with twist-on sockets. The version with the lamp sockets was considered to be difficult to work on and prone to shorting out bulbs in the sockets or SCRs on the driver board.
The two different playfields appear to use different connectors, so it may not match up with the connector found in the cabinet. A pigtail adapter might be needed to adapt the playflield connector to the cabinet connector if one type of playfield is being swapped in for another.
2.6 Fluorescent Lamp
This game uses a fluorescent lamp behind the marquee, which is connected directly to the transformer.
(TODO: Include what type and size of lamp)
3 Problems and Fixes
3.1 Connectors
The IDC connectors in this machine are a weak link. They were a cost-cutting measure when these machines were originally built, and as a result, often fail and need to be re-pinned because either the wire pops out of the pin in the connector, or the connector pin gets too loose and can't make contact with the header pins. This can be a source of many problems. It can sometimes appear as a consistent discontinuity issue, an intermittent issue as the machine moves/vibrates, or as heat causes things to expand and possibly loose contact. It is a good idea to replace any problematic IDC connectors with molex KK-series connectors. Some individuals recommend only replacing the connectors with problems to save some time, while others recommend just replacing them all at once in order to avoid potential future issues with the IDC connectors.
The connectors can be purchased from Great Plains Electronics and Big Daddy Enterprises. The 0.100" 25-pin and 28-pin connectors have been discontinued, so they may be difficult to obtain. If necessary, two smaller connectors can be used side-by-side in place of the larger 25 or 28-pin connectors.
When re-pinning the connectors, note that there are a few pins that have two wires connected to a single pin on the MPU board's J2 connector and the Vidiot board's J8 connector. The wiring for all the connector pins can be found on page 38 in the manual on the diagram labeled "Wiring Diagram Video-Pin Cabinet".
Baby Pacman uses both 0.100" header pins and 0.156" header pins. Here is a list of all the connectors found on the circuit boards:
| Board | Connector | Pins | Pin Size |
|---|---|---|---|
| MPU | J1 | 28 | 0.100" |
| MPU | J2 | 15 | 0.100" |
| MPU | J3 | 16 | 0.100" |
| MPU | J4 | 19 | 0.100" |
| Driver | J1 | 15 | 0.100" |
| Driver | J2 | 12 | 0.100" |
| Driver | J3 | 15 | 0.100" |
| Driver | J4 | 10 | 0.156" |
| Driver | J5 | 6 | 0.156" |
| Driver | J6 | 12 | 0.156" |
| Driver | J7 | 6 | 0.156" |
| Driver | J8 | 25 | 0.100" |
| Driver | J9 | 10 | 0.100" |
| Driver | J10 | 6 | 0.156" |
| Driver | J11 | 6 | 0.156" |
| Vidiot | J1 | 28 | 0.100" |
| Vidiot | J2 | 20 | 0.100" |
| Vidiot | J3 | 12 | 0.156" |
| Vidiot | J4 | 12 | 0.156" |
| Vidiot | J5 | 2 | 0.156" |
3.2 Monitor
3.3 Vidiot Board
3.4 Game Does Not Eject Ball on Button Press in Pinball Mode
The right flipper is responsible for ejecting the ball during pinball mode. If the button is not working correctly or if the player does not press it, the ball ejects automatically after a few seconds. If the player presses the right flipper button and nothing happens, that may indicate that there is something wired incorrectly or that the diode is missing on the right flipper coil lugs. The right flipper is different from the left flipper since it is responsible for responding to the player to eject the ball in pinball mode.
3.5 Game Randomly Exits Pinball Mode
There is a known issue where the game will appear to exit pinball mode at random (before the ball drains or lands in a saucer) and re-enters video game mode. That may indicate that the diode is reversed on the right flipper coil lugs. The right flipper is different from the left flipper since it is responsible for responding to the player to eject the ball in pinball mode.
Also see the Pinside discussion thread on this issue.
4 Paperwork
Manuals, schematics, coin cards...
5 Rubber Rings
Rubber Ring Sizes goes here
6 Photos
Teardown photos go here
7 Repair Logs
Did you do a repair? Log it here as a possible solution for others.