Demo man cryoclaw headache

[smartbomb2084]

Hello all,  I have a Demo man that upon game turn-on the claw cycles as it is supposed to do.  Except it only turns right and will not come back left to the 'home' position above the ACMAG ramp.  The claw has been disassembled and the wiring to the switches have been checked thoroughly.  The solenoid wiring that drives the motor has also been ruled out.  The claw seems to function properly when it is in test mode.  I have monitored the 74LS374 flip-flop that drives the solenoid and the  CPU does not activate the claw to the left at turn-on or in game mode.  It is as if the CPU thinks the left position OPTO is already closed but the tests show otherwise.  I am about ready to just change the u-shaped optos as a shotgun approach because I am out of ideas.  Interesting, isn't it?

[ChadTower]

Swapping out the optos isn't a bad idea... have you checked for breaks in the wire between them and the CPU? 

[smartbomb2084]

The switch wires to the CPU are fine.  All the other switches in the associated row and column work fine too. 

[Karetaker]

Check your manual. I'm going from memory here so don't quote me. Look at where the plug comes into the board for your claw. I believe it is the lower left side of the driver board. Again, don't quote me consult the manual. More than likely you will have to replace the pins in that plug. I would use trifurcon(sp?) pins for better contact. But, that seems to be a common problem with this pinball machine.

[smartbomb2084]

You are probably referring to J118 as the connector in the lower left corner of the power driver board as this is the +12V supply that runs all the switch optos.  It has been thoroughly checked out and determined not to be intermittent.  The problem seems to be that the CPU does not bring the 74LS374 flip-flop output 'low' in game mode to drive the solenoid that runs the claw motor left.  The CPU does drop the output 'low' in test mode however.  This has been confirmed by monitoring the flip-flop's output with a logic probe.

[Karetaker]

Maybe I'm wrong. But, I saw this exact problem and it was whored out pins on that plug. If it were me I would change the header pins on the board and pins in the plug. But, that's just what I would do. Good luck with it.