Written by Paul Swan

This is what I did to convert my "Galaxians" before building a wiring harness 
to convert it to JAMMA. One of my boards had three of the four 7V AC supply 
edge connector fingers burnt away and so I "commandeered" the coin 
counter/lockout +7V DC supply pins to improve the power distribution. All the 
wire links added were 1mm solid core domestic wiring cable, rated 15A, unless 
stated otherwise.

Remove IR2 (78GU I.C.) 
Remove IR1 (D44VM4 transistor)
Remove R88 (50Ohm 5W resistor)
Replace D4 (A15F diode) with a wire link
Replace D5 (A15F diode) with a wire link
Replace D6 (A14F diode) with a wire link
Replace D7 (A14F diode) with a wire link
Replace R87 (4Ohm 10W resistor) with a wire link
(optional) Add a wire link from edge connector pair 18,R to edge connector pair 19,S
(0.6mm solid core, via to via - to use coin counter supply as 5v line)

A fuse, F1, was listed in the schematic but didn't seem to be implemented 
(explicitly) on any of my boards. If it does exist, it should be bypassed 
with a wire link and the whole supply fused at source.

For reference, here are the pinouts for both the original AC supply and the DC 
converted supply:-

AC SUPPLY 

Ground A 1 Ground
Ground B 2 Ground
12v AC - C 3 12v AC -
12v AC + D 4 12v AC +
Speaker - E 5 Speaker +
Video Blue F 6 Video Sync
Video Red G 7 Video Green
Ground H 8 Video Ground
Table I 9 NC
Player 2 Left J 10 Player 2 Right
Player 1 Fire K 11 Player 2 Fire
Player 1 Left L 12 Player 1 Right
Start 1 M 13 Start 2
Test N 14 Service
Coin 1 O 15 Coin 2
Coin Lockout P 16 Coin Counter
1 Play Lamp Q 17 2 Play Lamp
7v DC out R 18 7v DC out
7v AC - S 19 7v AC -
7v AC + T 20 7v AC +
Ground U 21 Ground
Ground V 22 Ground

 

DC SUPPLY 

Ground A 1 Ground
Ground B 2 Ground
+12v  C 3 +12v 
+12v  D 4 +12v 
Speaker - E 5 Speaker +
Video Blue F 6 Video Sync
Video Red G 7 Video Green
Ground H 8 Video Ground
Table I 9 NC
Player 2 Left J 10 Player 2 Right
Player 1 Fire K 11 Player 2 Fire
Player 1 Left L 12 Player 1 Right
Start 1 M 13 Start 2
Test N 14 Service
Coin 1 O 15 Coin 2
Coin Lockout P 16 Coin Counter
1 Play Lamp Q 17 2 Play Lamp
+5v R 18 +5v
+5v S 19 +5v
+5v T 20 +5v
Ground U 21 Ground
Ground V 22 Ground