(Topic ID: 281867)

Stern "PINBALL" odd switch behavior issues

By wawhite92025

3 years ago


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left drops b.jpg
Pinbal_SwitchMatrix_Playfield(1).gif
3 Alltek boards in Stern PINBALL backbox.png

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#2 3 years ago
Quoted from wawhite92025:

Does anyone have any experience with a problem like this in an early Stern or Bally solid state and what is the cure?

The cause is a shorted diode/switch somewhere, the cure is finding and fixing it

Put the game in switch test. Does it report "0" in the Ball in Play display?
Then remove the J3 connector (cabinet switch harness) off the MPU board and check your drop target switches again - do you still get incorrect switches being reported?

You mention the top saucer sometimes not responding - have you determined if this is switch or coil related? Is the switch gapped properly?

You might find this recent switch matrix problem thread useful reading:
https://pinside.com/pinball/forum/topic/eight-ball-deluxe-3rd-player-jumps-to-4th-player-while-ball-in-play

#6 3 years ago
Quoted from wawhite92025:

The top saucer problem is a mystery because with the ball sitting in the saucer if I restart the game the saucer/kick out works immediately without any change to the switch, but I'll study it again.

The game will always activate the saucer coils after power-up irrespective if there's balls sitting in them or not.
The fact this is happening is telling you the coil is working and it's a switch related problem.

Next time the ball gets stuck in the top saucer, go immediately to switch test mode and see if the game is recognising that saucer switch as being closed.

#9 3 years ago
Quoted from wawhite92025:

I removed the J3 connector when in switch test mode and the switch errors are the same

Ok, so it's not a cabinet/front door switch causing an issue within the switch matrix.

Quoted from wawhite92025:

Any idea what is the reason the left outlane switch fires the left pop bumper and shuts of the power to the MPU, and why the right outlane lights the tilt light, fires the right bumper, but does not turn off the game?

If you look at the switch matrix diagram below, the left outlane, left pop bumper and slam switches are all on the same "I7" row switch return line. A short somewhere in your switch matrix is causing a switch on that line to shadow across other switches. Ditto the right outlane, right pop bumper and tilt on the "I6" row switch return line.

If you can, perform this procedure I mentioned in the thread above and let me know the results:
https://pinside.com/pinball/forum/topic/eight-ball-deluxe-3rd-player-jumps-to-4th-player-while-ball-in-play#post-5954054

Pinbal_SwitchMatrix_Playfield(1).gifPinbal_SwitchMatrix_Playfield(1).gif

#11 3 years ago
Quoted from wawhite92025:

Is this the procedure you refer to?:

Yes, that's the procedure. Which part(s) don't you understand? (so I can make it more clear)

Can you post some pictures showing the wire connections on all the drop targets and the outlane switches?
Oh please post a clear picture of the J2 connector on the MPU board so I can see each of the wire colors and where they're positioned.

Can you lastly clarify if switch test mode reports "0" in the Ball in Play display when no switches are closed (i.e. all drop targets are raised and the ball removed from the machine)?

#16 3 years ago
Quoted from wawhite92025:

Connectors photos linked.

Cheers, nothing stands out on a first look.

Quoted from wawhite92025:

I know that some of these colors do not match the schematic/matrix.

Use the playfield schematic I posted above, it has the correct wire colors listed.

Quoted from wawhite92025:

What I don't understand is how the MPU can show switch numbers 1, 3, 5 for three of the drop targets when there are no such switch numbers?

The switch test mode on these early Stern/Bally games is flawed, it only displays the lowest number closed switch. i.e. when you press that left outlane switch, because of your particular fault you're not seeing the game telling you that it's also seeing switches #40, #32, #24, #16 as well as #8 being closed. So when you press that left outlane switch all these other switches I just mentioned are being seen as closed aswell. This is a phantom effect with your fault and how switch matrix's work. This is the reason I asked if you could run the switch test mode and press the switches in reverse order of the switch ID numbers listed in the manual.

The switch matrix is made up of columns and rows. Referencing the matrix picture above, when the game wants to read the switches, it first raises strobe #4 line from zero to 5 volts. It then reads all the eight switch return lines at the same time. Any of the switches on those return lines that are closed with respect to strobe #4 will report 5 volts, open switches will report zero volts.
Strobe #4 is then released back to zero volts and then strobe #3 is raised from zero to 5 volts. Again all the eight return lines are read at the same time. Any of the switches on those return lines that are closed with respect to strobe #3 will report 5 volts, open switches will report zero volts.
Ditto strobe #2, #1 and then #0.
The diodes on all switches is what separates the return line signals from the strobe lines to prevent phantom reads.

Now in your scenario, all the wrong switch readings you're getting are coming from the strobe #3 line (white-yellow wire).
The errors you're getting suggest the strobe #3 is shorted to something. The moment you close a switch on strobe #3 the switch return line is getting stuck such that it's reported as closed on every strobe line read.
But this doesn't explain why two switches on that strobe #3 line are apparently ok (drop targets B and D). Can you confirm this?

BTW, when you're pressing switches with your hand, make sure no other part of you body is touching ground.

Can you comment on the below:

left drops b.jpgleft drops b.jpg

#19 3 years ago
Quoted from wawhite92025:

Where did you find a correct matrix or did you create it yourself?

Glad you got it going!

The switch matrix diagram in the online "Pinball" schematics is too blurry to use so I borrowed the playfield schematics from Sterns next game called Stingray. It actually runs the exact same software and is just a playfield re-arrangement. It was a cheap way for Stern to produce new games without having to write new code for each game - they did this with some other early games too.
I had to make some modifications to the switch names in that diagram as you might have noticed but the wire colors matched what you listed is in your game.

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