I'm shopping a Road Kings and I'm having an issue with the right gate coil and the lower jet.

Bottom bumper - This one is weird, when I ground the transistor it fires good and strong every time. In test or gameplay it won't respond for the first several hits. If I leave the coil test on you can feel it hum and if you watch it below the playfield it has slight movement. This is for the first 10-20 hits then it will start firing strong and seems to stay that way until it has been off for a while. So far I completely disassembled it, cleaned all components, new coil sleeve, adjusted switches, new coil diode, new driver transistor and new pre-driver transistor.

Right Gate - This is one of those tiny coils that just has a little spring attached and pulls up the roll under gate. This is just plain dead, fires fine if grounded at the coil or driver transistor, nothing at all during test. So far I've replaced the coil diode, driver transistor and pre-driver transistor.

Okay, I'll check this when I get home tonight. Assuming I'm not getting a a signal at the predriver (since everything downstream has been replaced), where do I go from there?

After another 5 hours chasing this around with two electrical engineers and replacing the driver & pre-driver transistors of all of them I gave up and took it to a local repairman with a system 11 test fixture. He updated the ROM, changed out the processor, checked sockets and reseated chips. Only Q77 was fixed, and he said he is not able to get Q31 or Q9 operating again. I'm not sure where to go from here besides just replacing the entire thing.

Okay I got it fixed, there was actually two problems compounding so it threw me for a loop. U19 and U20 were both replaced which got Q31 firing again but Q9 was still down until the processor was changed out. Everything is working now except that lower jet is still very slow. Since it's def sending a signal during test I'm going to try swapping out the coil itself.

If I remember right it was the 6820 at U10.