(Topic ID: 274975)

Locked coil on System 11 Road Kings


By boneman91

5 months ago



Topic Stats

  • 13 posts
  • 6 Pinsiders participating
  • Latest reply 4 months ago by Nw55555
  • Topic is favorited by 1 Pinsider

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#1 5 months ago

My right kicker coil on my System 11 Road Kings locks on when I enter test mode, as well as when the game is started or any time power gets to the coil.

I got this Road Kings in 2015 that had been left in a bowling alley that closed after a flood in 1991. I've been working on it off and on since then. I refurbed it and got it working well and cleaned up except for this one problem. I Replaced the Q71 transistor. Problem recurred. Sent the board out for repair, came back with a clean bill of health, and problem recurred. Tried replacing Q71 again, still locks on. I've replaced the coil. I've traced both the power and return wire, can't find any issues.

Nobody makes an early System 11 replacement board and mine looks better than the "tested" ones I see for sale at shows.

I'm proud of my refurb efforts and the game is actually pretty fun to play, but this coil issue is ruining my accomplishment! I'm at the point now where I'm ready to remove the coil and just play with a dead bumper unless you guys have any ideas.

#2 5 months ago

Isn't isn't there a pre driver transistor before the Q 71?

#3 5 months ago

I think so. Its a small three prong thing. I think I replaced that a while ago. Should I try again? How can I test it? I've tried following the directions on the System 11 repair guide, but my DMM doesn't have a "tone" setting for Ohms, and my DMM never reads zero for ohms like the guide says for a bad transistor. I'm an electricity noob, and an totally confused by the DMMs.

#4 5 months ago
Quoted from boneman91:

I think so. Its a small three prong thing. I think I replaced that a while ago. Should I try again? How can I test it? I've tried following the directions on the System 11 repair guide, but my DMM doesn't have a "tone" setting for Ohms, and my DMM never reads zero for ohms like the guide says for a bad transistor. I'm an electricity noob, and an totally confused by the DMMs.

You test transistors with the diode setting. Generally, the larger ones get black lead on center and red lead on the outside legs. Should read .4 to .6. Swap that to red lead on center and black lead on the outside for the predrivers (smaller transistors). Should get the same readings. Have you verified that one of the activating switches is not closed? Maybe a solder blob or a shorted switch cap? Place a piece of paper between both switches to ensure the contacts are not touching. Clip off one end of the switch cap if it still locks on.

#5 5 months ago

I have checked the switch contacts, and they are not triggering. No solder blobs noted on the switches. How do I test the switch capacitor? Sorry for being so clueless on electricity. That's the only thing I haven't checked. I have been getting the .4 to .6 readings on the Q71. Will check the pre-drivers. Thanks!

#6 5 months ago
Quoted from boneman91:

Nobody makes an early System 11 replacement board and mine looks better than the "tested" ones I see for sale at shows.

I have reproduction / replacement boards for System 11 but it's only documented in my thread. I have not made them widely available but I do have them and they do work (there was one my friend with a High Speed was borrowing while I repaired his board).

Quoted from boneman91:

My right kicker coil on my System 11 Road Kings locks on when I enter test mode, as well as when the game is started or any time power gets to the coil.

If the solenoid locks on immediately at power on then the transistor is shorted. If the solenoid locks on when starting a game (or entering diagnostic tests) then suspect the path where the logic from the software and the hardware merge at the digital logic level. You should exclude the switched (special) solenoid switch. Disconnect 1J18 and repeat the tests. If the solenoid still locks on then the problem is likely in the digital logic side (upstream from the drive transistors). If the solenoid does NOT lock on then it's likely to be a playfield switch problem. Always consult the schematic in the manual for confirmation.

Quoted from boneman91:

I Replaced the Q71 transistor. Problem recurred. Sent the board out for repair, came back with a clean bill of health, and problem recurred. Tried replacing Q71 again, still locks on. I've replaced the coil. I've traced both the power and return wire, can't find any issues.

If the solenoid diode has failed you will continue to replace the transistor until you replace the diode. The diode stops the back EMF voltage spike that causes the transistor to fail.

#7 5 months ago

Can i ask where you sent it for repair?

#8 5 months ago

Thanks DA, will try your suggestions.

Blackbeard, can't remember at this time. Somewhere in the nidwest I think. Got the link from pinside here. It was maybe 4 years ago. I left the hobby for a few years , and just coming back. Went back to my other love, woodworking, where annoying electrical problems don't exist. Now trying once again to get some project machines up and running.

#9 5 months ago

DA, I did as you suggested, disconnecting IJ18 and the lock on persisted. It did not lock when I turned the power on, but did both on starting a game and testing. So it is upstream from the transistors. How do I fix ir on the logic side? Do I replace U25?

Thanks for your patience.

#10 5 months ago
Quoted from boneman91:

DA, I did as you suggested, disconnecting IJ18 and the lock on persisted. It did not lock when I turned the power on, but did both on starting a game and testing. So it is upstream from the transistors. How do I fix ir on the logic side? Do I replace U25?

Right kicker is switched (special) solenoid #2 (solenoid #18).

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Drive transistor Q70 is switched by digital logic 7402 at U45.

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Software input to 7402 at U45 is 7407 at U49.

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Software input to 7407 at U49 is 6821 at U41.

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You will have to trace the signal. The signal is static so you should be able to measure the voltage and compare for differences against the other pins in the circuit.

#11 5 months ago

Great explanation on these things dumbass. I read thru a different explanation you posted for a similar issue on a millionaire (which I now own).

Thanks for taking the time to help others on here. It is appreciated.

#12 5 months ago

Thanks DA. Will try to get on it this weekend.

1 week later
#13 4 months ago
Quoted from boneman91:

Thanks DA. Will try to get on it this weekend.

How did you make out? I have this exact same issue on my Bad Cats(11B), except it is the left kicker. Transistor tests fine, can't find any other issues. Like you, novice on the electronics piece.

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