gottlieb system 80 driver board 74ls175 transistor/coil locking on.

ixtlann

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gottlieb system 80 driver board 74ls175 transistor/coil locking on.

Using my hh to get this other machines boards right. Boots up fine, mpu/cpu good by swap. Driver board. Ok at first but once you start a game the lower playfield lamps turn on, and the lower pf up kicker relay turns on and both stay on. The problem has been narrowed to the driver board. I thought I replaced the correct associated transistor for upkicker relay. But no change. I assume I should suspect the sn74ls175 that runs that transistor. I followed that trace back to the correct one but did not notice anything out of ordinary on the legof that ic. But I am not sure I am testing it correctly. How should I be testing it?
 
I am having the same trouble with my Xenon... the ball release solenoid wants to kick on and stay on. I have been fighting this for a while.

You can eliminate the control chip by interrupting the circuit to it. On my board there is a diode that is between the control chip and the transistor circuit. If your de-soldier one end of the diode and pull it up... you have then interrupted the controlling circuit. Then flip on the machine and see if the solenoid still fires. If not, then 'jumper' the end of the diode you removed to the point where it connected and see if the solinoid comes on.

I'm thinking if I (you) isolate the transistor circuit from the controlling circuit, I (we) can then narrow down where the problem lies.

Just a suggestion.

BTW, I still haven't resolved mine yet. :-(
 
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