Quoted from KSUWildcatFan:
Ugh. Still fighting my right pop bumper. I'm pretty sure all that was wrong was a skirt/spoon alignment (just pressing the skirt up top, it was clear it didn't press the same way as the other two) but now, after messing around with the leafs I have zero action whatsoever on that pop. Then, looking at the board to see if something stood out, I saw this wonderful 'fix'. I don't think it's a contributing factor to this issue, but... Wow.
Back on task, just how are people adjusting pop bumpers on these? No matter how I prop the playfield, I can't seem to contort myself in such a manner that I can do much of anything pop-related with any ease. It's beyond frustrating.
You can *carefully* lift the playfield all way so its pointing straight up in the air, then gently slide the back of the playfield forward just a bit and lean it against the back box. Just make sure it has several degrees tilt towards the back box and its not perfectly straight up, otherwise it could accidentally fall down. All of the wire harnesses are more than long enough to allow you to prop the playfield up like this. You'll have to first lift the playfield then slide it way out forward. You may have to stand on the side of the machine and actually lift both the front and back of the playfield to kind of scoot it into position. Its not too hard though. Then you will have direct access to the underside of the pops with nothing in the way. TAKE THE BALLS OUT FIRST!
Which transistor is that in the pic (with the hot glue around it)?
You could try lifting the playfield as described above (with balls taken out), turn the machine on and put it in diagnostic mode. Then you will be able to test the leaf switches on the pop bumper directly, measure voltage, etc.
Also test the TIP transistor that is associated with this pop. There is a small chance maybe if you shorted one of the leafs and the coil was stuck on too long it may have fried the driver transistor.
I'm not sure if this is a recommended solution but you could use very fine grit sandpaper and electrical contact cleaner and very gently cleaned the leaf contacts without bending them.
When all else fails always check continuity everywhere, even between the tip of the leaf and base of the solder lug, all the way up to the header pins on the CPU board.