Tech hlep needed: Stern Viper locked on coil

splinch

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Trying to get a Stern Viper going,game will boot up in attract mode.The right slingshot kicker coil locks on as soon as I start a game. I replaced the tip102, 1n4004 diode, associated CA3801 IC and 74154 IC on the solenoid driver board. I replaced the kicker coil, checked the sling shot switches and cut the switch capacitor. I'm at a loss, anyone else have any ideas?

A second annoying but less serious problem is sometimes the turrent after the ball fires from it, won't return to home position (12 oclock).

thanks

James
 
Trying to get a Stern Viper going,game will boot up in attract mode.The right slingshot kicker coil locks on as soon as I start a game. I replaced the tip102, 1n4004 diode, associated CA3801 IC and 74154 IC on the solenoid driver board. I replaced the kicker coil, checked the sling shot switches and cut the switch capacitor. I'm at a loss, anyone else have any ideas?

A second annoying but less serious problem is sometimes the turrent after the ball fires from it, won't return to home position (12 oclock).

thanks

James

I'd start with the basics, like ohming out the path from the coil to the driver board, making sure it was the right TIP102 you replaced, etc. (schematics have been wrong before.)

A quick check - if you disconnect the connector at the driver board that carries the wire for that sling, does the coil still stay locked on? If so, there's a short to ground on that wire somewhere on the playfield. If not, the problem is on the driver board or in the switch side of things. With the power off and connector disconnected, do you measure a short to ground from that sling's connector pin on the driver board? If so, there's a solder splash or a cooked TIP102. If not, then problem is in the drive circuitry (either locked on, or the switch input somehow shorted) And so on. Just divide the problem at various convenient physical and logical breaks and figure out which side the problem is on.

Duncan
 
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