System 11 B Display Problems - send help!

Hi everyone working on getting a dead as a door nail police force back up and running - it had some battery damage and wasn't booting, I resolved that issue with replacing a few IC chips and cleaning up the damage.

The displays were not working at all which I traced back to the -100V circuit where there was a bad resister (R4 I think it was) Anyway now I got the voltage correct, this is what I get (top main display works almost perfect) bottom main display has middle segments and left bottom and bottom out, and the small jackpot display at the top does not work at all. My question before I start testing every chip etc on the display board is could this be something with the CPU board since thats where my other problems started and if so where should I start investigating?

IMG_3581 (resized).jpg

#2 7 years ago

DEC

GRUMPY

Pinside member

OP
Quoted from fusion301:
could this be something with the CPU board

Yes.

OP
Quoted from fusion301:where should I start

Buy a logic probe. Check the SRC packs for low pulses for the missing segments.

#3 7 years ago

KEN

fusion301

Inactive member

Thanks Logic Probe added to my amazon cart

#4 7 years ago

DEC

GRUMPY

Pinside member

Let me know when you get it and start troubleshooting.

#5 6 years ago

KEN

fusion301

Inactive member

Got the logic probe, started messing around with the little knowledge I have - haven't found anything too obvious on the CPU board. Can you point me in a direction - keep in mind this is my first time trouble shooting with a logic probe.

#6 6 years ago

DEC

GRUMPY

Pinside member

OP
Quoted from fusion301:
Can you point me in a direction - keep in mind this is my first time trouble shooting with a logic probe.

Logic probes make troubleshooting real easy. In your pic the bottom display looks like its missing segment C and D. So lets start with segment D. On page 88 of the manual it shows the display board component layout. So start at display 2 D segment, it goes thru U-19 and then thru U-11 and then to J-5 pin 5. This is a blue/green wire and goes the CPU J-3 pin 5. Put your game in display test and lock it on a number that uses the D segment on the bottom display like 2,3,5,6 or 8. Now check for low pulses at J-3 pin 5. If you have low pulses at the cpu then your problem is on the display board.

#7 6 years ago

KEN

fusion301

Inactive member

OK, so I locked the number onto number 8 so both C and D should be on - tested J-3 pin 5 and 7 (segments that are out) on the CPU board and my probe just goes to HI, the other pins are all pulsing on that connector. Im starting to think there is something wrong with U51 on the CPU board, I have already changed U41 and U42 (am I on the right track here?)

BTW Thanks so much for taking the time to help - hopefully this also helps other people with similar display/battery damage issues

#8 6 years ago

DEC

GRUMPY

Pinside member

OP
Quoted from fusion301:
Im starting to think there is something wrong with U51 on the CPU board

If they were stuck low, then it would be pull up resistors. Since they are stuck high, this is a Pia chip (U-51) or a broken traces on the board from the corrosion. I would retest, but this time check for low pulses on the pins of the Pia chip. This will tell you what you have left to do.

#9 6 years ago

KEN

fusion301

Inactive member

Great information, thanks I will replace that chip after testing again and let you know the outcome.

#10 6 years ago

KEN

fusion301

Inactive member

Ok so I replaced U51 we have some progress! - Still remaining out are all the interior letters of the digit h,j,k,r,p,n of Display 2

IMG_3584 (resized).JPG

#11 6 years ago

KEN

fusion301

Inactive member

So if Im looking at this correctly it looks like they go to connector J3 to IJ22 pins: 10 (dot') -- 9 (r') -- 8(p') -- 7(n') -- 6(m') -- 5(k') -- 4(j') -- 3(h') Which all look like the are controlled by PIA U42.

Going to test these pins at IJ22 and see what we get with all digit segments on.

#12 6 years ago

KEN

fusion301

Inactive member

So here's a dumb question - does the bottom display even use the interior segments in the software or test mode - through all the menus and when I start a game I haven't seen where it uses any of those special characters.

#13 6 years ago

RDM

boscokid

Pinside member

OP
Quoted from fusion301:
So here's a dumb question - does the bottom display even use the interior segments in the software or test mode - through all the menus and when I start a game I haven't seen where it uses any of those special characters.

Nope, not used. Looks like you have fixed it!

#14 6 years ago

KEN

fusion301

Inactive member

Great.. Big thanks to GRUMPY for taking the time to teach me how to use the logic probe and trouble shoot these displays. This was all a direct result of battery damage on the CPU so if you have display issues and battery damage, this could be your problem.

The Jackpot display was just broken, I replaced it with another 7 digit display and everything is working.

#15 6 years ago

DEC

GRUMPY

Pinside member

OP
Quoted from fusion301:
Ok so I replaced U51 we have some progress!

Looks like its time for some pinball!!!
Enjoy your hard work.

3 weeks later

#16 6 years ago

RDM

boscokid

Pinside member

GRUMPY i am posting a followup question here since it's related to fusion301 issue.

My Police Force has now lost the d segment on the bottom display. I used a logic probe to verify pulsing at J-3 pin 5 so my problem is on the display board. I checked the output of pins 6 (d),4 (c),15 (b) and 2(a) on U11 and they are all pulsing so next up is U19 however it's -100vdc so logic probe isnt going to work here?

Looks like the only things left are U19, R59 (which reads 8.34k ) and the actual display glass. There is no damage to the traces on the display board.

I have seen the 'd' segment flicker on a couple times while testing but seemingly at random and not for long. I have had this game a couple years and this is the first I have seen this issue

The bottom display is original. TNT replaced the upper display in 2000 based on the sticker

#17 6 years ago

DEC

GRUMPY

Pinside member

Quoted from boscokid:
so next up is U19 however it's -100vdc so logic probe isnt going to work here?

You can check pin 2 of U-19 with your logic probe just to make sure it has pulses, if no pulses a bad trace or cold solder joint. If you have pulses there and your display is crisp and bright I would change U-19. You can also lock display on number 8 and use your DMM set on 200 volts DC and check pin 18 on display 1 then compare it to display 2. If they are the same then its a display problem, but remember there is a lot a fluctuations when checking voltage on displays because they are strobed on and off. Hope that helps.

#18 6 years ago

RDM

boscokid

Pinside member

I get pulses at U19 pin 2. Display is crisp and bright.

This may be a dumb question but how do I determine pin numbers on the glass? Didn't see any clues in the manual or on the board, is pin 18 just the 18th from the left? If that's the case it looks like I am getting 4.87v on both display 1 & 2

display (resized).jpg

#19 6 years ago

DEC

GRUMPY

Pinside member

Pin #1 is on the shooter lane side. I think you are on pin #72.

#20 6 years ago

RDM

boscokid

Pinside member

The 18th pin from the right on the bottom display is -9.8v
The 18th pin from the right on the top display is -64.4v

So that confirms your theory that U19 needs to be replaced?

#21 6 years ago

DEC

GRUMPY

Pinside member

Quoted from boscokid:
So that confirms your theory that U19 needs to be replaced?

Yes sir. U-19 is a pain to get at so take your time.

1 week later

#22 6 years ago

RDM

boscokid

Pinside member

Well I replaced U19 and 'd' segment still not lit on the bottom display.
Went back and verified pulses at U19 pin 2
Went back and checked voltages at pin 18 on upper and lower and got -5.4 on the lower and -65 on the upper
I measured the resister on the bottom display R59 and get 8.43
I measured the resister on the top display R42 ( i think) and get 8.10
verified continuity between U19 pin 2 and bottom display pin 18 with a meter - they also visually look ok

so now what? The U19 was date correct 9103 and manufactured in Philippines

I swapped my Jokerz! display into Police Force and the bottom display worked fine so the problem is still on the display board

when swapping the police force display to jokerz the bottom 'd' segment is still out

#23 6 years ago

DEC

GRUMPY

Pinside member

Well I think that it's not your lucky day. Your display segment must be shorted out and pulling the signal down. Now your left with replacing the display. Is it worth your time and money? A new display is over 100.00 + shipping.

#24 6 years ago

RDM

boscokid

Pinside member

Thanks for a the help. Doubt its worth seeking out a new display glass at that price, so I will look at my other options.

#25 6 years ago

DEC

GRUMPY

Pinside member