(Topic ID: 299839)

Need some help with system 11 coil/switch issue...

By cosmokramer

2 years ago



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#1 2 years ago

Im doing a few minor repairs on a friends pinbot. I have everything fixed except the left jet bumper. Neither the switch or the coil work in test mode or game play. The coil fires if I ground the tab on q73
System 11 troubleshooting is not my strongest skill so I could use a little hand holding here.(The repairs I was asked to do originally were mechanical issues, I just want to see if I can fix this problem for him as well)
I confirmed continuity from both the coil and all switch wires to the connectors at board and all is good.
The lower scoring switch on that stack works.
Please advise, thanks

#2 2 years ago

As you have already tested the playfield wiring path (grounded transistor tab) the problem is likely on the board. You mention the software is unable to turn on (and ground) the transistor and this provides more evidence it is on the board.

There are two paths to enable the transistor.

  1. The software side is driven from the PIA to the 7407 (U49) to the 7402 (U45).
  2. The hardware side is driven by the playfield trigger switch (SS1T) to the 7402 (U45).

You will likely need a logic probe to isolate where in the drive circuit the problem is. You can manually ground the playfield trigger switch by grounding pin 5 of 1J18. Short 1J18-5 to either 1J18-6 or 1J18-7. Make sure to this is while in diagnostic mode. If this energizes the solenoid then the problem is further up stream (U49).

Without doing any investigation and having no evidence other than what you have written I would guess that U45 is bad. It is unlikely (but still possible) that U49 is bad. Bear in mind you could be dealing with two problems that might be masking each other (i.e. fixing one problem does not fix the entire issue). Often multiple components in the special solenoid circuitry are taken out by one event.

system11_solenoid_17.jpgsystem11_solenoid_17.jpg
#3 2 years ago

Thanks for the detailed response
Board work is not my strong suit, there is another buddy in our circle who is much better at it...I will pass this along to him...

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