Hey experts!
I have a Gilligan's Island been playing whack a mole with. I replaced a broken pop bumper stack switch which I thought was my last issue, and now the Top Eject hole solenoid is locked on.
The top eject switch in switch edge test is open, until I manually close it with my finger. The switch does not seem to be stuck closed at all, but the solenoid is constantly on.
I've tested TIP102 Q44 in circuit with the game off - it checks out per Clay's guide. DMM on diode setting, black lead on metal tab, red lead on left measures 0.62v, red on right 0.42v, red on center 0.00001v.
Also checked it for short by DMM in continuity mode, touching black lead to ground strap, and red lead to metal tab of Q44 - no beeping.
The predriver transistor Q43 also checks out - DMM on diode setting, black lead on center pin, red on right reads 0.67v, red on left reads 0.66v. Clay's guide mentions 0.4-0.6, and 0.67 is a little high, but all the other pre-drivers on the board test with the same reading and those solenoids are working fine.
I've tested the LS374N as well. Pin 12 which drives the pre-driver transistor. Placed black lead on ground test pin, red lead on pin 12, measured high at 4.95vdc. My understanding is that High is the normal setting for passive solenoid, and that when it is low it should activate the solenoid.
It looks like the TTL chip, the pre-driver, and the TIP 102 are all good (I know they may test fine but fail under load).
What would your recommendations be at this point? Test the diode? Resistors around the transformers? Look for some other short?
My island motor and opto switch are not working properly yet, which is the only other issue I've seen so far with the pin.
