(Topic ID: 192593)

Big Guns left kicker not working

By chinosts

6 years ago


Topic Heartbeat

Topic Stats

  • 19 posts
  • 2 Pinsiders participating
  • Latest reply 6 years ago by zacaj
  • Topic is favorited by 3 Pinsiders

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#1 6 years ago

I recently bought a Big Guns which for the most part is in pretty awesome condition. I only discovered after a couple of games that the Left Outer Lane kicker doesn't fire when the kick back feature is activated. The switch on the lane works OK, just the kicker doesn't move.

I checked the coil with a multi meter and it comes up 4.5 ohms resistance which I believe means its alright.

Any help would be very appreciated.

#2 6 years ago

Does it fire in the coil test? Is there voltage at the coil?

#3 6 years ago

Hey zacaj no it doesn't fire in the coil test.. Any ideas?

#4 6 years ago
Quoted from chinosts:

Hey zacaj no it doesn't fire in the coil test.. Any ideas?

In order for it to fire, it needs to have voltage on one side of the coil, and ground at the other side. 25+V DC should be be present on one side of the coil whenever the game is on. The boards then ground the other side when they want to fire it. You can tell which side is which by looking at the diode on the coil. The banded end is connected to the lug that should have the 25+VDC. The non-banded end is connected to the lug that gets grounded. If the banded side has voltage, then you need to figure out where the failure is on the ground side. It could be a wiring issue, a bad connector, or a problem on the board. The easiest way to check is with a jumper wire/alligator clips, although any wire can be used. Connect one end to ground (there's ground braid running inside the cabinet in both the head and body), and then touch the other end to the non-banded side of the coil. This bypasses the entire chain, so the coil should definitely fire. If it fires then, try touching the wire to the metal tab on the corresponding transistor on the board (Q71, according to the solenoid table in the beginning of the manual). There should be a diagram in the manual of the driver board so you can locate Q71. If grounding Q71 also makes the kicker fire, then you've got a board issue, and you'll probably want to send it off to get repaired if you're not confident soldering. If grounding Q71 doesn't make the kicker fire, then you've got a continuity problem between the transistor on the board and the coil, and you'll need to trace the path through the game, checking continuity with your meter, till you find the problem. It's usually a bad connector, but the wire could also have come disconnected somewhere or broken.

#5 6 years ago

thanks for your help zacaj .. the funny thing is.. The coils on my machine don't seem to have diodes connected as expected. I checked under the playfield as well and I cant see diodes connected to any of the coils. Did Williams do things differently for this era of machine? The coil that is not working has two wires connected to one of the terminals which I believe from my research to be the positive terminal which I guess means the other terminal is the ground?

#6 6 years ago

Hey @Zacaj.. I performed the tests you suggested and I got some results.. grounding the solenoid made it energize and grounding the transistor Q71 also made it energize. Does this mean that I need to replace the transistor? Is so, can you help with what part I need to get and where can I get it from? I am reasonably confident that if I get the correct part I'll be able to solder it to the board. The only scary bit for me is the disconnection and removal of the system 11 board! Cheers for all your help!

#7 6 years ago
Quoted from chinosts:

thanks for your help zacaj .. the funny thing is.. The coils on my machine don't seem to have diodes connected as expected. I checked under the playfield as well and I cant see diodes connected to any of the coils. Did Williams do things differently for this era of machine? The coil that is not working has two wires connected to one of the terminals which I believe from my research to be the positive terminal which I guess means the other terminal is the ground?

Strange, maybe I'm mis-remembering mine. At some point Williams moved the diodes to the driver board. The lug with two thicker wires is normally the positive terminal, yes.

Quoted from chinosts:

Hey Zacaj.. I performed the tests you suggested and I got some results.. grounding the solenoid made it energize and grounding the transistor Q71 also made it energize. Does this mean that I need to replace the transistor? Is so, can you help with what part I need to get and where can I get it from? I am reasonably confident that if I get the correct part I'll be able to solder it to the board. The only scary bit for me is the disconnection and removal of the system 11 board! Cheers for all your help!

Replacing the transistor is a safe bet. It's a TIP122. That won't always be the issue (it could be whatever sends the signal to the transistor) but it's the most common cause.

#8 6 years ago

Hey zacaj .. I replaced Q71 with a new TIP122 transistor but the coil still doesn't fire in coil test or in game and only when I ground Q71 or the coil itself. Any ideas what I should be checking next?

Cheers in advance for the help anyone can give..

#9 6 years ago
Quoted from chinosts:

Hey zacaj .. I replaced Q71 with a new TIP122 transistor but the coil still doesn't fire in coil test or in game and only when I ground Q71 or the coil itself. Any ideas what I should be checking next?
Cheers in advance for the help anyone can give..

I'd check Q71 and its pre-driver with your DMM diode test. You can compare readings across the legs with ones from another working transistor. They should read roughly the same. Hopefully the pre-driver reads wrong, and you can just replace that too. It's possible one of the ICs that drives it is bad though, and finding that might get a bit complicated

#10 6 years ago

Hey again zacaj .. sorry for being such a complete noob.. do you know which component is q71's predriver? In future, how is the best way to identify this component. I have the manual so I'm sure it's in there.. thanks again for all your help!

#11 6 years ago
Quoted from chinosts:

Hey again zacaj .. sorry for being such a complete noob.. do you know which component is q71's predriver? In future, how is the best way to identify this component. I have the manual so I'm sure it's in there.. thanks again for all your help!

You'll need to find the schematics for the board and see which transistor drives it. Probably http://arcarc.xmission.com/Pinball/PDF%20Pinball%20Misc/Williams%20System%2011a%20Schematics.pdf, but some Big GUns have 11b boards instead. It's usually located right next to the TIP122 and numbered adjacently but you can't be 100% sure that'll be the case.

In that PDF, you'll find Q71 on page 12 of the PDF (no real trick to finding it, just look for the transistor symbol (the circle with three lines meeting inside it). Connected to its input is Q70, another transistor (2N4401), and that's the predriver. You'll also see U45 before that which is the IC which controls the pre-driver (which controls Q71, the driver). Usually the possibility of a part being bad decreases the further into the circuit you get, which is why you always try replacing Q71 first. If you've got a oscilloscope or logic probe (or an LED and a wire if you're desperate) you can often watch the signals between each of these components to see where the problem is but drivers and pre-drivers aren't hard to replace either. You can often tell they're wrong with the diode test too, which only sometimes works on ICs.

#12 6 years ago

Thanks heaps.. my local supply doesn't have any 2N4401s and only has 2N3904s.. I can see they are rated to a lower mAmp but apart from that are the same. Do you think it will be ok to use that part instead?

#13 6 years ago
Quoted from chinosts:

Thanks heaps.. my local supply doesn't have any 2N4401s and only has 2N3904s.. I can see they are rated to a lower mAmp but apart from that are the same. Do you think it will be ok to use that part instead?

Looks to me like the 3904 is about 1/3 as good for the amps? I'm not good enough with transistors to say how many amps the pre-driver needs. If you're in a hurry, and the pre-driver definitely tests differently, it's worth a shot? At worst probably you'll just blow it, or maybe the driver too. Might be easier to see if any other 2N4401s on the board aren't used (their corresponding solenoids aren't connected in big guns) and move one. I'd definitely check it with a meter first before getting that adventurous though

#14 6 years ago

I'll give it a go and let you know the results! It's times like these that I wish I had done a Electronic engineering degree instead of IT

#15 6 years ago
Quoted from chinosts:

I'll give it a go and let you know the results! It's times like these that I wish I had done a Electronic engineering degree instead of IT

I'm wishing that every day...

#16 6 years ago

So no luck with replacing the 2N4401 .. my next best is testing the 7402 to see if there is an issue.. any ideas the best way I can do that? I can easily check to see if it's getting power.. but what about if it's sending any signal from pin 4? If I use my dmm by putting black lead to ground and red on pin 4 and just loop the test for that coil do you think that would be a conclusive test? Or even a test at all? My friend St work suggested putting 5v on the circuit after the chip and see if the coil fires.. that way you can rule out it being the 7402.. what would be the easiest way to do that without risking frying my system board?

#17 6 years ago
Quoted from chinosts:

So no luck with replacing the 2N4401 .. my next best is testing the 7402 to see if there is an issue.. any ideas the best way I can do that? I can easily check to see if it's getting power.. but what about if it's sending any signal from pin 4? If I use my dmm by putting black lead to ground and red on pin 4 and just loop the test for that coil do you think that would be a conclusive test? Or even a test at all? My friend St work suggested putting 5v on the circuit after the chip and see if the coil fires.. that way you can rule out it being the 7402.. what would be the easiest way to do that without risking frying my system board?

You can often test these ICs similarly to how you test transistors with the DMM diode test: http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit

I've done the 5V thing before, just took a wire and tapped it on the leg briefly, but I try to avoid sticking live wires into the board when possible.

I'm not sure if you can pick up the pulse from the pin with your DMM, but it's an easy check and definitely worth a shot. An important thing when trying to debug problems like this is that the whole driver section is just the same circuit repeated many times. The 7402 controls multiple pre-drivers, so if you know one of those other solenoids still fires, you can compare your readings on pin 4 with one of the other pins that goes to another pre-driver when that one fires. If you can pick up the pulse to one of those, but not on pin 4, you know there's a problem.

The King's chamber kicker is Q75, which is also controlled by U45, pin 13. Get that one firing repeatedly in test, put your DMM on the pin, see if you get any reading. If so, check pin 4 while firing the kicker, you should get the same reading.

Note however that the problem could be farther back than U45. If you're not getting a signal on the outputs that you know you should be (because you can see it on pin 13, etc), then it could be that U45 isn't getting its input signal (pins 5 and 6). Again, you'll want to try to compare the signals going into 5+6 with the signals going into 12+11. If the input signals are the same, and the outputs are different, then you know it's U45 that's the problem.

#18 6 years ago

hey @zacaj.. well I have conclusively tested that the problem is not with U45 (I replaced it).. and now I am truly stumped... I am looking at the schematic and I am not sure where the signal on pin 5+6 are coming from... This is my first time in the woods so to speak... Grateful for any more help you can give..

Cheers.

#19 6 years ago

Sorry for the late response, was caught up with pintastic...

It looks like the data line that controls the six special solenoids (including the B line in question) comes out at the top right corner of sheet two, where it connects to pin 4 of U49, which is an inverter, so you should always get the opposite reading on its input (pin 3). If the inverter is functioning properly, you'll have to trace back further to... maybe pin 19 or 39 of U41? That part of the schematic is cut off, and I can't find any other copies online :/ You'll have to check both pins with your DMM for continuity to pin 3 of U49. You should also double check continuity from pin 4 of U49 to U45, etc just in case

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