Important Note: Credit Board installation to original LAI Skill Tester

The relay coils and gripper coil of the 1980’s LAI Skill Tester generate back-EMF spikes of 150 volts and more which need to be suppressed when interfacing a Sunrise Credit Board to the system. The credit board may have a problem with resetting, thereby losing credits, or the LED credit display may be corrupted. Without this modification, credit boards using the new low power CMOS “SR3” processor chip are particularly susceptible to this problem.

(These precautions are not needed if the machine has been fitted with a Sunrise Skilltester Upgrade Board. click here for information about the upgrade board.)

Five 1N4004 diodes will be required, for the three large relays, for one of the two small relays and for the gripper coil. The principle here is the same as that used by electronic pinball machine manufacturers, where a diode is soldered across each coil.

Skill Tester EAV85 Relay Board. Solder four 1N4004 diodes to rear of Skilltester relay board, across the terminals of four of the relay coils. Observe the diode polarity, indicated by the band at one end.

Gripper Coil. A 1N4004 diode is fitted to the gripper coil terminal block. Fit the diode to the main wiring harness side of the block, so the diode will not need to be disturbed in the event of future curly-cord replacement. After checking that the polarity of coil connection in your machine is as shown, fit the diode, band end to the positive (+) side. Use plastic tubing to insulate the diode from possible contact with the metal cover.

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