Aspen Hill, MD
1980 Stern Galaxy. The lower right pop bumper keeps firing while the spinner keeps spinning. All and any help would be appreciated.
(Topic ID: 174394)
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Galaxy
Stern Electronics, 1980
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Do you have the schematics?
Looks like those two switches are very close on the playfield. Have you opened it and looked for shorts?
I do not have the schematic but I will be downloading it soon. The two switches are not close together. I did look into the machine. I have another galaxy and it looks like they have two different style switches on either machine. I am a novice and new to pinball so any explanation in layman's terms would be awesome.
With your machine unplugged, raise the playfield and look at the wires that go to the two areas I've circled in red. If you have a multi-meter, use that to check for continuity between those two switches. You should not find any. If you have continuity there is a short and that's why your pop bumper fires when the spinner activates.
If the number 3 I've circled isn't what's firing with the spinner, look and test for shorts between the spinner and the misbehaving item. Right slingshot maybe, located at P7?
Okay I got the wiring diagram. It says that the spinner Target shares a white / green wire with the lower-right pop bumper And the left turn lane and stand up Target. First I checked the wires going to the switch on the spinner and they are correct then I checked the diode on the switch for the spinner and that is in order. Then I went over to the pop bumper checked it and the diode on the switch for it and it all checks out. I know you said that there should not be continuity between the spinner and the pop bumper but they do share the white/green wire. I just checked the diode on the center yellow drop target. Just scratching my head over here. I forgot to mention that this machine is new to me I have not gotten used to the gameplay. I did notice that sometimes the pop bumper fires with the spinner and sometimes it does not. Could it be the sdu board?
If they share a wire it's probably a switch matrix problem. I didn't see a diagram for the matrix in the manual but I might have missed it.
Have a look at the pinwiki on switch matrix issues.
http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Switch_Matrix
You'll want to figure out which row or column the two switches share and start your troubleshooting there.
Okay gentlemen thank you for all of your support. I tried putting paper on the switch for the spinner and the paper blocks. it does not work. I gaped the switch and still has the same issue. I play the game with the glass off and kept spinning the spinner while hitting different things on the Playfield and found out that the pop bumper acts up only when you hit the yellow drop Target on the left I am going to check the diode on the switch before anything else. I have found a few other inconsistencies but I will get to that later. Please let me know if I should be checking for anything else besides the diodes.
Okay guys I checked the diode on the yellow drop Target on the left and the diode is fine. I also switched out the switch on the spinning Target and I have the same results of the pop bumper firing when the spinner spins while the yellow drop Target is down. Any clues anyone?
I think what Homepin was suggesting was put some paper between the pop bumper switch. If the pop bumper still fires with paper between the switch contacts we'll know it's an electrical problem somewhere and not just a sensitive pop bumper.
Go into the self test #5 (switch test). With ball(s) removed from the game does the test show any switches closed? With the target up, activate the spinner. Does the test show any switches closed now? More than one? (edit: 
Troubleshooting might be tough. Pinwiki says "NOTE: Multiple closed switches will NOT display anything other than the lowest numbered switch. This can be an issue with various switch matrix diode problems, as the switch displayed as closed may not be the switch with a problem. There is a special test rom available that will show ALL closed switches in a sequence similar to how Williams' machines did so")
Now drop the target and note any switches shown as closed. Activate spinner with target down. Same switches or different than with target up?
Pinwiki shows this for the switch matrix. If I'm reading it correctly #5 is the spin target, 13 is the lower right pop bumper, and 10 is the yellow drop target. 5 & 13 are in the same row on the switch matrix, 10 & 13 are in the same column. Not sure what that means but I'll keep digging. Here is some good reading: http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Switch_problems
SternGalaxySwitchTest (resized).jpg
SternGalaxySwitchMatrix (resized).jpg
Also check out this thread about another Stern Galaxy with a switch matrix problem. The same troubleshooting methods will work for you.
https://pinside.com/pinball/forum/topic/stern-galaxy-strange-intermittent-kicker-issue
I think this project might be a little bit out of my Realm. I did put a piece of paper between the contacts of the switch for the lower right pop bumper with the yellow drop Target down spinning the spinner and it did fire even with the paper in between the switch. I might need someone local to take a look. I will try the switch test before finding someone. The sad part is that I already replaced mpu, rectifier and put LEDs. It looks awesome though.
Hang in there 
Can you tell us if this problem occurs when all drop targets are reset in the up position or only when some drop targets are knocked down (and which ones)? It will help to build a picture of what's going on.
Let us know the result of the switch test when you've done it.
Thank you ,Yeoldpinplayer, for all of the info. I will read up later tonight when I get home.
"Quench" The problem occurs when the yellow drop target is knocked down only and the spinner is hit. It makes only the lower right pop bumper fire. When the yellow target is reset in the up position, it does not make the lower right pop bumper fire.
I do have a new symptom. When the yellow and red drop target are down, the top pop bumper goes dead.
Just to recap:
Yellow drop target down + spinner = lower right pop bumper fires.
Yellow + red drop target down = dead top pop bumper
Was this machine working before or have you just bought it with this problem (just wondering if it's a new issue or pre-existing)?
Looking at the switch matrix schematic, your symptoms are pointing to a stuck coin chute 2 switch (switch for the center coin slot) and if it has a diode (there may or may not be a diode there), the diode is probably shorted.
So can you have a look at this switch and see if the wire actuator is in the down position - compare it to the other coin chute switches for reference. If there is a diode on this switch, can you check it?
The switch test in service mode will tell you straight away if this switch is stuck, so recommend you run it. Just press the test switch inside the coin door 5 times to get to the switch test.
"Happy Days Everyone"
I would like to thank all the members here at pinside for helping me track down this gremlin. The problem was the brown/white wire on the center coin chute. It was on the wrong lug. I purchased the machine non working and replaced the MPU with an Altec and replaced the rectifier board since it was very toasty . Everything on the playfield works as it should thanks to you all. I owe you guys a beer if ever in Maryland.
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