Taxi display issues

spoonman

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the display in my Taxi had some issues the jackpot display and the bottom line in the display were dead but the top display worked fine.

I decide to pick up a pinscore display and plug it in and all i get is garbage on the display on all 3 display rows.

I check the sockets and the connectors and no luck. I then retry my old display fog giggles and bam same garbage as the new display (still top display is only one working.

So i am trying to figure out what my problem is as I dont think it is the display anymore.

I am wondering if it is a PIA
[FONT=verdana,arial,helv,helvetica][SIZE=-1]U41: Score display data (1J22), special solenoids B & C.
or
[/SIZE][/FONT][FONT=verdana,arial,helv,helvetica][SIZE=-1]U51: Score display circuit (1J1, 1J2, 1J3).

I was wondering what you guys think and if you agree with my guess where does one buy these PIA chips.
[/SIZE][/FONT]
http://www.youtube.com/watch?v=lKEl5oMehcI
 
Are they 6521 Pia's???

[FONT=verdana,arial,helv,helvetica][SIZE=-1]The Six PIA's and What they Control.
The 6821 PIA chips at U10, U38, U41, U42, U51, U54 can stop a CPU board from booting. Note all six PIA's connect to the CPU reset and IRQ circuits. Here's what each of the six PIA's controls: [/SIZE][/FONT]

  • [FONT=verdana,arial,helv,helvetica][SIZE=-1]
  • U10: Sound output selects, solenoid drives, CPU board flipper relay K1.
  • U38: Switch matrix columns and rows, special solenoids A & D.
  • U41: Score display data (1J22), special solenoids B & C.
  • U42: Sound board (1J21)
  • U51: Score display circuit (1J1, 1J2, 1J3).
  • U54: Lamp matrix columns and rows, special solenoids E & F.[/SIZE][/FONT]
That is a copy paste from the pinrepair website.

I could be 100% wrong and it not be the PIA chips but I am not sure where to track down the issue. I mean it was working not to long ago, i swapped displays and get garbage on screen, tried the old display again and now garbage on that too.

Any ideas where to look? All the connectors look like they are good and secure in the head
 
well i was looking at the cpu and ran this test from pinrepair

[FONT=verdana,arial,helv,helvetica][SIZE=-1]System 11a, 11b, 11c Diagnostic Flashes.
These games do not have a 7 segment display. Instead there is a LED which indicates the memory chip test being preformed. To start the memory chip test, turn the game on or press the bottom CPU diagnostic switch button SW2 on the left side of the CPU board. Quickly count the CPU board LED flashes of the middle (diagnostic) LED, and compare them to the follow chart. [/SIZE][/FONT]



Now this is where i am not sure when to count. I press sw2 and the light goes solid then off then solid. which sounds like it would be 2 flashes but really the diagnostic led comes on when i press the button and i am not sure if i should count that as a flash.


[FONT=verdana,arial,helv,helvetica][SIZE=-1]1[/SIZE][/FONT] [FONT=verdana,arial,helv,helvetica][SIZE=-1]U25 RAM Failure[/SIZE][/FONT] [FONT=verdana,arial,helv,helvetica][SIZE=-1]U25 RAM could not be used. No other tests are performed; the game is locked here until the problem is fixed.[/SIZE][/FONT] [FONT=verdana,arial,helv,helvetica][SIZE=-1]2[/SIZE][/FONT] [FONT=verdana,arial,helv,helvetica][SIZE=-1]Memory Protect Failure[/SIZE][/FONT] [FONT=verdana,arial,helv,helvetica][SIZE=-1]This message means: (A) the coin door may be shut; (B) the Memory Protect switch may be stuck in the ON position; (C) the Memory Protect logic is protecting the audit memory; (D) a U25 RAM failure is occurring. Note this test assumes the coin door is OPEN since this test is initiated ONLY by pressing the CPU diagnostic switch (SW2)[/SIZE][/FONT]

when i open the coindoor and run the test i get no flashes on the diagnostic so maybe looks like it was a 2 flash i was getting which was caused by the door being closed.

looks like i am not getting any further on this.
 
I am still not even sure if it was the PIA's to begin with. Before I hunt down some of these beasts it would be nice to get a nod i am looking in the right direction that these could be the cause.

Looks like if they are I might as well add some sockets too as the PIA's are soldered in
 
I have a bunch of 6520 which are the same thing....

Was that a type-o and did you mean 6521?

A quick google shows me
Comparison of W65C21S to other PIA Devices

The W65C21S is Pin and Functionally Compatible with the following devices.

CMD / GTE – G65SC21
Hitachi – HD6821, HD6321 (CMOS)
MOS Technology – 6521
Motorola / Freescale – M6820, M6821
Rockwell – R6520, R6521, R65C21
ST Micro – EF6821

Would you wanna sell a few and some sockets to jam them in Burt? I suppose even if it is not the fix i need it would not make things worse.

*disclaimer alert* for those who don't recall I am more of a player of pinball vs. a repairer of pinball and am not sure what is causing the garbage on the display and took a guess from reading pinrepair.
 
Okay finally got the display working. I had picked up some PIA's and was going to try and swap them tonight when it occurred to me to try all the combination's of old and new ribbon cables again and it turns out it was a ribbon cable issue.

Anyone who was sitting on the fence wondering if the pinscore displays are nice I can give my 2cents and say they seem to be working out great for me.

Also my lesson learned was not to trouble shoot issues late in the evening on a work night. Seems like I have more success on the weekend after a nap :)
 
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