(Topic ID: 207613)

System 80b alphanumeric display missing digits


By bmsx

2 years ago



Topic Stats

  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 2 years ago by cfh
  • No one calls this topic a favorite

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#1 2 years ago

Hi,
I have an issue with Gottlieb sys80b alphanumeric display. It have empty spots like on photo (auto test):
tqZv7XB (resized).jpg

Data is correct. Some of digits are darker.
It's glass broken or swapping chips will help? If it's chip problem, which one? U1-U5

jQdg2Ry (resized).jpg

No visual damage found. Connectors are clean. Ground mod done.

#2 2 years ago

It seems you are missing the first 5 digits (not segments) at the upper display, and the 3rd at the lower. Hard to say what is the cause without measuring. I would take my oscilloscope and measure if the buffers U4 and U5 are working. Without it a wild guess: U1 is defective and jamming U2?? You can try to remove U1 and see if the 3rd digit at the lower display appears again. Exchange U1 and U2 with eachother and see if the problem moves? Maybe someone has a better idea?

#3 2 years ago

Thank you for reply. Of course it's digits problem. My language mistake.

3 weeks later
#4 2 years ago

Thank you for advice. I changed U1 with U2 and I think this is it! Problem moved to lower display. I ordered new chips. When they arrive I'll confirm repair.

WP_20180213_18_00_18_Pro (resized).jpg

1 month later
#5 2 years ago

Repair confirmed =]

WP_20180327_19_48_51_Pro (resized).jpg

#6 2 years ago

There's an easier way to test this...

When you figure out which digit you're missing (display test), look at the schematics. It will show which "D" pin on U1 or U2 controls that digit. Put the game into display test, then just jump the missing "D" pin to the pin next to it on the Ux chip. This way you can test the theory that the Ux chip is bad, without having to remove/desolder anything.

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