(Topic ID: 232752)

Alien Star: half of my switches are out, System 80A

By ryanwanger

5 years ago



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#1 5 years ago

The switches on rows 5 and 6 are completely dead on my Alien Star.

- All wires on A1-J6 have continuity to the appropriate traces on the board.
- The ground mod has been done between A3-J1 and A1-J4.
- I've checked the switches under the playfield that correlate to both of the rows, and all wires are connected and secure.
- I've checked the continuity between the wires and the traces on the 1A7-J1 board near the tilt bob, and it's all good.

This my first System 80. Where do I go from here?

#2 5 years ago

Unplug all the connectors in the back box and reconnect them. System 80 game issues are almost always connector related.

#3 5 years ago

Do you have a probe?

Is that pins 15 and 16 or 16 and 17? Not sure if you're counting rows from 0...

Pins 14-17 (R4-7) all go through Z14. Is that what you checked continuity to?

It's possible those two inputs on Z14 are bad, but usually the other two would be bad too...

One other thing to try is to set all your dip switches to 'off'. They are connected into the same switch matrix row inputs as the playfield, so if that effects things it will narrow down the issue.

#4 5 years ago

@donjagra I reseated all the connectors in the backbox and under the playfield. Same issue.

@zacaj I do not have a probe. I guess it's a little confusing because the switch matrix seems to label the connector starting at 1, but the rows and columns starting at 0. Pic attached. It's switches 40-45 and 50-55 that are out (I hadn't tested 57, the tilt bob).

Screen Shot 2018-12-30 at 1.40.18 AM.pngScreen Shot 2018-12-30 at 1.40.18 AM.png

When I said I checked continuity on that connector, I was testing that each wire had continuity with both the connector, and the appropriate trace on the board. I did this for all wires going into that connector (A1-J6), which has around 17 or 18 slots, though not all are used.

Switching all the dip switches off does nothing, unfortunately.

#5 5 years ago

If you can totally rule out connectors, then you have to circle back to ic problems on the mpu board. I haven't had much luck replacing ic chips on the original boards, fortunatly the rottendog boards are cheap. If you can do the work yourself that's awesome, but if you have to pay someone, you should probably just upgrade.

https://www.thepinballwizard.net/rottendog-circuit-boards/gottlieb-system-80/80a-mpu-board-mpu080/

#6 5 years ago

Ah, okay. I was interpreting 'R0' to be row 0, but on a gottlieb the Rs are columns

So this is A1J6 pins 5 and 6 that are having an issue.

All the rows go through the same two chips so not much reasoning that can be done without a probe. I'd just start by replacing Z11.

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#7 5 years ago

Cool. I'll give that a try by testing Z11 using this method: http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit

I've done boardwork before, but I'm also not opposed to replacing the entire board. Wouldn't want to get a new board unless I was relatively certain that would fix the issue.

#8 5 years ago

Make sure the main connector between the mpu and driver has been checked. Everyone complains about the grounding on these games, but it is only because the grounding goes through the connectors instead of a braid, and the connectors are crap. There might be a connector under the playfield for those rows too, so check everything.

8 months later
#9 4 years ago

Finally got around to fixing this. It was indeed the Z11. Huge shoutout to @zacaj!

Replaced it with this from Great Plains Electronics: https://www.greatplainselectronics.com/proddetail.asp?prod=7404

For good measure, I socketed it with this socket: https://www.greatplainselectronics.com/proddetail.asp?prod=IS-314-MP

Alien Star lives!!

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