Stellar Wars - bumper not working

Leinhit

New member
Joined
Oct 18, 2006
Messages
5,212
Reaction score
7
Location
Michigan
Prior to posting.. I have been reading and using the repair guide on pinrepair.com

The lower right bumper is not working (I'm not 100% sure it ever was since this is a new to me game..) If I read right.. this is the ONLY special coil on this game that is controlled by the driver board rather than a purely electro/mechanical response to the switch like the others?

I followed all the advice in the guide to the point I have a question..

1. I can get the coil to fire touching the unbanded coil lug to ground.

2. I can get the coil to fire by locating the corresponding TIP122 Transistor on the driver board and touching the center leg to the backbox ground.

3. Then the guide says to test the TIP120 (TIP122 on mine) transistor by using DMM black lead to center tab, and Red to either leg. I "should" get .4-.6 volts.

* Well, IF I have my DMM on correct setting, DCV 200, I get -35 one one leg (black dmm lead to center, red to either side leg) and -35 on the other leg.

Obviously not the same as .4-.6 , as a test I tried some of the other TIP122 next to it.. same readings.

So then..

4. I try the 2n4401 pre driver for this transistor.. IF I got the right thing.. the little transistor right above the TIP120??

I "should" get .4-.6 with Red DMM lead to center and black to either leg..

I "get" -4.8 on one leg, and -.2 on the other. Again as a test, I try some of the neighboring ones.. same thing.

On both of the above transistors, I try some others further away and get completely different readings... (maybe those transistors don't fire coil bumpers but other things that have different readings? maybe?)

So.. my questions.. do I have my DMM on correct setting.. DCV 200 ? (using DCV20 max's out)

Are my readings correct ?

Should I just replace both of those transistors and go from there? Or can someone advise something else to figure out whats wrong.. ?

The guide says after testing / replacing them... I need to go to the 7408/7402 chips and solenoid PIA (pain in ass?)

Thanks in advance.. :)
Steve
 
Last edited:
well..

game off, and DMM on diode setting..

I get on the TIP120 314 one leg / 555 the other leg.. guide says .4-.6 should be the reading.. which would be close IF I put a decimal point in front of my readings (what that be correct in assuming I do)? or is .314 so far off of .4 that it would be bad?

and on the 2n4401.. I get a reading of 555 one leg, and 640 on the other leg.. again correct for .4 - .6 if I put a decimal in front.. correct ?


The next step says to test the 7408/7402 driver chip.. The 7402 is for the 'special' coils.. It doesn't say which chip drives that bank of transistors.. but there is only one 7402 chip in the area.

it says to put test red lead on #7 pin.. NEWB question.. how do I count to the #7 pin? #1 pin above the notch side and count across to the right? Again I'm looking for .4 - .6 readings...
 
Last edited:
ok..

IF I got the red lead on #7 pin of the 7402/7408 chip.. I tried ever one of them on the driver board.. actually found TWO of the chips for the 'special" coils..

They all seem to test with in specs.. .4-.6 I would get most 6XX , again assuming I put a decimal in front of my readings..

It would HELP alot if I knew exactly which chip was the driver for those transistors.. but I tried them all..

Now , unless someone can see something bad in what I've found so far...

I'm back to either the transistors are bad? ... or on to yet another step..

What about the triggering switch itself ?? whats a good way to test it ?.. I press it together to trip the coil and nothing happens... Maybe I need to find out about the triggering switch before replacing transistors, etc...
 
Sorry if you mentioned this already but have you actually tested the driver transistor?

EDIT: Yeah you did mention that. I'll actually take the time to read the thread and make another edit :)
 
Following the steps from pinrepair.com

http://www.pinrepair.com/sys37/index3.htm#trans2


I up to the point of testing the PIA...

I'm following the steps... not sure 100% I understand the results..

I just got back to wondering about the actual trigger switch...

seems complicated for the trigger switch to send a signal to the driver board and then back to the coil...

seems like they could just have the switch go direct to the coil below it...
 
Have you confirmed that the problem is not on the switch side of things? I would definitely check that first.

If we're talking about a "special" coil it won't be driven by a PIA. The drive circuit will be "turned on" by the switch at the pop bumper.

If you want to test the whole drive circuit on the driver board you can ground the pin on the driver board coming from that switch. You'll have to look at the schematic to determine which pin that is. Or you could check the wire color and find it that way, double checking with a meter to be sure you're correct.

If that energizes the coil you know you have a problem in the switch side of the circuit.

EDIT: The game will have to be booted and ready to play for the test I mentioned above to work.
 
Last edited:
Isn't that the test when I grounded the transistor on the drive board and it fired the coil? That indicates to me that the wiring and connections from that transistor to the coil is good at least...


Which , I agree with you.. I started thinking back to the switch..

I did try to touch the two lugs of the switch together with a wire and nothing fired... let me go back and look at the switch closer to see if another test will tell me anything..

I was following the repair guide in all the tests I did so far... including grounding the transistor on the drive board to fire the coil...

the next steps were testing the transistors and that chip I mentioned... according to the guide..

still, I agree with you.. I'm not 100% satisfied I looked at the switch enough to trust it works...
 
Have you put it in test mode and see if it fires. Also, there should be a cap on the pop bumper's switch. Those can go bad and cause it to not work. I'm pretty sure pinrepair talks about these.

Edward
 
Ed,

test mode does not seem to work on my machine.. at least when I was trying to use the buttons / switch on the coin door last week to set some settings.. i.e. number of balls and reset the high score... I can to the conclusion it wasn't working, although the wiring looks good.. not all hacked up.. I also admit the directions to change the setting was confusing to me..

I do know when I tried.. nothing in the displays changed..


I would be interested in trying the test mode tho..

I just looked at the switch and was messing with it... This 'cap' you mention.. is it actually a diode on the switch ? seems to be ok testing with DMM.. reading one direction, but not the other..

Question:.. if grounding the coil makes it fire.. why dont they just have the switch go to one lug of the coil and the other to a ground to fire it?

the wiring from the switch goes deep into other wire harness... whats a good way to test it other than using a wire as I have to jump the switch lugs? maybe I need to find the wire from the switch and see where it comes out and check for continuity? any idea where it goes to without pulling all those wire harnesses apart? both lugs that is?

I also tested the switch lug on DCV and got about 5 volts on the one side..
 
Have you confirmed that the problem is not on the switch side of things? I would definitely check that first.

If we're talking about a "special" coil it won't be driven by a PIA. The drive circuit will be "turned on" by the switch at the pop bumper.

If you want to test the whole drive circuit on the driver board you can ground the pin on the driver board coming from that switch. You'll have to look at the schematic to determine which pin that is. Or you could check the wire color and find it that way, double checking with a meter to be sure you're correct.

If that energizes the coil you know you have a problem in the switch side of the circuit.

EDIT: The game will have to be booted and ready to play for the test I mentioned above to work.

I thought the guide said that the special coils were fired by the driver board ? or is that not the same as the PIA ?

going to go try something...
 
Okay... I think I misunderstood. Unlike most pop bumpers in Williams games this pop bumper is NOT driver by a "special solenoid" drive circuit.

In that case my advice above will not be relevant.

Try the solenoid test. If it works you probably have a switch problem.

I'm leaving the stuff below because it's actually some good information. Just not relevant here:

Isn't that the test when I grounded the transistor on the drive board and it fired the coil?

No. Similar but not the same test at all. That's only testing the connection from the base of the transistor to the coil. The test I suggested tests the 7408 (the AND gate letting the MPU "turn on/off" the special solenoid driver inputs), The 7402 (the NOR gate letting the MPU "turn on" the pre-driver transistor, and the driver transistor. Not to mention the physical connection between the Molex header and the pin on the AND gate.

If the coil energizes in test and not with this test you can suspect the 7408.

[That indicates to me that the wiring and connections from that transistor to the coil is good at least...

Yep... that's all it tests. Since you've established that you can now test the rest of the components. Manually grounding the input is a quick way to test all the stuff.
 
Last edited:
I thought the guide said that the special coils were fired by the driver board ? or is that not the same as the PIA ?

You have a lot of reading to do, my friend.

The driver board is just that, a big board that drives stuff.

A PIA (peripheral interface adapter) is an IC (on the driver board) the accepts commands from the CPU and drives it's outputs accordingly. That's an incredibly simplified explanation but the concept is correct.
 
Try the solenoid test. If it works you probably have a switch problem.

The test I suggested tests the 7408 (the AND gate letting the MPU "turn on/off" the special solenoid driver inputs), The 7402 (the NOR gate letting the MPU "turn on" the pre-driver transistor, and the driver transistor. Not to mention the physical connection between the Molex header and the pin on the AND gate.

If the coil energizes in test and not with this test you can suspect the 7408.

.

Ok.. I think I re read and understand.. the test I did before on the driver board was with the wire / pin coming from the coil... you want me to find the wire coming from the switch itself to the board ( I wasn't aware it went to the board, no schematic either)

one lug of the switch has a white w/ purple stripe wire.. the other lug has TWO green w/ blue stripe wires..

I'm guessing the two wire lug is the more important and will look for that wire color going to a pin.. then I will ground that pin as you said to test...
 
Question:.. if grounding the coil makes it fire.. why dont they just have the switch go to one lug of the coil and the other to a ground to fire it?

Several reasons. Not the least of which is the fact that there is a ton of current passing there so you would need huge contacts and some means of suppressing the huge spark that would jump between the switch contacts when you opened them.

They also need to let the MPU know that the switch has closed somehow. A pop bumper that uses special solenoid drive circuits will have 2 switches. One in the switch matrix and one going to the driver board special solenoid inputs.

In this case I would suspect that they just ran out of "special" solenoid drive circuits so they had to use an MPU driven circuit.

The reason these "special" drive circuits exist is because the time that the switch is actually closed may not be long enough for the MPU to sense it and drive the solenoid. That's the theory anyway. Bally obviously didn't agree because their pop bumper switches are in the switch matrix and the coils are driven by MPU controlled circuits. There are no "special" solenoids on Bally games.

A better explanation of some of this stuff can be found here:

http://pinball.flippers.info/system6repairpart5.asp

1.2.2 Special Solenoid Drives

All Williams games in the System 3 through 7 era use a set of what are known as "special solenoids". These are solenoids that can be fired either under game control or directly by a playfield switch. The game's program does not run fast enough to detect and fire the coils for the pop bumpers or the kickers. There would be enough of a lag time from the time the ball runs over a pop bumper skirt switch to the time the game fired the bumper's coil that the game would seem extremely "slow".

In order to compensate for this, Williams incorporates six "special" solenoid lines which can be triggered directly from a playfield switch. This circuit bypasses the MPU altogether and fires the coil in real time. For testing and diagnostic purposes, the coil can also be fired by the MPU, and an additional logic IC in the circuit allows the coil to be triggered by both the MPU and playfield switch.

You'll notice that there are two sets of switch contacts on a pop bumper and an additional switch connected to the throw arm on slingshot kickers. These are the "scoring" switches, which are activated when the pop bumper for kicker fires. These are required since the trigger switch is not connected to the MPU.

There were two exceptions to this rule, Time Warp and Stellar Wars each feature 5 pop bumpers. In Stellar Wars, the lower right pop bumper was driven by the MPU and in Time Warp the designers moved the kickers to the MPU controlled solenoid line.
 
Ok.. I think I re read and understand.. the test I did before on the driver board was with the wire / pin coming from the coil... you want me to find the wire coming from the switch itself to the board ( I wasn't aware it went to the board, no schematic either)

one lug of the switch has a white w/ purple stripe wire.. the other lug has TWO green w/ blue stripe wires..

I'm guessing the two wire lug is the more important and will look for that wire color going to a pin.. then I will ground that pin as you said to test...

As I mentioned above that solenoid is NOT driven by a special solenoid drive circuit so those tests are not possible.
 
Note though two games, Time Warp and Stellar Wars, used five pop bumpers and two slingshot kicker. Since there were only six special solenoids, something had to give on these two games. In Stellar Wars, the lower right pop bumper was a CPU controlled solenoid. On Time Warp both slingshot kickers where CPU controlled solenoids.

ah, I just found the same thing you basically did...



And Ed, maybe this being the "odd ball" bumper.. is why there is no cap on it.. The others do have a cap and diode.. this one is a diode only...

for Ed from the repair guide: Also the the special solenoid playfield switch trigger has a 100 ohm 1/2 watt resistor and a 22 mfd 100 volt electroylic capacitor (the positive lead connected to the resistor) in parallel to the switch. This is different than CPU controlled coils that use a switch matrix switch to turn them on (switch matrix switches only have a 1N4004 diode on the switch).


so.. back to figuring out which test is next... for the switch that is..
 
Last edited:
Let me bounce this out loud...

On the switch for the CPU controlled coil thats giving me the problem..
I mentioned there is one lug with a white with purple stripe wire..

The other lug has two blue with green stripe wires.


I traced the white w/ purple wire back to the driver board in the back box.. it goes to a plug in the upper right corner of the board, 2nd connector down.

There are 4 of these white w/ purple wires here.. two to the top pin, two to the 3 rd pin.. the 2nd pin is not used.

Using the continuity tester, I find the 3 pin that has two wires, one of which is my wire to the coil switch.

Both of these , 1st and 3rd pin when I unplug the connector and and test DCV, they both are about 5 DCV.

When I plug the connector back in... I push my tester lead into the connector at pin 1 and still get the 5 DCV..

BUT, when I push the lead into the 3rd pin I only get .6 DCV, the same .6 DCV when I test that same wire right at the switch.. Bad connector in the plug ? or something drawing it down that much when its plugged in?

so.. am I onto something?.. why 5+ dcv on the pin, but only .6 dcv when plugged in..

bad idea to jump the wire to the other pin where it still has 5 dcv ?
 
Several reasons. Not the least of which is the fact that there is a ton of current passing there so you would need huge contacts and some means of suppressing the huge spark that would jump between the switch contacts when you opened them.

They also need to let the MPU know that the switch has closed somehow.

I recently finished up a Data East Robocop where someone had wired all the "special solenoids" (3 pop bumpers and 2 sling-shots) directly to ground. They cut the switches out of circuit and the "return" side of the coils. They jumpered one side of the switch to the return side of the coil....the other side of the switch........soldered straight to the grounding braid. It took me almost an entire day cleaning this mess up....and fixing the massive amount of damage to the driver board.

Edward
 
Back
Top Bottom