I just led'd my BK2K and wanted to fit LEDs to the pop bumpers. If you've ever tried this you will know that most LEDs are just too tall. I have a few different types here and managed to fit some that weren't THAT much too tall, but the bumper cap still pressed down on the led as I tightened the screws. Turned the machine on and liked the result. Played a game and noticed the pop bumpers had stopped working. Had a quick look at them and they looked fine but the fuse had blown under the playfield. Replaced the fuse and fired it up. Pop bumpers still not working. Hmmm....wait...what's that smell? One of the bumper coils was melting and the bumper was stuck in it's activated position.
So what had happened? When I pressed down with the bumper cap the lamp holder had twisted slightly so one of its corners was able to press down on the top of the bumper skirt where it locates in the bottom of the bumper body. This pressed the skirt down vertically closing the gap in the normally open switch that activates the bumper. As it's a system 11b " special solenoid " that switch can directly activate the solenoid and lock it on if held closed.
I replaced the coil but it was still activating on power up. Board removed, transistor Q75 was bad, replaced. All working fine now.
So what had happened? When I pressed down with the bumper cap the lamp holder had twisted slightly so one of its corners was able to press down on the top of the bumper skirt where it locates in the bottom of the bumper body. This pressed the skirt down vertically closing the gap in the normally open switch that activates the bumper. As it's a system 11b " special solenoid " that switch can directly activate the solenoid and lock it on if held closed.
I replaced the coil but it was still activating on power up. Board removed, transistor Q75 was bad, replaced. All working fine now.
