Author Topic: DE Display problem - ALL ON ?  (Read 1266 times)

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Marty Machine

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Re: DE Display problem - ALL ON ?
« on: December 28, 2008, 06:35:03 PM »
Hi All,

Out of sheer boredom today i decided to look deeper into my display problem.

Looking at the schematic pointed me to a 6821 (PIA) chip that controls the data & strobes to the score display PCB.
The 6821 was in a socket, and the other 6821's on the main board were not, immediately i was suspect of the socketed PIA.
I replaced the 6821 today, and after powering up the pin, i can now see Alpha-numeric words & scoring.
I've played thru many games and everything displays as expected.....so far so good.

However, that's only the 'top' 2 displays (being the 2 Alpha-numeric ones) that work nicely.
The 2 displays under them (7-seg) are still just OFF, nothing at all, ever!

I'll spend more time next week on this, as i need to dig out my logic probe and/or Cro to trace the missing signals that drive the 7-seg displays.
I'm guessing (at this stage) that a buffer chip on the display PCB has paffed out, soon to be confirmed!  &&

I play the machine too much to be bothered getting Techy with it, at the moment  %.%

Getting there ...  #*# :lol
MM.