Before starting, I recommend testing each voltage and making notes as to what values are found. It is helpful to know if the circuit was working properly before work was started. The original Williams schematic has invaluable suggestions as to test points and what components are likely to be faulty given different measurements.
I routinely replace everything listed below with the exception of X3. In particular, the zener diodes and the large electrolytic capacitors tend to fail over time.
| Designation | Description | Qty | Mouser Part # | Description | Note |
| +5 VDC logic and +12 VDC unregulated | |||||
| C15 | 12000uF 16V axial cap | 1 | 647-TVX1C103MDA | 10000uF 16V axial cap | A |
| 1 | 647-TVX1C222MCA | 2200uF 16V axial cap | A | ||
| D7/D8 | MR500 3A 50V diode | 2 | 583-6A2-B | 6A2 6A 200V diode | B |
| X3 | 3A 5V regulator | 1 | 511-LM323K | LM323K 3A 5V TO-3 reg | |
| +100 VDC and -100 VDC displays | |||||
| C7/C11 | 100uF 150V axial cap | 2 | 647-TVX2C101MCA | 100uF 160V axial cap | |
| D3/D4 | 1N4004 1A 400V diode | 2 | 583-1N4007 | 1N4007 1A 1000V diode | C |
| R1/R4 | 39k ohm 1/2 W resistor | 2 | 261-39K | 39k ohm 1W resistor | D |
| R2/R5 | 680 ohm 1/2 W resistor | 2 | 293-1.2K | 1.2k ohm 1/2 W resistor | E |
| Z1/Z3 | 1N5990 3.9V 1/2 W diode | 2 | 78-1N4730A | 1N4730A 3.9V 1W diode | F |
| Z2/Z4 | 1N4764 1W 100V diode | 2 | 625-1N4763A | 1N4763 1W 91V diode | G |
| +28 VDC solenoids | |||||
| C13 | 100uF 100V axial cap | 1 | 647-TVX2A101MCA | 100uF 100V axial cap | |
Notes:
A Use two axial capacitors in parallel to approximate the defunkt original value.
B This is an upgrade to a higher amperage part. 6A4 400V, 6A1 100V or 6A05 50V all OK.
C This is a higher voltage upgrade part which I also use for playfield coils.
D This is an upgrade to a flameproof resistor with higher wattage.
E This is an modification recommended by Williams for higher reliability.
F This is an upgrade to a higher wattage part.
G This upgrade lengthens display life by lowering voltages from 100V to 91V.
After all board voltages test good, I recommend replacing 3J6 which is the large connector at top near heatsink. If this connection fails, it is possible to damage a CPU or driver board. Purchase Mouser Part # 538-26-48-1155 Molex .156 K.K. header 15 position.
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Page last updated December 15 2003.