Hi guys- newer member to bop club. Could use some assistance. I bought this game not booting with playfield in a box head motor not working at all. Wont move in test mode.

I got the game to boot- blanking circuit issue. Reseat chip on mpu and all is well.

Now I'm working on the head portion. To be honest- I'm not following theory of operation.

head apart- switches work. Coils for ball eject work. Bench test motor it works. Yet head does not spin

Q22 for head relay works. My understanding is the relay is to control rotation' ie clockwise or counter clock wise? Is this correct?

Q20 for head motor I'm not certain what I should see. I do know that when testing transistor with multimeter it reads similar to q22. So nothing jumps at me saying bad.

At driver board j122 has 4 wires populated in plug. J122-1, 2 and 3 are at 12V. J122-4 I have nothing. Pin 4 corresponds to q20 that is head motor transistor. Should I be seeing 12v there? If so then thats an issue.

But where hell is the 20v coming from to the motor regulating board? Because I do not have 20v on j1/1. Nor do I have 12v at j2/1

Right now- my gut is saying j122/4 should have 12v. But until I understand theory of operation I dont want to rip anything apart.

Worse case this upcoming weekend I can get access to a working machine and get values off it to compare with mine see what's missing.

Yet hoping someone can fill in the blanks for me. Attached pics of diagram if that helps

Thanks

Mike

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Just a follow up to above post now that I understand theory of operation. Found where 20v comes from and all makes sense now that I have all 3 diagrams to complete circuit. Just above 2 dont tell whole story.

Basically need the 20v- that would be the start of the circuit. So from transformer through bridge to board and out. Led 5 iirc is the check bulb for the 20v circuit.

From board the 20v goes into motor reg board and is regulated to 12v. That 12v is sent to relay assembly and q20 transistor. The q20 when operated is the ground to complete circuit that allows head to spin..

Q22 for relay is there to swap direction of motor.

Im bot use to working on wpc William's but i find it odd they didnt have a 12v power supply that they took 20v and regulated it down.