Skip down to 4/28 postings for more current - the problem turned out to be 2 things - 1 a missing spring on the fault (solved) and 2) the top ball popper which fires every time another solenoid (pop bumpers, controlled solenoids - but not slings or flippers) fires.

OLD post below:

The VUK is not getting the ball up on the first try on this Earthshaker which is being run by a sys 11 (no letter) board. When the game mode is not ready to do the earthquake (fault line, flashers, shaker motor), the VUK works great. When the quake mode is on kit *always* takes a couple tries as in the video below. NOTE that the plunger is fully extended before the ball gets there, but its not under full power as it falls down with a slight touch.

Things I've done or noted:
1) Coil & plunger have been swapped from the other VUK, problem did not move
2) driver and pre-driver have been replaced, thought they might have been flakey.
3) switch & switch diode good
4) no mechanical interference - and I believe the repeatability of the error makes this an unlikely cause
5) 75v at coil, but coil drops to 70v if a flasher relay in energized (this was during attract mode, I have not attempted to measure during game play.
6) The pulse on U17 seems correct - momentary based on the switch. One thing that I did notice, and it may be my mind playing tricks on me, is that the "second" signal pulse seems longer.

I feel like I've ruled out everything from the U17 through to the plunger... not sure where to go next -Thoughts?

Thanks - the switch is communicating perfectly with the CPU - the signal pulses upon switch activation every time. Do you still think it could be the issue?

The more I think about this the more I think it either is something on the board that effects the pulse duration or its the voltage getting robbed while everything is happening. To test that though, I'm gonna need to learn how to use the max/min function of my meter I think because its gonna be hard to see.

Bump. The repeatability of this error makes me thing the culprit isn't something flakey - its not intermittent - it happens everytime the earthquake is triggered.

Any ideas on how to verify/test either of these thoughts from above?

5) 75v at coil, but coil drops to 70v if a flasher relay in energized (this was during attract mode, I have not attempted to measure during game play) Maybe the voltage drops way lower when the quake is happening?

6) The pulse on U17 seems correct - momentary based on the switch. One thing that I did notice, and it may be my mind playing tricks on me, is that the "second" signal pulse seems longer.

Thanks - I'll look into that. I bought this as a project so I didn't know that wasn't normal. I'll ask the earthshaker club if this is normal!
thx

I thought this too - that's why I've checked for all mechanical interference (none) and even swapped the plunger/coil mech with the other VUK - also, see the next answer:

ONLY when its trying to lock the ball - I was calling this the earthquake. It works 100% reliably otherwise. This seems to confirm that its not really mechanical in the VUK assembly - to me anyway.

This is useful - I'll start here by removing that mechanism from the equation and then seeing if the VUK is successful, if so I'll rebuild the fault assembly and see if that helps.

Thanks again!

The switch for the VUK was adjusted and cleaned - and works reliably when the fault isn't happening. I haven't done a thing with the fault yet - I'll be able to mess with it next week and report back.

So - the fault spring was disconnected - the fault now seems to work ok. I still have issues with the Vuk though as it fires often - in fact, it fires any time ANY of the 3 pop bumpers fires (EDIT - or in fact ANY other controlled solenoid). This happens even in switch test modes. I do notice, however, that when using the switch levels test any pop switch can be held down and the vuk fires, but the vuk switch doesn't register. It does in the edges test, but I think that's because the plunger is triggering it, not a switch matrix problem

I don't get how the pop bumper is triggering the vuk... With my logic probe, I necked U17 - it is NOT sending a signal for the vuk to fire when the pop is switched, so this doesn't seem to be CPU problem - for the record, its not the transistor firing either.

This seems to lead to a short with the wires controlling the other coils and the vuk leading me down the route of looking for wire damage. Any other ideas?

Nope. I tried again this morning to be sure - I can take the switch off the playfield and insulate the contacts and it still happens with every coil fire.

I've been thinking about this for a while, and fear the problem may be somewhere else? How would the Vuk solenoid fire when every other solenoid (except flippers, slings) fires? I'm almost thinking that I need to dig in to the schematics and see if something is not wired properly. I bought this machine not working and its safe to say that there have been some modifications made, such as using the sys 11 CPU board.

Chime in if you have ideas, I'm also going to name the thread to more accurately describe the current problem.

Thx viper - headed out to the shop now. The short idea is interesting, but I'm surprised it wouldn't lead to the error in reverse; e.g. vuk fires then something else fires. As for the U17, it does not change output signal when the vuk fires because something else did - only when its supposed to fire. This is why I feel like its safe to eliminate everything downstream of the transistor. No test Rom here.

A

I also removed 1J12 from the CPU which is what fires the Vuk - but it still fires.

New theory - the Road Kings jumper requirements (this is a road kings board) are different than earthshakers - so I'm going to try to figure out those differences..

Real time blogging -
I removed anything brown/green from the CPU and aux power - still the problem; however, then I removed the J12 from the back box interconnect - and bingo -- so now I know where to concentrate.

Thanks - I'll look into the jumpers later. For now - its the one connector J11 on the interconnect board that has 1 wire - I can pull that one and the game works. I seem to recall that being for a GI relay or something - time to check

Found it!! Someone before me ripped the pin out of the 3rd spot on this connector, then just pressed the wire into the 2nd spot. The previous owner probably didn't realize this had been done and installed the connector like normal (not shifted 1 spot). I know this was a problem the previous owner had, so I'm not blaming him - the guy before him!

I guess the flash relay was enough to get the vuk to operate....

Anyway, thanks for the suggestions, it really helps to be able to type these problems up and get the thoughts clear about what's happening.

WIN_20140428_114620.JPG