(Topic ID: 248281)
Omaha, NE
Connector at the CPU board - probably a bad (worn out or contaminated) contact at the "a" segment.
The "a" segment is at CPU connector J2 pin 13. If not bad contact, follow wire to displays and look for break.
This segment is driven by Z17, Hopefully not a bad Z17 as it is obsolete but not impossible to find.
But since characters are correct (other than the "a" segment) then the spider IC at CPU board U6 is OK (whew!).
If wiring looks good: With the machine turned OFF(!) -- pull plug from J2 and reinstall. If symptoms change then the connector needs to be repinned.
With these Gottliebs - always suspect connectors first.
The first step I would take is clean off the metal finger contacts on the PCB with a pink rubber eraser. They tend to have a build-up of tarnish and grime. Half the time, that prevents a good connection.
I have pulled J2 off several times and reseated it but that didn't change anything. I can replace that connector at pin 13, but do you count from the top down or bottom up?
Quoted from ita47:I have pulled J2 off several times and reseated it but that didn't change anything. I can replace that connector at pin 13, but do you count from the top down or bottom up?
There are small numbers near the first and last pins on the PCB
1 week later
Thanks again guys for the help. I’ve done more checking and I believe my Z17 chip is bad. I have continuity from leg 13 on the chip Z17 all the way to the displays so it isn’t a bad connection. Then I got my brothers logic probe and leg 13 reads low, no pulsing like the other legs. I found some new old stock chips on eBay and ordered them. I should have them Monday. Hopefully that will fix my display issue.
I finally got my replacement chips for Z17 today. I installed it tonight and my player 3 & 4 now have the top (a) segments, so it was a bad chip after all. It was tough to get the old chip out, but I finally succeeded. I installed a socket so if it ever happens to fail again it will be an easy swap. Thanks again to G.P.E. And Force Flow for you help. I am thrilled to get this fixed.
A739BBC6-96AE-44B8-840C-9BB69840DF76 (resized).jpegQuoted from RWH:So it seems system1 displays and the chip that drives them are the same as the ones for system80, is that correct? I thought the system80's were built differently but it appears to be not so.
I couldn't tell you because I don't have any system80 games. Maybe someone with more Gottlieb experience can chime in and answer your question.
Quoted from RWH:So it seems system1 displays and the chip that drives them are the same as the ones for system80, is that correct? I thought the system80's were built differently but it appears to be not so.
Yes -- same display decoder. 7448 or 74LS48.
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