F14 - System 11 Board Troubleshooting Help

(Topic ID: 220817)

F14 - System 11 Board Troubleshooting Help

By statictrance

4 months ago

Topic Stats

  • 2 posts
  • 2 Pinsiders participating
  • Latest reply 4 months ago by wayout440
  • No one calls this topic a favorite


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#1 4 months ago

Trying to troubleshoot my F14... Long story short - I was moving and had a lapse between houses and let my neighbor with kids borrow it... Now I have it back and after initial troubleshooting, the 'kid did a bunch of short plunges that caused the diverter coil to lock on and cause havoc' story we've all heard about is almost assuredly what happened to the poor machine. What's tripping me up following repair guides and review on here are some of the values I'm seeing and all the various components I need to check. The symptoms aren't matching what I'm expecting to see...

First of all - the only physical damage you can see on the board is the lower diverter TIP was smoked. It tested badly, I replaced it, and threw it back into the machine to test it through after replacing the fuse.

The lower diverter coil I completely removed from the machine and tied the power cable together to test through the rest... When I turned the machine on - The upper diverter coil now locks on. Also (through a very fast test mode) - the following oddities were found

1 - VUK kicker, Kickback, Jagov Kicker all fire as needed when the test coil hits them, but they then stay engaged instead of reverting back to their regular state. You can hear it continue to pulse them if you leave it on - but the plungers all remain engaged.
2 - Flippers are active as soon as the machine comes online
3 - The upper diverter locks on as noted above

I checked the TIPs for the above coils - but they all return fine. So my question is - what all items should I be testing here? SHould I focus on the predriver? Resistors? Diodes? (coil and/or diode board?). The Zener Diode? Or do I need to even go through a logic check on 7402?

Nothing else looks to be damaged, so I was hoping to have an idea of where to be searching. Thank you all in advance!

#2 4 months ago

Use a logic probe or oscilloscope to check upper level logic signals feeding to the predriver for the coils that are locking on. The type of symptom you describe where the coils activate in test mode, but do not revert indicate this isn't a passive type of problem: for example, if the predriver transistor was shorted, or some other "hard" failure,the coil would be locked on continuously as soon as the game was active. The fact that the coils are actually off in test mode until called upon by the logic to fire indicates some type of upper level logic issue (PIA perhaps)

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