This page deals with the most common complaint in the Pac-man cabinet. It effects all models and usually has all of these symptoms:

1. The game won't always start up when plugged in and randomly crashes in the middle of a game.

2. There is a distortion line (Hum bar) which scrolls across the screen from right to left about once per second.

3. a LOUD HUM is coming from the speaker.

Click here to listen to the HUM.


There is a continuity break in one of the four wires which carry AC power from the transformer on the floor of the cabinet, through the fuse block, through the wiring harness, through the edge connectors, and onto the game board.

PacMan (and the electrically identical Ms.Pac-man) cabinets were the first mass produced video games and they used a multi-tapped transformer to provide two different AC voltages to the game board, 7 and 14 volts AC. On the game board, there are two separate power supplies. The first turns the 7 VAC into well-regulated 5 volts DC for the logic circuits. The second is a crude half-wave rectifier which changes the 14 VAC into unregulated 12 volts DC for the audio amplifier.

Because the two power supplies are drawing off of a common transformer which is center-tapped to ground, all four legs of the AC must be connected. If not, the 60 cycle AC fluctuations get past the 5 volt regulator and can be seen on the video screen as the HUM BAR wave.

Also, the Audio amp picks up the AC coming in on the 12 volt supply line and amplifies it as a 60 cycle hum.



There's 110 volts AC on the primary side of the transformer; It'll bite you if you're not careful. So before you stick your fingers in there, UNPLUG THE GAME. 'Nuff said...


Pull the four fuses and throw them away. Replace them with four nice new shiny ones. Fuses get brittle over time and they can become intermittent. Every operator has stories of how games worked fine in the shop, but when they were delivered to the location the fuses were mysteriously 'blown'.

While you have the fuses out, inspect the fuse holders. If there is any evidence of soda or beer slime, clean the metal clips. Before you pop your new fuses in, squeeze the clips together slightly to put some spring tension back in them.

If the fuse holder clips are tarnished, corroded, slimy with Coca-cola or if they don't have any spring tension left in them, order the FUSE KIT below which consists of NEW fuse holders and fuses.

The game came from the factory with a filter card between the wiring harness and the main game board. This board was installed in order to pass the FCC's RF Interference requirements. Without the filter board installed, the Radio Frequencies produced on the game board would sneak back down the line cord, causing all of the AM radios in the area to 'buzz'. Since this is no longer a problem, we recommend that if it hasn't already been removed, you toss the filter board over your shoulder and make a wish.

The filter board is not necessary and just adds one more set of contacts for our four power wires to pass through.

This next step will require you to be able to see the video screen at the same time as you can reach the game board. Either find a mirror or someone to assist you. Plug the game into the wall and give it a minute to warm up.

Grab the main connector where it meets the top of the game board. Gently flex the connector back and forth while you or your assistant watch the screen. If the picture suddenly straightens up while you are putting pressure on the connector, you have located your bad connection.

Unplug the connector and inspect the game board for burned traces at the edge connector. Pay close attention to the heavy connections at each end of the connector on both the front and the back of the board.

If there are burned traces, you may want to consider sending us the game board for a free checkup.

For the do-it-yourselfer, we sell the PAC-MEND kit which replaces both the connector on your game board and the one at the end of the wiring harness.

You can order the kit on-line below.

Part number Description price comments location Open a picture
in a new window
Edge connector repair kit
$39. for the main board and the cabinet wiring harness connectors edge connectors
FUSEKITRepair kit includes new fuse holders and fuses for all models of BALLY / MIDWAY video games. $29.Both primary and secondary fuse holders
(2) 1 amp fast-blow
(3) 2 amp slow-blow
(2) 5 amp normal-blow fuses
instructions, repair tips and diagrams
PAC-MAN, MsPAC-MAN and other Bally/midway video games.


4418 Pack Saddle Pass
Austin, TX 78745
512-447-8888 Voice
512-447-8895 Fax

e-mail to: Sales@Twobits.com