Hesston, KS
Been out of town for work. I'll check this tomorrow when I get home! Thanks!
(Topic ID: 224305)
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Quoted from GRUMPY:With j-19 disconnected and j-18 connected, turn on the power. Take your logic probe and connect it to the five volt and ground test points on the cpu board. Then probe the j-18 connector, all pins should be a high except for 1,6 and 7 as they are not connected. If this is good then probe pin 2 which is SS #3 and then press the left pop bumper skirt, the high should go low each time you press the skirt. Then repeat this for all 3 pops and both slings.
Just getting time to test this out. Forgive me but where are the test points on the CPU? Never done this before I can’t find it in the schematics.
Also, I was able to find in the schematics the circuit that we are working on here and that helps a lot. I noticed that R108 should be 2.7k. When I test it, I only get 1.6k. Is that a problem as well?
R110 should be 68 n? What does that small n looking mark mean? Same for R109, should be 560n.
ZR7 still shows a 0 and all other ZR# are 4.8 K - I definitely think ZR7 will need to be replaced.
Quoted from jag8511:where are the test points on the CPU?
The ground is near the upper left of the battery. The five volt is between U-21 and U-22.
Quoted from jag8511:What does that small n looking mark mean?
It is a poor quality copy of a ohm symbol not a n mark.
Quoted from jag8511:ZR7 still shows a 0
Cut this off the board and retest 1J-18 pin 9 for a high with your probe and then drop to a low when you push on the pop skirt.
pasted_image (resized).pngWhen I test with the probe, the left bumper and bottom bumper test ok. They are both high until I press the skirt and they go low. The top bumper just stays on high and doesn’t change when I press the skirt. I don’t have the coil connected at the moment. Should that matter in that testing? I’m assuming not because I can’t connect the coil without it smoking.
I did cut off SR7 and tested again. Still only getting a high on Pin 9 for the top bumper
Quoted from jag8511:The top bumper just stays on high and doesn’t change when I press the skirt.
Check the adjustment of the switch and see if it is not closing.
Quoted from jag8511:Sorry - it is stuck on LOW - not high.
Yea this is a problem and must be fixed first before any board repair work.
Quoted from jag8511:The switch seems to be adjusted ok.
Quoted from jag8511:However, I’m wondering if it is stuck on low that it means that switch might be bad and stuck on?
This is possible, you can disconnect the orange/blue wire and see if it goes high now.
pasted_image (resized).pngAlso in the pic you will see that there is resistor and cap connected to the solenoid switch, if these are also on your switch the cap may have gone bad causing the switch to be shorted. You can cut one lead of the cap to see if the short is fixed.
Quoted from GRUMPY:You can cut one lead of the cap to see if the short is fixed.
Does the switch need the cap?
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All the replacement switches I find online don't have anything on them as far as resistors or caps.
I'll do the testing you suggested tonight. Thanks!
The cap and resistor together make an RC network to extend the switch close pulse so that a light tap of the skirt from the ball will give a strong hit from the coil. They will not come on a new switch. Since most people just transfer these parts from one switch to another its likely they are original parts. Some people don't transfer the cap and resistor or just cut them off when they are having issues, that's why I asked if your pin has them or not.
Very interesting. I disconnected the diode and tested. Stayed low. Disconnected the cap and tested. Stayed low. Disconnected the blue / orange wire and it still tested and stayed on low. So with the wire completely disconnected it is still testing and staying on low
Ok, look for SR20 resistor pack. It looks like the pic I posted. You will see a white dot on the board, this is pin one. Inside there are 9 resistors which are pins 2-10. Pin 1 is 5 volts and is tied to one side of all the resistors. These packs can crack internally and sever the 5 volts from the resistor. You can test them with an ohm meter with the power off. You check for ohms from pin 1 to 2 then from pin 1 to pin 3 and so on, you should see 4700 ohms or 4.7k ohms.
pasted_image (resized).pngpasted_image (resized).pngQuoted from jag8511:I assume that means that Pin 9 being .10k is a problem?
Sure sounds like it. Is this something you can replace?
Quoted from GRUMPY:Sure sounds like it. Is this something you can replace?
Sure can! - I replaced one on my Jokerz machine (when I didn't have too, before I knew what I was doing)
Does that sound like the source of all of this?
I'll need to replace Zr7 and Sr20 as well as replace everything in that circuit that was probably damaged from the smoking.
I'll have to look at the manual when I get home to get the part numbers but I need to place an order with Marcos anyway. So I'll add these to it.
Off the top of my head.... 
1. TIP102
2. 2n4401
3. 1n5234
4. RESISTOR SIP 10 PIN 4.7K 9R 10 5%
5. 1n4007
Those look correct! I was able to look up all but the zener diode. But that part# is correct. I got these on order and should be here by the weekend I hope! Thanks for all the help! It is so much fun to learn all this stuff. Everything you have said makes sense and will greatly help me trouble shoot in the future. I hope this fixes the bumper issue and then on to the next issue 
I got the parts today. I was able to replace them all on the board. I put the board back in and tested for the high low on the probe and there was no change. It was stuck on low. I hooked the orange/ blue wire back up to the switch along with the cap and diode on the switch and then tested again it was still suck on low. I pulled the board out and tested the SR20 SIP and reading were all over the place on each lead. Luckily I ordered two. So now I have the board back out and I put a new SIP in, just to test without soldering it back in. It is snug enough that it gets connection and again the readings are all over the place. When I test the SIP off the board I get 4.7k on each leg like I should.
When I put the Zener diode in for Zr7 and test it, my DMM beeps. When I test that diode off the board it reads 730 one way and 0 the other. Like it should.
I'm I doing something wrong? Or are there more problems than just the SR20 being bad like we thought?
Quoted from jag8511:I got the parts today. I was able to replace them all on the board. I put the board back in and tested for the high low on the probe and there was no change. It was stuck on low. I hooked the orange/ blue wire back up to the switch along with the cap and diode on the switch and then tested again it was still suck on low. I pulled the board out and tested the SR20 SIP and reading were all over the place on each lead. Luckily I ordered two. So now I have the board back out and I put a new SIP in, just to test without soldering it back in. It is snug enough that it gets connection and again the readings are all over the place. When I test the SIP off the board I get 4.7k on each leg like I should.
When I put the Zener diode in for Zr7 and test it, my DMM beeps. When I test that diode off the board it reads 730 one way and 0 the other. Like it should.
I'm I doing something wrong? Or are there more problems than just the SR20 being bad like we thought?
Depending on what's in circuit, you can't always test components on the board. Anything in parallel with those SIP circuits will cause a different reading. Don't have the manual cracked open so can't say for sure that's your cause. I've done board work for the 18 years I've been in pinball, but sometimes, when you're facing multiple failures, the frustration builds, and you begin to get impatient and possibly will damage your board from multiple component replacements, as the pads will only take so many heat cycles. At that point, I'll wrap it up and send it to a professional who has a test fixture and can diagnose and repair all issues at once...used to be about $90 to repair a WMS System 11 board. Don't know what the going rate is, but might be worth your sanity. Good luck.
Quoted from robertmee:Depending on what's in circuit, you can't always test components on the board. Anything in parallel with those SIP circuits will cause a different reading. Don't have the manual cracked open so can't say for sure that's your cause. I've done board work for the 18 years I've been in pinball, but sometimes, when you're facing multiple failures, the frustration builds, and you begin to get impatient and possibly will damage your board from multiple component replacements, as the pads will only take so many heat cycles. At that point, I'll wrap it up and send it to a professional who has a test fixture and can diagnose and repair all issues at once...used to be about $90 to repair a WMS System 11 board. Don't know what the going rate is, but might be worth your sanity. Good luck.
I agree - I sent my Jokerz system 11 off for repair and might just have to do the same with this one. Then I at least know the whole CPU has been gone over and I shouldn't have problems with it in the future. The going rate these days is about $125. The problems is that it is a 2-3 month turn around 
I'm open for suggestions on who to use that might have a faster turn around.
Quoted from jag8511:I agree - I sent my Jokerz system 11 off for repair and might just have to do the same with this one. Then I at least know the whole CPU has been gone over and I shouldn't have problems with it in the future. The going rate these days is about $125. The problems is that it is a 2-3 month turn around I'm open for suggestions on who to use that might have a faster turn around.
Pay Dr Cheung $220.
Quoted from jag8511:I'm I doing something wrong? Or are there more problems than just the SR20 being bad like we thought?
You are not doing anything wrong, but sometimes the damage is more severe then first thought. U-50 is most likely shorted out. You can cut U-50 pin 5 to see if the switch input line raises to 5 volts as it should be. If it doesn't raise then it can be U-49 or the pia chip that is bad. You will need a very small anvil cutter to do this. Something like this.
pasted_image (resized).pngShould I go ahead and order all the parts in the circuit and then replace them? I'm wondering if everything got shorted and I may still have problems unless I replace them all? That would at least be alot cheaper than sending the board off.
There was a U chip on my Jokerz that was bad, and replacing that fixed my issue. So it very well could be the same kind of deal here.
Why does the Zener diode give a beep on my DMM on the board, but tests fine off the board? I'm not sure I understand that one, and couldn't really find a good answer online.
Still alot to learn
Quoted from jag8511:grumpy
Should I go ahead and order all the parts in the circuit and then replace them? I'm wondering if everything got shorted and I may still have problems unless I replace them all? That would at least be alot cheaper than sending the board off.
There was a U chip on my Jokerz that was bad, and replacing that fixed my issue. So it very well could be the same kind of deal here.
Why does the Zener diode give a beep on my DMM on the board, but tests fine off the board? I'm not sure I understand that one, and couldn't really find a good answer online.
Still alot to learn
Because you can't test a diode in circuit....a diode blocks current in one direction. When you use a meter to test a diode, the meter applies a small current and measures the voltage drop across the diode. In one direction current flows and you see the .7v drop. In the other direction, current is blocked and you read open circuit. Now take the case of a diode across a coil. You won't get the same results because the coil windings provide a circuit path parallel to the diode. So the small current flows around the diode through the coil. It's why you always need to lift one leg of a diode to test, to isolate any parallel circuit paths.
In this particular case you're testing the zener not as a diode but more like a resistor. By using ohms instead of diode test, a working circuit will read @ 5 k ohms. If you are reading 1 ohm then you know that you may have a bad zener diode. When you get a low ohm reading then you are sure something is wrong you can lift a lead of the zener and retest it to know if it's the zener or something in the rest of the circuit causing the low ohm reading. Now if U-50 is the problem and you cut pin 5 and separate the lead in half. This will remove the short and allow this circuit to rise back up to 5 volts. If there is no change then U-50 isn't the problem and you need to test further up stream to U-49 and so on until you have removed the short. When there is a short on a circuit like you have there is no way to separate the components from the short without removing them from the circuit either by removing the part completely or by cutting a pin. A piece like SR -20, you can't cut a lead so it must be removed from the board and once it has been removed you may as well replace it. Now for U-50, if you cut the lead carefully it can be repaired without replacing the chip. Also if you do not power up the coil until all your testing and repairs are completed you will not damage them. Some people get in a bit of a hurry and power the coil on as a test, this will cause them a lot of frustration, money and time. Test with your meter and probe and when is works correctly with them you will be confident that it is repaired the first time.
Ok - that all makes sense. But why does the Zener I replaced beep and is not get a reading while all the other zener's do give a reading? Is is because there is still a short in the circuit somewhere? So when testing it on the board, I will get funky readings on most components in the circuit?
When I get home tonight, I'll look at the whole circuit and order the parts that I need. Since I'm new, I don't mind ordering parts and not ending up using them to have extra parts on hand for the future.
Your meter will always read the component with the least amount of resistance. So if U-50 is shorted and ZR-7 is good and they electrically connected the meter will beep because of U-50.
Quoted from GRUMPY:Your meter will always read the component with the least amount of resistance. So if U-50 is shorted and ZR-7 is good and they electrically connected the meter will beep because of U-50.
Ok! That makes sense. With U-50. I noticed that it has been replaced once already and has a socket on it. When cutting pin 5, do I cut it in half and then I can solder it back on? Or was your suggestion to cut pin 5 assuming that U-50 was soldered straight to the board? I don't mind waiting and just ordering a new IC to replace U-50 so I don't further damage anything.
The components I have not replaced but look to be in the circuit is R-108,109,110, C-74. Is there anything else I'm missing? Or should I hold off on this until I can test out U-50?
Quoted from jag8511:Ok! That makes sense. With U-50. I noticed that it has been replaced once already and has a socket on it. When cutting pin 5, do I cut it in half and then I can solder it back on? Or was your suggestion to cut pin 5 assuming that U-50 was soldered straight to the board? I don't mind waiting and just ordering a new IC to replace U-50 so I don't further damage anything.
The components I have not replaced but look to be in the circuit is R-108,109,110, C-74. Is there anything else I'm missing? Or should I hold off on this until I can test out U-50?
If it is socketed, you can pull the chip out, and carefully bend the pin back, then put the IC back in the socket. It's a delicate operation because too much bending of the pin back and forth can break it off.
Quoted from jag8511:Or was your suggestion to cut pin 5 assuming that U-50 was soldered straight to the board?
Yes I was under the assumption that it was soldered directly to the board.
Quoted from jag8511:The components I have not replaced but look to be in the circuit is R-108,109,110, C-74. Is there anything else I'm missing? Or should I hold off on this until I can test out U-50?
These 4 components rarely go bad. Its best to keep testing until you find the short, then order parts and replace them, followed by a final function test. robertmee is correct in saying you can carefully bend the lead out a bit and then reinsert the chip in the socket for testing.
Well well well! - I was able to bend pin 5 back and put it back into the socket. I then put the board back in and tested. It was high and then went low when I pushed on the skirt. So it looks like U50 has the short. That is a relief!! But, is there something that caused U50 to short? Since it had been replaced already?
Update - I may have spoke too soon. Pin 5 on J18 is now locked on low. I believe this is the lower pop bumper but I'm not sure where in the schematics it diagrams what each of those are. But the lower pop bumper is the only one that isn't testing correctly now. The other pop bumpers and slings all test ok with the probe. I'm guessing U50 is bad and that might just have something to do with it. Eitherway I'll have to replace U50.
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I'm assuming I need the first one. What is the difference between them?
Quoted from jag8511:I'm assuming I need the first one.
Yep. The second chip is a "LS" Low power schottky. I don't think this chip can pass as much current as the STD TTL chip.
Ok! So I replaced U50 and everything tested with the probe how it should! I have not put the J19 connector back onto the CPU nor have I hooked up the coil wires. Wanted to know what the next step would be. Feels good to be making some progress!
Update - Now the lower pop bumper is stuck on again. When I turn on the game with J19 plugged in the coil is stuck. I didn't connect the upper coil yet. But wanted to play a game of pinbot. It is now stuck on low when I use the probe to test. Which had worked fine in the past but now something is wrong with the lower pop bumper. I'm wondering if it is SR-20? Which I just replaced :/
Quoted from jag8511:When I turn on the game with J19 plugged in
Do not connect this until all testing and repairs are completed. This is what causes most people's frustration when repairing.
Quoted from jag8511:I'm wondering if it is SR-20? Which I just replaced :/
Did you check all 6 special solenoid switch inputs, all should be high until you close the switch then they will go low. After all inputs are checked and working, then you need to check the outputs of U-45 (pin 1,4,10 and 13)and U-50(pins 1,and 4). In attract mode all 6 outputs should be low. Then start a game and recheck the same pins and there should be no change.
I replaced U50 with a new chip (I had ordered extra) All 6 special switches now are testing correctly. They are all high until the switch is closed and they go low. U50 pins 1 and 4 are both low. On U45 pins 1,4 and 10 are low but 13 is high. Does that mean U45 needs to be replaced as well? I didn't test by starting a game. Will wait to see what is said about pin 13 on U45 being high.
Quoted from jag8511:Will wait to see what is said about pin 13 on U45 being high.
So check both inputs for this section of the U-45 chip. In attract mode both inputs (pin 11 and 12) should be high.
Quoted from jag8511:I don't understand what attract mode is
Attract mode is when the machine is on but a game has not been started.
Quoted from jag8511:Ok - so now when I check J18 with a probe - the lower pop bumper is stuck on low again...
Do you have the connector J-18 connected to the cpu board? If yes then disconnect j-18 and retest the header pins on the cpu. This will tell you if its on the play field or on the cpu board.
Quoted from jag8511:Which sucks because it was working before I made repairs to the board.
This happen from time to time. Could just be a coincidence. First check the ohms of ZR4. Looking for @ 5k ohms. Double check your soldering of SR-20 pin #8.
Quoted from jag8511:Ok - I took the board off and reflowed solder to SR-20 pin #8 and now it testing high and going low when I press the skirt. Hopefully, that was it.
Now the inputs are good, lets check the outputs one more time. Keep J-19 off of the cpu, J-18 on the cpu, power on and start and game. Now check the outputs of U-45 (pin 1,4,10 and 13)and U-50(pins 1,and 4). All 6 should be low. If this is good then test the base (pic below) of all 6 drivers (Q-69,Q-71,Q-73,Q-75,Q-77 and Q-79) They should all be low. If this is good then set DMM meter to ohms and check the resistance from ground to the collector of each of the 6 drivers, you should see a reading of .600 meg to .900 meg ohms. If you get a low reading, then the driver transistor is bad. If all 6 test good then plug in J-19 while listening for a coil activating. Unplug immediately if you hear a coil lock on.
pasted_image (resized).pngI'm not sure what is going on. U45 pins 1 and 4 are low and 10 and 13 are high. And then went to recheck J18 and the lower bumper doesn't give any reading on the probe. Took J18 off and tested right to the connection on the board and same result. All the other connections on J18 are testing ok. I hope that makes sense. Possibly a loose connection somewhere? Not sure what to check as I did check all the components I replaced when I pulled the board off.
Quoted from jag8511:10 and 13 are high.
Check the 2 inputs for each output. Check input pins 11 and 12 for the output pin 13. Check input pins 8 and 9 for output pin 10.
11-low
12-low
13-high
8- high (I'm guessing this should be low?)
9- low
10-high
And now when I test for the lower bumper on J18 it tests high and then low when I hit the skirt. It seems like it is cutting in and out.
Update - I let the machine run in attract mode for 5 min and now I don't get a reading. So when I first turn it on, it tests fine. After the machine is on for a bit I don't get a reading at all. And don't get a reading on pin 10 at all. Sounds like U45 might be bad?
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