So I picked up TAF, works well enough, save for that the kickout for the Thing hand/(skillshot) keeps going off randomly triggering the hand to try and grab a ball that isn't there and the coil that kicks the ball out keeps firing randomly. check the switch test menu, they all work fine, nothing stuck open. Look underneath and I see a resistor hacked between the connections for the micro switch for the kickout coil by the thing hand. Used alligator clips to take the resistor out of the loop and test and the game plays flawlessly... until you trigger the Thing hand ball grab, at which point the game Tilts. anyone run across this before? any ideas? I'll put some pics up later.

err yeah diode.... interestingly, reversing the connectors to the micro switch (putting the diode on the other side), results in it working fine for the first few minutes then once its warmed up, it resumes thinking the switch is being activated and keeps trying to kick out a ball that isn't there.

So did some more checking. When the Thing Eject Hole Switch is hit and the diode is not present on the microswitch, it triggers that switch and the bumper lane opto (for thing flips shot). If I add the diode in between the switch going one direction it only triggers the bumper lane opto, the other direction it only triggers the thing eject sol. Still randomly fires during game play after it warms up. Tried a different microswitch too (using gator clips) and it does the same thing. Also randomly got a a checksum error on U15 of the sound board but it went away after a couple times of being restarted, don't think that's related.

Seems like what is disrupting game play is when it locks a ball in the swamp scoop the plunger for the kickout hole keeps going off instead of the one to push the ball to the other side of the swamp scoops so that it can kick it back out onto the playfield.

So far all the wiring has matched the diagram, only hack I've found was that diode added to the white thing eject switch.

Just went through the switch test and confirmed they are all showing up as the right switch. Went through the diagrams and verified the wiring too.

here is the switch that keeps firing randomly.

photo.JPG.jpeg

So... question, the diode on the cpu board is 1n4841, is the one on the switch suppose to be the same? the one on there is 1n4004 currently. My plan currently is to start from the switch and work back replacing things now that I've confirmed it's not a wiring issue.

Screen_Shot_2013-08-04_at_11.11.59_AM..png

1n4004 is what's used on the driver board I believe..

Cool, then it's the right diode. I'll replace the diode and switch when the parts get in. Anything else you can think of?

Some more info... So when the issue happens, if I jump straight to the switch test menu. Switch 87 is stuck on. pressing the switch doesn't change the state of it. If I leave the machine on and put it into service position, I can see right as it goes completely vertical the switch goes back to working correctly. After that pressing the switch makes it register correctly in the test menu until I fire up another game and get GREED lit up or land on the Thing grab too many times then the switch locks on again until it's in position. Makes troubleshooting it kinda difficult. How would you proceed?

when switch 16 (center ball trough) is pressed, 86 (GRAVE A) also fires with it. Switch 17 (right trough) also triggers Switch 87!! (thing hole eject). when you first turn the machine on, most of the time, SW16 and 17 work fine and don't trigger the additional switch. Once its warmed up a bit or you complete the GREED to activate the lock, they begin triggering the additional switches. At that point it thinks there is a ball in the holder for the thing glove so it keeps triggering sol to kick it out of the hole, or the hand if you just completed GREED.

I just replaced switch 87, the diode, and microswitch 17 + diode. same issue Thinking about rebuilding the driver board and under PF boards next, still haven't found a short anywhere. Any additional recommendations?

@ steve could you elaborate on NC NO positions. It's wired as shown in the pic in above except its now a new switch that only has two pins instead of 3 (other than that it looks the same), the diode is floating (just soldered straight to the wire) and connects the white violet wires to the L shaped tab connector. The Green gray wire is wired to the other tab (middle tab on the old switch pictured).

@LTG & LOTR_b
The switch matrix is below, I'm about to begin going through it again, any recommendation on a process? start with the 16 & 17 switches and trace the wires verifying the color and order on the matrix? things to look for?

Screen_Shot_2013-08-06_at_7.51.31_PM.png

Currently switch 16 triggers 86
switch 17 triggers 87

switch 87 thing eject hole (where the ball is held for the hand magnet to grab it). seems to fire randomly during gameplay, probably the result of switch 17s issue.
Issue typically occurs the first time lock is lit (GREED).

Found it... so, some additional details, This TAF is running Gold roms and the previous owner added the extra ball button and patched the cables in on the same switch as the tilt works fine, until the diode that was just wrapped around the terminals goes out and every switch above plumb bob tilt also has a path to the other column, was hard to see because two of the switches affected were the Thing Opto's, one of which is normally on (opposite, when hand is out). Thanks, for the help guys, in the end, learning up on switch matrix theory was the answer, pinballrehab.com had a good youtube vid and article.

To clarify, removing the diode on the extra ball button resolved the issue.