"CHECK FUSES F115 AND F116, J112 AND OPTO 12V SUPPLY" (WPC-89.)
This error message appears when all the opto-sensors are affected at startup. This happens in the absence of 12 V.
1. Check fuses F114, F115 and F116.
2. Remove and reinstall connectors with +12 VDC: J114, J116, J118 and J119.
3. Remove and reinstall all the ribbon cables in the backbox.
4. Make sure the ground braid coming up from the cabinet is securely connected to the steel plate that holds the circuit boards in the backbox.
5. Check the connectors on the opto boards, both on the transmitter and detector side, in the ball trough.
6. Make sure the LED on the opto board under the playfield is lit. Remove and reinstall connector with supply voltage (J3).
Check that there is +12 VDC on J3-1 on this opto board.
If the voltage is ok, the problem may be one of the two circuits U1 or U2 (LM339). Try swapping opto board with another game, or swap these two circuits.
If the voltage is not ok, check J118-2, if it is +12 VDC from the power driver board. If the voltage is the same as on J3-1, then move on to the next point, otherwise switch the connectors.
7. Check that it is +12 VDC at test point TP3 (regulated 12 V). If it isn’t, check the voltage +18 VDC at test point TP8, as this +18 VDC is converted to +12 VDC with a voltage regulator LM7812 (Q2). If the 18 Volt is not correct, it is probably bridge rectifier BR1 / capacitors C6 and C7 that need to be replaced. If 18 Volts is ok, but 12 Volts is not ok, diodes D1 and D2 or voltage regulator Q2 are to be suspected. Check D1 and D2 (DMM in diode position. 0.4-0.6 VDC in one direction, and no value in the other direction.). If these measures ok, then change Q2.
8. Check that there is +12 VDC at test point TP1 (unregulated 12 V, normally measured to about 15 VDC.). If the unregulated voltage is below about 11 V, the opto sensors will not work properly. You probably need to replace the BR5 / C30.
9. Check that the AC voltage coming in from the transformer is ok. It shall be 9.8 VAC between J112-1 and J112-3.
10. Disconnect an AA battery to reset any memory errors.
11. If the points above are ok, it may be U20 that has broken and needs to be replaced.