Starting to dig into my Taxi tonight...The Marylin drop targets don't reset at game start up, or during game play, but they do reset during coil test...Any suggestions????
You guys....stop pulling his leg.
Optos are switches based on photoelectrics. Instead of a physical switch like a leaf switch or microswitch closing, and opto uses a transmitter to send a narrow beam of light using an LED to a receiver that detects this light. As long as the receiver sees the light all is good. When the light is blocked, the receiver detects that a 'switch' has been made. Most of the WPC era of games (90 and on) use them. There are special OPTO boards that supply power to these light emitters/receivers and interpret the signals to send them back to the MPU as part of the standard switch matrix.
As for your original problem, check the switches that detect that your taxi drop targets are down. If one of them isn't making then the coil doesn't know to reset the targets.
Switch levels show just that....the level, or current value (on or off) of the switch.
Switch edge shows the transistion from off to on only, and usually is a more useful test, as it only shows one switch at a time. That way if you trigger one thing like a target, and more than one switch registers in switch edge test, then you have a problem.
Go into switch edge test and trigger some other switches....specifically ones in the same column and row as those targets (look at your manual at the switch matrix chart). See if anything else registers as those targets.
Oh, and in switch level test, when you triggered the targets did they stay on, or come on and then off, while the target was still down. In the case of targets, switch level may be a more useful test, as perhaps the opto sees then unsees the target while it is down.
In any case, if the solenoid works in diagnostics but never fires in the game, then the game thinks those targets are up.
I'd check the two connectors on the opto board, reseat them, make sure no cracked solder joints as these opto boards get beat due to vibration.
I'd then clean the optos with some windex and a q-tip.
If that doesn't fix it, swap the opto boards and see if the problem moves to the other bank of targets.