Quoted from pinrepair.
In the three first System1 games there was a three tone chime unit, as used in Gottlieb's EM games. With Close Encounters this changed to a simple tone generator sound board, which still used the same three driver board transistors to generate sound. This sounds board was located in the lower cabinet right next to the knocker (where the chime box was previously mounted).
Sound improvement came with Totem, when a microprocessor controlled sound board replaced the earlier 3-tone sound board. Both the chime box or the sound boards were located in the same place, in the right side of lower cabinet. The new sound board as used on Totem and later games (multi-mode sound), though having more sound bites, was not really a big sound improvement for the System1. It had a switch that changed the sound format, much like Williams did. It also used a now unavailable Rockwell chip R3272-12. It still used the same three drivers transistors from the driver board, but not in unison (as Williams and Bally did to control more than three different tones). Instead Gottlieb's MPU controlled sound board randomly picked the different sounds to play. This caused some player confusion, because a 10 point switch could have any number of different sounds.
Gen2 Sound board Ground Problems.
The +5 volts for the second generation sound board comes from an onboard 7805 regulator (center top of board) on games Totem and later. The ground connection is from two zinc plated mounting screws. These screws can corrode, causing the ground connection to be intermittent. Worse, the regulator output voltage can rise to +12 volts because of this bad ground. This can of course ruin the logic chips, and often the 6530 RIOT chip. The 6530 RIOT (RAM, input, output, timing) chip is no longer available and very hard and to find and expensive. And since the 6530 contains masked ROM code, it is unique for this board.
So it is important to check and clean the 7805 regulator mounting hardware. Put some grease on the surfaces before reassembling, to prevent moisture causing any corrosion and blowing up the hard to get parts.
Substituting Chimes for the Sound Card.
Because of the sound card problems listed above, many operators take out the MPU controlled sound board and replacing it with an older chime unit. Most players find this far more pleasing and consistent to the ear. All system1 games are downward compatible to chime coils. Be sure to use chime coils 12 ohms or greater. If coils with less resistance than 12 ohms are used, the driver board transistors Q26,Q27,Q28 will fail. If adapting a chime box from a Bally game, that should work fine as 50 volt chime coils will have higher resistance. Also don't forget to add 1N4004 diodes to the chime coil lugs, with the coil's power lug connecting to the banded side of the diode.
Mount the chime box right next to the knocker coil in the lower cabinet side panel near the game's power switch.
Route the 25 volt power from the adjacent knocker coil lug (banded diode lug), which is right next to the existing sound board (and the newly mounted chime box).
"Daisy chain" the 25 volt DC coil power to all three chime coils' banded diode coil lugs.
Now move the following wires from the sound board connector to the chime box coils' non-banded diode coil lugs:
orange/black/black wire goes to the 10 point chime coil lug.
red/brown/yellow wire goes to the 100 point chime coil lug.
red/green/green wire goes to the 1000 point chime coil lug.
Remove the sound board from the game.
Providence, RI
