Tech: F-14 reset problem, coils fire at game start-up

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Bob Stemmler

25 okt. 2002 16:57:442002-10-25
I've been working on an issue I am having with my F-14 tomcat,
Williams system 11A. Everytime I press the credit button to start a
game, all/most??? of the multiplexed coils fire immediately, which I
think is making the game re-set to game over status, because of a
sudden voltage drain. The symtoms are:
-Press credit button to start game, most/all of the multiplexed coils
fire immediaely, game does not start, or resets? The coils that fire
for sure are contolled by solenoids 01A, 03A, 05A, 07A,
- Game diagnostics work. In solenoid tests, the Solenoid A/C Select
Relay seems to work , multiplexing between the A side and the C side.
When I groung the tab on transistor Q7 I can hear the A/C Select click
- when in solenoid tests, the right eject fires for the solenoid 7A
test as it should, the right eject coil ALSO fires for the "flasher
7C" test. I know this should not be.
- Before I got to this point where game would not start/or reset, I
started getting some weird behavior. What would happen is that the
right eject would fire several time in quick succession when the
flashers should have been activated(like at free game award or extra
ball award). Then last week, the right eject would occasionally fire
when a flipper was activated. As I stated, it has now degenerated to
firing upon game start-up.
-I have also tested tansistor Q30 which drives solenoid 7 that
controls the right eject and #7 flasher. Does not seem to be shorted,
and when grounded it will fire the right eject coil. I also did a
quick test for all of the other driver transistors by checking for
shorts to ground from the tab to the ground strap.
- I am suspecting that it may have something to do with the Select
Relay that multiplexes between the "A" bank and the "C" bank? The only
problem with this theory is that I get separate coil and flasher
activity on the other multiplexed circuits. Should I just focus on
solenoid #7? But then why do other coil fire at game start? Or is this
more likely something further upstream. Or maybe something further
downstream like a bad diode on one of the other cois that are daisy
chained into the select relay? As you can see, I could use some help
in trying to narrow down where to focus. Any help is greatly
Thank you!
Bob Stemmler

J@ker P@ker

Enver Haase

25 okt. 2002 17:13:382002-10-25

I must admit, I haven't re-thought that one twice.

However, if you believe it's an A/C select relay problem,
but you think the relay is okay and you even think the
TIP 102 that drives the relay is okay, why don't you suspect
the pre-driver transistor to be defective or the IC or SRC or
whatever comes next upstream of that one?


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