System 7 (Black Knight) flipper problem...


By MoSeS_1592

1 week ago


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#1 12 days ago

So I was playing my Black Knight today and the left upper and left lower flippers suddenly stopped working mid-game. Everything else works just fine, including both upper and lower right flippers.

Before I start troubleshooting the issue could someone give some advice on where to start looking or if there is a most-likely culprit to look for first? I figure it cant be a fuse or a relay since the right side flippers work, and it can't be a burned out coil since both left flippers went out at the exact same time. From what I gather the flipper coils don't use the TIP102's like the other coils (correct me if I'm wrong). I am not very familiar with System 7 hardware, so any advice that may narrow down what to look for and save time diagnosing the problem would be greatly appreciated.

Thank you!

#2 12 days ago

Wire test. Any broken .?

#3 12 days ago

I'd check fuse anyway.

LTG : )

#4 12 days ago

Do you get voltage on the lower left flipper ? Documentation on IPDB is pretty unreadable, but if voltage does not come to the lower one, the upper one is dead as well. Is it one single fuse for left and right flipper or is there one per side ? I agree with LTG and chad about broken wire or fuse.

#5 12 days ago

I'll check and report back. Thanks!

#6 12 days ago

Biggest suspects are the wires to and from the cabinet switches, the playfield to backbox connector, and the relay on the driver board.

#7 11 days ago

There is only one relay for all four flippers and it is functioning normally. I checked all fuses just to be safe (but all four flippers share one fuse) and all are fine. I checked voltage on the dead coils and its zero when the flipper button is pressed and when not pressed. I did not see any loose wires or cracked solder joints.

Is there something else on the driver board to look for? Where exactly do the flippers get their power? I know the flippers and buttons connect to the driver board but is there a set of driver board transistors in that circuit or is the driver board simply a pass-through (aside from the relay) to the power supply board? I suppose what I am asking is if there is any other hardware on the driver board (aside from the relay, solder joints and connectors) that need to be checked.

At this point do I assume its a physical break somewhere in a wire, connector, solder joint?

#8 11 days ago

Check continuity from where the power goes into the driver board to where it comes out, while in a game. It just goes connector to relay to connector, but it's possible one side of the relay isn't making contact anymore

#9 11 days ago

There is indeed only one relay and one fuse. However, there are separate ground wires from the driver board and separate power wires from the power supply. One for left and one for right. The only circuitry for flippers on the driver board is the relay. It cuts the ground side of the flipper circuit when not in a game. The positive power side of the circuit comes from the power supply board. Since some flippers and coils are working, we know the problem is not with the power supply itself.

Start by checking the connector and pins on J12. It is the second connector from the top on the left side of the driver board. Pins 1 and 2 (pin 1 is the bottom pin) are the flipper grounds and pin 2 is for the left side. Check for burning, loose wires, bad IDC connection and reflow the solder on the pins on the board.

The power supply also has 2 wires, one for left and one for right. These leave the powersupply on J3, the left most connector on the bottom side of the power supply board. Flipper power is pins 4 and 5 counting from the right. Check for burning, loose wires, bad IDC connection and reflow the solder on the pins on the board.

If both board connections are good, follow the wires from the driver board and the power supply board to the connectors between the head and cabinet and check the pins are in good shape and the connector is pushed together all the way.

#10 11 days ago

Also, a trick to determine if the problem is with the power side or ground side of the flipper circuit is if the left magnet works, you know the power side of the circuit is working. If it doesn't work, you should check the magnet fuse, test again, if the magnet still does not work, focus on the power side if the circuit first.

The flippers and magnets share the same power feed wires from the power supply board.

#11 11 days ago

Thank you for the detailed advice, I will check this out tonight and report back.

#12 11 days ago

As usual, Schwaggs is completely on point. I only wanted to add that it's worth reflowing solder to the header pins (or replacing header pins) and re-pinning the connector on the power side of the circuit (located on power supply board at J3) regardless if the source of the problem is there. I was tearing my hair out trying to fix a flipper problem on my buddy's BK. Rebuilt everything, all new flipper cab switches, eos switches, at least one new coil, etc etc...still not working. I was so focused on the ground side that i never bothered to check the power side. Note: i was measuring about 28v or so at the coils, which led me to believe the problem was on the ground side. Anyway, once i finally re-flowed the solder to the header pins at connector J3 on the power supply board--bam! All flippers started working, and were noticeably stronger than they'd been previously. Excited by my finding, i grabbed the power supply board out of my own BK and did the same thing. Well, in my case i replaced the male header pins at J3 (instead of re-flowing the ones) and re-pinned the female connector. Without a doubt, the flippers are definitely more powerful than before! By doing that, at very least you can eliminate any future trouble from that connector, and at best you might get similar results as i did (or it may fix the current issue)...good luck!

#13 11 days ago
Quoted from frunch:

As usual, Schwaggs is completely on point. I only wanted to add that it's worth reflowing solder to the header pins (or replacing header pins) and re-pinning the connector on the power side of the circuit (located on power supply board at J3) regardless if the source of the problem is there. I was tearing my hair out trying to fix a flipper problem on my buddy's BK. Rebuilt everything, all new flipper cab switches, eos switches, at least one new coil, etc etc...still not working. I was so focused on the ground side that i never bothered to check the power side. Note: i was measuring about 28v or so at the coils, which led me to believe the problem was on the ground side. Anyway, once i finally re-flowed the solder to the header pins at connector J3 on the power supply board--bam! All flippers started working, and were noticeably stronger than they'd been previously. Excited by my finding, i grabbed the power supply board out of my own BK and did the same thing. Well, in my case i replaced the male header pins at J3 (instead of re-flowing the ones) and re-pinned the female connector. Without a doubt, the flippers are definitely more powerful than before! By doing that, at very least you can eliminate any future trouble from that connector, and at best you might get similar results as i did (or it may fix the current issue)...good luck!

Wow, that is a lesson for sure! I totally agree with you. I rarely reflow solder on these 35+ year old machines. On my personal machines, I always replace the header pins on all my boards. It is the best option but some people don't have them on hand so re-flowing solder is the next best thing.

I have one for you. I was beating my head against a rock trying to get the flippers to work AT ALL on a newly acquired BK. Measured voltages at the coil - good. Good connectivity back to the driver board. With the flipper held in, read 28V at the driver board not in a game (relay not energized). As you push the flipper button, you would see 28V on and off. So the wiring had to be good from the power board to the driver board. It had to be the connection on the driver board... So I replaced header pins and repinned the connector at the driver board. Nothing. Not even a little movement.

In a moment of frustration, I started repeatedly pushing (beating ) the flipper buttons and after a few seconds, the lower right flipper started working... WHAT??? I kept pushing them over and over and the lower left started working, then the upper flippers started working one by one. The flipper button contacts must have been oxidized enough to measure closed but when power was applied, they didn't pass current. Solution was to repeatedly open and close the flipper button contacts, removing the oxidation.

#14 10 days ago
Quoted from Schwaggs:

Solution was to repeatedly open and close the flipper button contacts, removing the oxidation.

Man, if only every fix was that simple... I'd probably check everything else first and hours later realize it was something simple like that

Glad to know I'm not alone!

Btw, i really enjoy following your tech posts--I've watched you fix several games via pinside over the past few months and it's always a helpful, educational experience. Keep up the good work, man!

#15 10 days ago

I tried flowing fresh solder to all the pins on J12 and J3 and to all solder points on the relay with no luck yet. Just curious, to rule out a bad relay could I use a piece of wire and temporarily short the two leads that the relay normally closes during play, essentially bypassing the relay? This would have the effect of making flippers operate even in attract mode, right? Does anyone know which two pairs of leads to short under the relay to accomplish this? If not I suppose I could Google up a data sheet on that relay. I believe the next (easiest) thing to narrow down is checking continuity of the circuit .

Oh, and both magnets do still work.

#16 10 days ago

Just to be sure, did you also re-pin the female connectors that pair with the headers you re-flowed?

The relay can be bypassed, but I'll leave you in Schwaggs capable hands for exact directions. I suppose the transistor that activates the relay may also be a possible suspect, but I'll step aside now and let the pros take over. You'll have this up and running soon, I'm sure! Good luck!

Edit: there's also a way to ground the flipper coils directly with a jumper wire (i keep a jumper with alligator clips on each end for this purpose)--attach one end of the jumper to the flipper coil at the lug with the *non-banded* side of the diode (the ground side) and very briefly touch the other end to one of the metal side rails or to the ground braid. If the flipper fires when you do that, it would appear to be an issue with the ground side of the circuit.

#17 10 days ago

I'm not sure how to describe the pins of the relay itself, but you can start but jumping the connector. Connect 2P12-2 to ground with alligator clips or something and see if the coil works. If so, follow the trace from that pin on the connector to the relay.

#18 10 days ago

I'll try both of these methods and report back the results. Thank you for the advice! And no, I did not yet repin the female connectors (yet).

#19 10 days ago
Quoted from frunch:

Man, if only every fix was that simple... I'd probably check everything else first and hours later realize it was something simple like that
Glad to know I'm not alone!
Btw, i really enjoy following your tech posts--I've watched you fix several games via pinside over the past few months and it's always a helpful, educational experience. Keep up the good work, man!

Thanks for the kinds words! I really love fixing these things and getting them back to reliable operation. I love it so much if I can do it vicariously through others, it is almost as fun!

Quoted from MoSeS_1592:

I tried flowing fresh solder to all the pins on J12 and J3 and to all solder points on the relay with no luck yet. Just curious, to rule out a bad relay could I use a piece of wire and temporarily short the two leads that the relay normally closes during play, essentially bypassing the relay? This would have the effect of making flippers operate even in attract mode, right? Does anyone know which two pairs of leads to short under the relay to accomplish this? If not I suppose I could Google up a data sheet on that relay. I believe the next (easiest) thing to narrow down is checking continuity of the circuit .
Oh, and both magnets do still work.

Cool, we know the power side of the circuit is solid and can focus on the ground side.

I took a look at one of my spare driver boards and confirmed the relay has 4 sets of contacts, 2 are used for each side of the flipper. I have no idea why Williams didn't tie all 4 relay contacts together... anyway....

If you want to rule out the relay, one way would be to remove the connector from the board, insert a small piece of solid conductor wire (around 18 gauge I think would match the diameter of the header pins) in pins 1 or 2 of the connector, and tie the other end of the wire to ground in the backbox.

Have a quick look at the left side flipper button in the cabinet. Make sure the wires are soldered on securely and that the switch looks no worse than the other side. They can be quite rough looking and still work fine.

Since your flippers stopped working mid-game, I doubt the problem is the relay and would suspect a bad connector somewhere.

#20 10 days ago

So just to clarify, the wires for pins 1 and 2 on the J12 (female) connector can be temporarily connected to ground, and this should essentially bypass the relay, which means that pressing the flipper button should (under normal circumstances) trigger the flipper, even in attract mode, correct? And if this does happen then there is a possibility it could be the relay or something upstream between the J12 female connector and the power supply board (ruling out under-playfield problems), correct?

And if I were to ground the (non-banded) lug on the coil itself and it worked, then I'd know that the problem is simply on the ground side, not as specific as testing the pins 1 and 2 first, correct?

The flipper button looks fine, solder connections very solid.

#21 10 days ago
Quoted from MoSeS_1592:

So just to clarify, the wires for pins 1 and 2 on the J12 (female) connector can be temporarily connected to ground, and this should essentially bypass the relay, which means that pressing the flipper button should (under normal circumstances) trigger the flipper, even in attract mode, correct? And if this does happen then there is a possibility it could be the relay or something upstream between the J12 female connector and the power supply board (ruling out under-playfield problems), correct?
And if I were to ground the (non-banded) lug on the coil itself and it worked, then I'd know that the problem is simply on the ground side, not as specific as testing the pins 1 and 2 first, correct?
The flipper button looks fine, solder connections very solid.

Yes on both accounts.

Grounding the lug on the coil would confirm the flipper coil and everything back to the power supply board is good.

Grounding at the J12 female connector would confirm the ground wiring, flipper switch, etc are all working and would isolate the problem to the driver board.

#22 10 days ago

I read most of this, since new headers were put in, and since we have one side working, I suspect broken pins in the female connector on PS(idc, sorry if you already replaced) , or issies with contacts at the switches. the relay contacts could be suspect but I think the other issuws are more likely (broken wire, broken pin, bad solder joint)

#23 10 days ago

Thanks for the info. I will do the grounding test tonight and check continuity on the PS connector pins again just to be sure and will report back.

#24 10 days ago

Another clarification if you don't mind (pardon my ignorance here), the positive wires for the flipper coils go DIRECTLY from the power supply board to the flipper coils via power supply connector 3J3 pins 4 and 5 WITHOUT ever going through the driver board, correct? Now, if this is correct, then the magnets also feed directly off of 3J3, pins 4 and 5 as well, correct? And, like Shwaggs said, the positive circuit must be fine, otherwise the left magnet wouldn't work. Is this all correct?

Also, if I place a voltmeter on the banded side of the coil lug and also to ground, I should ALWAYS get a 40-50v reading, correct?

#25 10 days ago

They are fed off the same line as the magnets, yes. 3J3 -> 8P2 -> upper flipper -> 8P5 -> lower flipper+magnet.

You should always get voltage there, yes, but it might not be that high, probably closer to 30V.

#26 10 days ago
Quoted from zacaj:

They are fed off the same line as the magnets, yes. 3J3 -> 8P2 -> upper flipper -> 8P5 -> lower flipper+magnet.
You should always get voltage there, yes, but it might not be that high, probably closer to 30V.

Agreed.

The power side of the flipper circuit doesn't go through any boards once it leaves the power supply board.

Since the left magnet works, you DO NOT have a problem with the power side of the circuit (power supply itself, pin, connectors, etc). Your problem is on the ground side.

#27 10 days ago

Ok, so I checked the voltage at all three lugs on the flipper coil and each reads around 30-35V AC. I directly connected both orange wires (Pin 1 and 2 from J12) to ground. When I do this the right flippers function even in attract mode, as expected. But I still get nothing on the left flippers. I'm assuming now that the problem is somewhere under the playfield. I again verified continuity in the female connector where the orange wire engages the crimping plate in the connector and it is fine. I also tried triggering the flipper button by using a wire to short the flipper button lugs together in order to rule out oxidation trouble on the contact points. No dice there either. I guess my next question here is, if I want to start checking continuity under the playfield, where would I start?

If I put my continuity tester on the J12 Pin 2 orange wire where it engages the J12 female connector, then where, under the playfield, does this wire directly connect to so I can test that and at least narrow that down and make sure the wire isn't broken?

Also, would it be wise to unplug and re-plug in all of the major wire harnesses that connect the backbox wiring to the playfield's nervous system in the event that the problem could be there?

Come to think of it I did recently have the playfield propped up vertically against the backbox while I was replacing a dead drop target solenoid. I was very, very careful not to stretch any wires but who knows if something jostled loose.

#28 10 days ago

If grounding J12 doesn't do it, then you've got a problem between J12 and the flipper. The chain is: 2J12-2 -> 7P1-9 (inline to the lower cabinet) -> flipper buttons -> back through 7P1 -> 8P3 (inline) -> upper playfield. Note however that it splits at the flipper buttons as there is a separate button for the upper and lower flipper, so your problem is most likely between 2J12 and the flipper buttons.

As an extra test, try grounding the lugs on the left flipper buttons while in game. If they flip then then that'll narrow down the problem. At that point, just start checking continuity across each of the mentioned connectors.

#29 10 days ago

Just got a few more clues... I was messing around trying to trace the J12 Pin 2 orange wire. I disconnected the major harness I expected the wire to go to and started checking for continuity. All the while I had electrical tape over the flipper button. I got a beep when I stuck the tester in the backbox side of the harness where a dark gray wire comes out. It didnt make sense since I was looking for an orange wire, then it dawned on me to take the tape off of the flipper button. See the photo below. When I connect my tester to this harness and to the orange Pin 2 wire, when I press the flipper button (with the machine OFF) my tester beeps.

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#30 10 days ago

Zacaj, I will try this, thank you.

#31 10 days ago

Unrelated question, but just below the connectors in the photo I just posted there is a (non-functioning) cooling fan mounted between the cab and the backbox. Is that original or did somebody add that later on?

#33 9 days ago

Tried grounding the flipper switch lugs and got nothing

#34 9 days ago

Will keep checking through the chain and report back.

#35 9 days ago

Dumb question but how do i identify which connectors are 7P1 and 8P3, I see reference to those connectors but don't see a way to identify them

#36 9 days ago

Only way I know is by the colors of the wires. I assume they had labels originally but I've never seen them.

#37 9 days ago

Agree, wire colors. I usually trace the wires colors from the board connector, follow the group of colors through the backbox harness to the connector.

#38 9 days ago

I’ve done some more narrowing down and must say I am confused. As of now here is a comprehensive list of everything confirmed so far:

Continuity good between J12 and flipper button middle/ground lug.

Continuity good between the other two flipper button lugs and the two female pins of the 36-pin black connector in backbox.

Continiuty good between flipper coil lugs (middle and non-banded side) and the two male pins of the same 36-pin black connector in backbox.

Continuity good between the coil lug on the banded side of the diode (gray wire) to the connector at J3 on the power supply.

A few more observations:

If I tape down the flipper button (with machine off) I get continuity from J12 all the way to the female pins of the 36-pin back connector in the backbox.

As was suggested I used a jumper to briefly connect the non-banded side of the left flipper coil to ground (while in game play). This resulted in nothing. It did not activate the coil. To make sure I was doing this correctly I tested the same thing on the right flipper (which works fine) and grounding the non-banded lug did not activate that flipper either. I do not understand why this didn’t work.

I still read around 30 volts on both left and right LOWER flippers and 50 volts on both of the UPPER pf flippers. I’m not sure why.

I am at a loss here. Could one bad coil on the left side cause the other left coil to stop working?

#39 9 days ago

If you unplug the lower playfield from the upper does the upper left start working?

You say you get continuity to the big black connector, but do you get continuity across it?

When grounding the coil, can you fire other non flipper coils using the same method? Are you sure your ground is good?

#40 8 days ago

Well, for anyone interested I finally figured it out. I had a twofold problem. zacaj asked if the ground was good. I never thought in a million years it could be that, but after checking it the ground wire was not connected to under the cabinet. Only the backbox was properly grounded. This explains why directly jumping the coil lugs to the cab's ground didn't work. I grounded the cab and the right flippers fired when I jumpered its lug to ground. This worked for the right flippers but not the left. Upon re-checking the voltages I realized that I was getting obscure readings since I was checking + against an open cabinet that was not grounded. For some reason my voltmeter only showed a voltage on AC mode when the cab ground was opened when I checked the left flippers. Anyways, after properly grounding the cabinet, I came to realize that I did NOT have voltage going to the left flippers. I again traced the gray (+) wire from the left coil lug up to J3, Pin 5. When I disconnected the connector from the PS and pressed the tester against the wire where it engages the pin inside the female connector, i got a good reading. When I connected it to the PS and checked for continuity to the flipper fuse harness, I got nothing. Turns out it the J3 male pin 5 solder was cracked. I got so confused because with the cabinet not being grounded I was, for some strange reason, getting a good AC voltage reading on all three lugs for the left flippers. This let me to believe I had voltage going to the coils (even though I was almost certain it should've been DC and not AC).

Thank you guys so much for the advice. I learned a lot through this experience and fortunately it ended up being an easy fix, plus I fixed a dangerous grounding problem I was unaware of.

#41 8 days ago
Quoted from MoSeS_1592:

Well, for anyone interested I finally figured it out. I had a twofold problem. zacaj asked if the ground was good. I never thought in a million years it could be that, but after checking it the ground wire was not connected to under the cabinet. Only the backbox was properly grounded. This explains why directly jumping the coil lugs to the cab's ground didn't work. I grounded the cab and the right flippers fired when I jumpered its lug to ground. This worked for the right flippers but not the left. Upon re-checking the voltages I realized that I was getting obscure readings since I was checking + against an open cabinet that was not grounded. For some reason my voltmeter only showed a voltage on AC mode when the cab ground was opened when I checked the left flippers. Anyways, after properly grounding the cabinet, I came to realize that I did NOT have voltage going to the left flippers. I again traced the gray (+) wire from the left coil lug up to J3, Pin 5. When I disconnected the connector from the PS and pressed the tester against the wire where it engages the pin inside the female connector, i got a good reading. When I connected it to the PS and checked for continuity to the flipper fuse harness, I got nothing. Turns out it the J3 male pin 5 solder was cracked. I got so confused because with the cabinet not being grounded I was, for some strange reason, getting a good AC voltage reading on all three lugs for the left flippers. This let me to believe I had voltage going to the coils (even though I was almost certain it should've been DC and not AC).
Thank you guys so much for the advice. I learned a lot through this experience and fortunately it ended up being an easy fix, plus I fixed a dangerous grounding problem I was unaware of.

Congrats on figuring that one out. One question, how on earth did the left magnet work if it wasn't getting power from the broken solder joint?

#42 8 days ago

I was mistaken when I told you the magnet worked. The magnet solenoid, controlled by a driver transistor worked and clicked. I mistook this for the magnet working.

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