Galaga Power Supply Board  
for your Galaga video game
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    J2 is the DC  power out on the power supply. It supplies the +5 volts (PCB logic ), +12 volts (audio), and the +7.2 volts (coin meter). In this picture, J2 is red in color  >>>
   J1 is the low-voltage AC power in. Wiring harness P1 supplies the following voltages: 14.5 VAC , 9VAC, and 12 VAC. In this picture, J1 is white in color   >>>

 

     Inspect  the contacts with respect to  J1, P1 and J2, P2.  Note: Never remove these connectors with the power switch on. Doing so may cause damage to the main PCB or to the power supply board. Always have the power switch off when removing or installing parts inside a video game.  If you are unsure at this point, then remove the power cord from the wall outlet before proceeding.
     The contact surfaces of the pins in these connectors become contaminated over time.   Resistance will build up between the two metal mating points in the plug / jack. This results in a voltage drop at that connection, and may cause that position in the plug to overheat. This only compounds the problem. This is usually evident as a burned, or discolored appearance of the plug, at the failing position(s). If this is the case, it must be repaired. As well as being unsafe, incorrect voltages will cause unreliable operation.

   
With the two plugs disconnected from the power supply board, slide the board out. Take fine sandpaper, or use a small wire brush, and clean the pins on J1 and J2. Clean all around the diameter of each pin for maximum contact exposure. 

    
 
 Wipe any dust created, and re-install the power supply board back into cabinet. Insert plugs P1 back onto J1, and P2 back onto J2.
Voltage considerations
 
    The Galaga PCB set must be operated at 5 volts +-.25 volt - never more than 5.25 volts, never under 4.75 volts. Over voltage will cause damage, while under voltage will usually result in unreliable, or unpredictable, operation. 
    The +5 volts can be adjusted via VR1, as shown in the above diagram. Using a digital multimeter, measure the voltage at the game PCB. This can be done on the 3-wire connector near the 22-pin edge connector on the game PCB. Connect the negative(-) lead of the multimeter into the back end of the 3-wire plug, (center position), while it is inserted on the PCB. There are 2 other pins, one on each side. One of these pins is the +12 volts. The other is the +5 volts. The +5 volts is closest to the 22-pin edge connector. When you measure this voltage, it may be less than 5 volts. If it is less than 5 volts, adjust VR1 clockwise until 5.10 volts is obtained. If you cannot obtain at least 4.85 volts, there is a problem. If you cannot adjust the voltage to be less than 5.25 volts, there is a problem.
     The +5 volt reading may also be taken across the capacitor C1. On the game PCB, this capacitor is the 470 uf 16 volt electrolytic, located right next to the 3-wire power connector. Negative (-) is the lead facing the corner of the board. The positive (+) faces the 22-pin edge connector.

 

Last updated October 10th, 2007

 

 
Contact me at greg@gls1electronics.com if you have any questions about your Galaga game.