Rebuilding the A8 high-voltage section

Steps

• Zeners: 1N4759A (62 V) at VR1; 1N4758A (56 V) at VR2 and VR3; 1N4742A (12 V) at VR4 and VR5.
• Diode: 1N4004 at D9.
• Transistors: 2N5551 at Q1 and Q2; 2N5401 at Q3 and Q4; MJE15030 at Q5 and Q6; MJE15031 at Q7.
• Resistors: 47K 1/2 W at R12-R15; 120 ohm 1/2 W at R16 and R17; 4.7K 5 W at R18; 1.8K 5 W at R19.
• Check the five display voltages before plugging the display back in, with power off for any connecting.

The A8 controller makes roughly +62 V, -100 V and -112 V for the display; keep hands off it with power on.

Systems

• Gottlieb System 3

Related tips

• Display voltages the A8 board should supply
• The A8 dot matrix controller board
• Never hot-plug the A8 board or the display
• DMD controller LED stays on
• Garbage on the dot matrix at power-on
• A5, A6, A8 and A20 plug identification
• Nonsense message at boot, game stuck in a loop

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)