system 80a display problem

[beaky]

I have a really strange fault on a sys 80a gtb
it will not show the number 1 on any of the 4 players score displays but it will show any other number i.e. it will show 2345670 but it can't display 2145670 or 6543210 but it can display 6543230.

so we get 0000000             2222222 3333333 4444444 5555555 6666666 7777777 8888888 9999999 in test

the credit display will show 00 00 11 11 22 22 33 33 and so on

I haven't looked into it yet but I have a hunch at what it could be.

has any one ever come across this one?    

[Marty Machine]

That's a nasty one, considering the segments for a "1" are also used in 7, 8, 0 etc, so it disproves any theories about missing bits, wiring etc etc....

[Homepin]

It's a Gottlieb - anything's possible.......

[beaky]

yep it's weird

the even weirder thing is at first it was only 3rd and 4th player doing it, the only reason i noticed it is because the 1 was missing off the high score on the bottom displays.

then after swapping 1st with 3rd and back again all or them did it.   

[Marty Machine]

So, have you put a known working display in the machine to see if it faults too??

Is it something really bizarre like the displays are so aged and the current drawn for a "1" doesn't fire up the segment current correctly? therefore everytime a "1" is displayed it simply blanks out.
Assuming the high-voltage on the displays is also within spec too??

weird weird weird....

[MartyJ]

I would be testing each display individually with others unplugged

[The pinballist formally known as Dean Morgan]

I would be testing each display individually with others unplugged

I will check schematics tomorrow as I can't remember what drives the 1 segment. On system 1 games the use two separate chips, ls21 from memory, to drive the 1 segments, can't remember if system 80 is the same, so I wil check tomorrow.  Also I have seen crook 5101 ram cause display issues.

[beaky]

yep, I have checked with only 1 display connected and known working displays

[4_amusement_only]

Which game is it for?

[beaky]

super orbit

[Strangeways]

I would be testing each display individually with others unplugged

I will check schematics tomorrow as I can't remember what drives the 1 segment. On system 1 games the use two separate chips, ls21 from memory, to drive the 1 segments, can't remember if system 80 is the same, so I wil check tomorrow.  Also I have seen crook 5101 ram cause display issues.

I won't be surprised if it a bad 5101 - but it is easy to rule out. Run the full tests, and you would see the 5101 Error. Also check the ROM test. Unfortunately I don't have a sys80a schematic to follow, but it sounds like a board problem rather than display. Would be great if you could isolate the CPU / Display if you have another handy.

[The pinballist formally known as Dean Morgan]

Ok looking at the schematics, 1 on each of the displays is segment 'h'. This is a different segment then all other numbers. Segment 'h' on player 1 to 4 is driven by gates on Z16' pins 10 and 12.  I would be fairly certain this is your fault, replace Z16 it is a 7404.

The reason the 1 works on the credit display is that segment 'h' on this display is driven by Z17.

This should fix it. If not it may be U5 the 40 pin 6532 display control, but I doubt it. Replace Z16 and report back.

You could also check pins 8 and 16 of A1 J2 but I doubt they would both be faulty. Pin 8 drives seg h for 1st and 2nd player and 16 for 3rd and 4th

[beaky]

Ok looking at the schematics, 1 on each of the displays is segment 'h'. This is a different segment then all other numbers. Segment 'h' on player 1 to 4 is driven by gates on Z16' pins 10 and 12.  I would be fairly certain this is your fault, replace Z16 it is a 7404.

The reason the 1 works on the credit display is that segment 'h' on this display is driven by Z17.

This should fix it. If not it may be U5 the 40 pin 6532 display control, but I doubt it. Replace Z16 and report back.

You could also check pins 8 and 16 of A1 J2 but I doubt they would both be faulty. Pin 8 drives seg h for 1st and 2nd player and 16 for 3rd and 4th

will do
Still haven't got to this board yet but will get back to it by thursday.
thanks.

[The pinballist formally known as Dean Morgan]

How did you go?

[The pinballist formally known as Dean Morgan]

That's a nasty one, considering the segments for a "1" are also used in 7, 8, 0 etc, so it disproves any theories about missing bits, wiring etc etc....

Marty, different on these Gottlieb dispays, segment 'h' is only used for 1.  Not used in any other number