Tom's Eight Ball Pinball Machine Restoration

Condition as received

  • Left and Right Bank Shot arrows not lit
  • Missing score/settings retention battery
  • When left on for a period of time the MPU begins functioning erratically. In one case it turned on the 10 point chime steady and burned it out along with its driver transistor.
  • Digit 5 of the 1st player display stopped working
  • The switched lights were dim, especially during test mode where all lights blink.
  • The chimes didn't have a very good tone.
  • Game occasionally starts with Tilt on.
  • Missing one coin mechanism.

Restoration activities

  • Placed Instruction Manual, Schematic and Insert cards on web site
  • Replaced bulbs and cleaned sockets
  • Mounted a 3.6V Ni-Cad battery from a cordless phone in the cabinet and wired it to the MPU board
  • Several lights, switches and selenoids stopped working. Trouble-shooting revealed a low signal on one of the output lines from U10. This was traced to a bad insulator on the credit button.
  • Replaced the 10 point chime transistor (Q1) on the selonoid driver board with a good unused one on the board (Q2).
  • Replaced the 10/100/1000 chime unit with a better sounding one instead of replacing just the burned out 10 point chime coil on the old one.
  • Swapped 1st player display with credit/ball/match display to place bad digit 5 where it wouldn't interfer with play. Found that digit 6 was out on the one moved from the credit/ball/match position. Found a burned out 100k resistor and replaced it with two 1/4 watt 47k resistors in series to achieve a 1/2 watt rating.
  • Found bad 2N5401 transistor for digit 5 on the display now in the credit/ball/match position. Moved the 2N5401 from digit 6 since it isn't used on this display position and ordered some 2N5401 transistors.
  • Measured switched light supply and found that it was only 3 volts and showed only half wave rectification on the oscilloscope. Replaced BR1 and problem was solved.
  • Removed capacitor across tilt switches and tilt problem went away.
  • Installed missing coin mechanism.
  • Occasionally the MPU will not start right after power on. Reseating the integrated circuits corrects the problem. When I left the machine on too long after an improper startup with the outhole kicker engaged, it burned out the solenoid. I ordered a new one but placed it on the side return kicker since it had not been kicking the ball quickly enough hoping that it would improve the kicker's performance. The burned up out hole kicker solenoid was replaced with the old solenoid from the side return kicker and the burned out fuse on the 43V line under the playfield was replaced.