June 3, 1997 by cfh@provide.net This document covers the following hacks:
Click here for a 39k ZIP file of all the ROM images needed for the following conversions. This include two different versions of Galaxian, the graphics ROM images at 1H and 1K, and the color PROM 32x8 BiPolar 82S123 at location 6L. These images are thanks to Patrick Peters. Note the combination ROM files were created by concatenating the original ROM files using the following MSDOS copy command with the "/b" parameter: copy /b rom1+rom2+rom3+rom4+rom5 allroms
Galaxian Single 27128 EPROM
Modification This document describes how to take a Midway Galaxian PCB (printed circuitry board) and modify it to use a single 27128 EPROM instead of five 2716 EPROMs that live on the satellite PCB. This should increase the reliability of the PCB as there are fewer chips, and the satellite board can be discarded. Necessary equipment:
PCB Modification steps.
Galaxian ROM code explained.
$0000 - 07FF Galaxian 7U $0800 - 0FFF Galaxian 7V $1000 - 17FF Galaxian 7W $1800 - 1FFF Galaxian 7Y $2000 - 27FF Galaxian 7Z $2800 - 2FFF Galaxian 7W (filler) $3000 - 37FF Galaxian 7Y (filler) $3800 - 3FFF Galaxian 7Z (filler) This is 16384 bytes, or 16K. You need a 27128 EPROM for this. You'll notice that I've duplicated certain ROMs in some blocks of memory, like in $2800 - 3FFF. I don't know if this is necessary. I had to fill the unused blocks with something. GALAX_7F.128 is the position 7F 27128 EPROM file for the original version of Galaxian. SGALX_7F.128 is the position 7F 27128 EPROM file for the Super Galaxian version. You can use either of these files.
Galaxian 2 Game Mod using one 27256 EPROM. Necessary equipment:
Note: If you have done the single 27128 EPROM modification (outlined above), this is the same procedure with some additions. PCB Modification steps.
You can now switch between the two different version of Galaxian with the attached switch. Galaxian ROM code explained.
$0000 - 07FF Galaxian 7U $0800 - 0FFF Galaxian 7V $1000 - 17FF Galaxian 7W $1800 - 1FFF Galaxian 7Y $2000 - 27FF Galaxian 7Z $2800 - 2FFF Galaxian 7W (filler) $3000 - 37FF Galaxian 7Y (filler) $3800 - 3FFF Galaxian 7Z (filler) $4000 - 47FF Super Galaxian 7U $4800 - 4FFF Super Galaxian 7V $5000 - 57FF Super Galaxian 7W $5800 - 5FFF Super Galaxian 7Y $6000 - 67FF Super Galaxian 7Z $6800 - 6FFF Super Galaxian 7W (filler) $7000 - 77FF Super Galaxian 7Y (filler) $7800 - 7FFF Super Galaxian 7Z (filler) This is 32768 bytes, or 32K. You need a 27256 EPROM for this. You'll notice that I've duplicated certain ROMs in some blocks of memory, like in $2800 - 3FFF. I don't know if this is necessary. I had to fill the unused blocks with something. GALAX_7F.256 contains this code for the 27256 ROM images and contains both the original Galaxians and Super Galaxians.
Galaxian PCB Pinout and using Galaxian in a Pacman Cabinet. Power supply: Galaxian gets its input voltages from a 7 volt/12 volt AC transformer. Once this power is on the pcb, it is converted to 5 volts DC and 12 volts DC (essentially the power supply is built-in to the logic board). BUT you can hook up a standard switching power supply, which supplies 5 volts DC at 7amps (or greater), and 12 volts DC to the Galaxian 7 volt AC and 12 volt AC input lines. This causes no problems. My only suggestion is that you turn the 5 volt adjuster all the way up on the switching power supply. This will make the output voltage from the switcher close to 6 volts. The Galaxian logic board will draw this voltage down to 5 volts. Galaxian vs. Pacman I modified my Galaxian PCB so the speaker is (component side) pins F and H (like on Pacman) instead of pins V and 18. This way I can just flip my Galaxian board into my Pacman cabinet when I want to play. Note: If you hacked your Pacman wiring and used a Regulated power supply to supply pin 18 with +5 volts DC, do not install your Galaxian board! If you are using a regulated power supply, wire it conventionally to the +7 volt DC pins. It will work fine in this manner! wire | wire Pin Componet side color | Pin Solder Side color --- ------------- ----- | --- ----------- ----- A GND (center tap 7v) | 1 GND (center tap 7v) B GND (center tap 7v) | 2 GND (center tap 7v) C +7 volt AC | 3 +7 volt AC D +7 volt AC | 4 +7 volt AC E Key (7.5 vdc out) | 5 Coin Meter in F (Pacman speaker) | 6 reset H (Pacman speaker) | 7 Coin Meter out J Coin mech switch | 8 K Test switch | 9 Credit switch L Select one player | 10 Select two player M P1 move left | 11 P1 move right N P1 Fire | 12 P2 Fire P P2 move left | 13 P2 move right R to GND for cocktail | 14 S GND for RGB | 15 GND for controls T RGB Red | 16 RGB Green U RGB Blue | 17 RGB Neg Sync V Galaxian Speaker | 18 Galaxian Speaker W +12 Volt AC | 19 +12 volt AC X +12 Volt AC | 20 +12 volt AC Y GND (center tap 12v) | 21 GND (center tap 12v) Z GND (center tap 12v) | 22 GND (center tap 12v) |