The single ♫ PROM function
2764 for MA-216 sounds board
Installation of an high capacity PROM on sound boards.
Interest and use
In addition to improved reliability and reduced consumption (use of a single circuit instead of two), the extension of the memory space allows certain changes, for example:
- Have two sets of voice (French/English selectable)
- Add the voice on a flipper which do not have
- Improve the self-test program
The module plugs on the location PROM1 (U5). In this photo, we use a simple EPROM replacement for the Goin' Nuts (682). We recommend the use of EEPROM 28C64, more flexible employment and lower consumption.
Modes of operation
The adapter can be used in three different modes:
- Simple mode - the 28C64 replaced a couple of 2716.
- Dual mode - the 28C64 replaces a doublet of 2732 (with possible selection).
- Extended mode - completeness of the 28C64 is used.
The mode of operation is determined by the position of the E4/5/6 straps, E7/8/9 and E13/14/15.
For first generation boards (B-20887-1), an additional amendment is to correct a bug in the circuit. Indeed, the E5 point is not connected to AB11 (as indicated on the diagram) and shall be connected by a wire.
To make the adapter, you need:
Tulip socket 28 pins.
A barette scored (2 x 12 pins).
A 4.7 KΩ resistor.
A printed circuit board.
Start with welding resistance (the components). It then welded copper side barettes.
To facilitate this operation, can preload the pins on the array with a bit of welding.
It will ensure that the array doesn't exceed the side components. Finally, it remains more to solder the support components side (over the resistor).
Single PROM ♫ adapter can be installed on the SYSTEM 80 and 80A equipped with a B-20887 board. For example: March, Volcano, Black Hole (US), Haunted House, Devil's Dare, Caveman, Goin' Nuts, QBert Quest, Rocky, Spirit, Krull, Super Orbit, Royal Flush Deluxe.
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