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?
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?