(Topic ID: 285648)

Black Knight coil locking when game started/in test mode


By Atari1977

15 days ago



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  • 15 posts
  • 7 Pinsiders participating
  • Latest reply 1 day ago by Rikoshay
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Manual (resized).png

#1 15 days ago

I was trying to adjust switch for the jet bumper on my Black Knight and forgot to turn it off first. Now I figured I shorted something because the jet bumper coil keeps locking on. It doesn't lock on when the machine starts up, only when a game is started or test mode is entered. I've checked and So far I've replaced the diode on the coil, IC6,7,8,9 and Q4,6 and I'm still getting the same issue. Anyone have a recommendation on what to try next?

#2 15 days ago

Did you verify the switch is not closed or that a wire to the switch is shorted to the coil frame?

#3 15 days ago

Did you check the steel yoke plate as they can crack in half and each half can rotate.

#4 14 days ago
Quoted from Billc479:

Did you verify the switch is not closed or that a wire to the switch is shorted to the coil frame?

I did check to make sure the switch is open, will go back and see if there's any shorting.

Quoted from sixpakmopar:

Did you check the steel yoke plate as they can crack in half and each half can rotate.

I didn't check that but don't think that's relevant to the current issue where the coil is firing/locking on when a game is started.

#5 14 days ago

Disconnect it from the MPU. Test the board. If it's sending power to the pin when it shouldn't it's a board problem. If it's not then it's a problem on the playfield.

#6 14 days ago

I disconnected 2J13 connector, special switches, and it's still firing the jet bumper. Also when I disconnect the special solenoid drive connector, 2J12, the special switches, slingshots, aren't registering in the switch test.

#7 13 days ago

Ok, more testing, I disconnected the coil completely and I'm measuring 40V on the jet bumper at all times when in test mode or during a game. I'm thinking it's an MPU issue but I'm not sure what else to replace since I've basically replaced every part that controls this coil's logic.

#8 12 days ago

Tested the pre-driver transistors in the special solenoid section, I think Q7 might be off.

Also tested the switch matrix just to make sure that the secondary switch wasn't shorted and that was reading the jet jumper's switch row just fine.

#9 10 days ago

Replaced Q7 and Q11, coil is still locking on.

#10 9 days ago

Q5 and Q6 are for the pop bumper. I don't see in your notes where you have replaced Q5 (pre-driver).

Do you have a logic probe?

#11 9 days ago
Quoted from Schwaggs:

Q5 and Q6 are for the pop bumper. I don't see in your notes where you have replaced Q5 (pre-driver).
Do you have a logic probe?

Which manual did you see that in? The copy I have lists Q4 and Q6 for the jet bumper, though I do know Williams manuals are sometimes wrong

Manual (resized).png

Do not have a logic probe.

#12 9 days ago
Quoted from Atari1977:

Which manual did you see that in? The copy I have lists Q4 and Q6 for the jet bumper, though I do know Williams manuals are sometimes wrong
[quoted image]
Do not have a logic probe.

The schematic lists Q5 as the pre-driver and Q6 as the driver. Also, there are 2 solenoids with Q4 listed in that table Q6 is listed twice as well.

#13 8 days ago

Ok, so two things. One I had misread the drive board layout and had actually replaced Q11,Q12,Q7,and Q8.

I went ahead and replaced Q5, Q6, Q3, and Q4. Jet bumper is still locking on.

#14 8 days ago

Because crazy things happen in pinball machines, I keep a Known Working extra board for MPUs and Drivers. Once I have exhausted logic, I bolt one of those in. If it cures the problem at least I know where to start

#15 1 day ago

Is there by chance a capacitor across any pins on the switch?
Are you able to post a pic?

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