(Topic ID: 152961)

Police Force Display Segments Always Lit


By scupbucket

4 years ago



Topic Stats

  • 10 posts
  • 3 Pinsiders participating
  • Latest reply 4 years ago by GRUMPY
  • Topic is favorited by 1 Pinsider

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#1 4 years ago

Hi Guys! Currently 90% done with my PF project and was wondering if anyone could offer some info on a display problem I’m having with the player 3 area. Seems segments g and m (think those are the right ones) are constantly lit and flashing/moving in sync with the jackpot display. Tried doing some simple things suggested in other posts like reseating and swapping the ribbon cable but no luck. Time to dive a bit deeper. I can't post my video link yet (forum rules) but attached are a few screencaps. Great site and any help with where to start would be appreciated!

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1 week later
#2 4 years ago

Buuump! Ok, I can finally post some video...

You can see the player 3 area g' and m' segments on display 2 flashing and moving in sync with the jackpot display. I pulled my hair out learning to read the schematic but I think I might have an idea of where to start poking around. I tracked the g' segment from U19 on the display board to SRC9 then to U51 on the CPU and the m' segment from U20 on the display board to SRC4 then to U42 on the CPU. Not sure where to go from here. Interesting to note that according to the schematic, the two problem segments are connected just under display 2 at W1? Not sure what that component is... resistor? Any PF or Taxi guys have this problem? I feel so new...

TIA!

#3 4 years ago

Do you have a logic probe? You need to look for low pulses at the SCR pins for segment g and m.

#4 4 years ago

ah-ha! I don't but know someone that does... might have to put him to work on it... I have no idea how to use one. So are the SCR resistor packs more prone to failure rather than the actual U41 and U51 chips? It it old components or something else that commonly causes them to fail?

#5 4 years ago

I'd start by looking for battery damage on the CPU board. That commonly causes problems like this. Get a flashlight and look closely at the resistor packs and around the battery holder. Any noticeable corrosion? Post some pics?

#6 4 years ago
Quoted from scupbucket:

So are the SCR resistor packs more prone to failure rather than the actual U41 and U51 chips

I have seen both fail.

Quoted from scupbucket:It it old components or something else that commonly causes them to fail?

27 years old takes its toll, but John is correct that a lot of damage starts from the batteries.

1 week later
#7 4 years ago

Ok... I bought a logic probe. Looks like there was definitely some minor acid damage in the past due to a few jumper wires in place and a brand spanking new battery holder. I'll get some pics shortly. Another problem that popped up was the flippers would occasionally stop completely so I tracked the problem down to the K1 relay. Replaced that and the flippers work just fine now at all times.

As for the display, I have the probe hooked up but not really sure where to go from here. I'm in display diagnostics mode and tracked down the g' and m' segments to SRC9 pin 8 and SRC4 pin 5. According to the probe, both are reading low with a rapid pulse (beeper) and responds accordingly when stepped through the different numbers. When those segments are not lit, the reading is high. When lit they read low. Cool! Not sure what i did though...

#8 4 years ago

Do the segments go out with the ribbon cable disconnected?

#9 4 years ago

They do... I tried a few other tests after reading up a lot on other similar problems. Determined to learn how these tick and what to look for in the future, especially after selling my Indiana Jones 10 years ago when I though it was "broken" (dumb dumb dumb). Read a lot of your troubleshooting and guidance... a TON of great info so thank you.

All suspect SRCs tested low pulses. I checked resistance on them and all were good within the 4.7k ohm spec except SRC4 which tested at 2.5k ohm across the pack. Not sure how that will affect the display but most likely will need some attention in the future. I went to test the 7180s on the display so I loosely connected all cables to the display board, booted the game up, and noticed the trouble segments were off and everything was working 100%. So turns out I overthought it all and it ended up being a loose connection somewhere along the display board. Still never hurts to learn how to troubleshoot I guess....

One thing that was a bit confusing along the way was the absence of the referred schematic for the jackpot display. The manual says to "refer to assembly drawing D-12159" but I can't find it anywhere. It looks like this drawing would make sense of how the main displays control the jackpot display.

Thanks guys!

#10 4 years ago
Quoted from scupbucket:

except SRC4 which tested at 2.5k ohm across the pack.

I have seen this before and when the pack is removed it reads correct. Something else in the circuit changing the resistance.

Quoted from scupbucket:Still never hurts to learn how to troubleshoot I guess....

Sounds like you have a good grasp on how this stuff works now, so the next problem you encounter will seem simple.

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