(Topic ID: 281793)

Williams System 6A - Fix score displays doing the "wave"? (video)

By Kisco

3 years ago



Topic Stats

  • 5 posts
  • 3 Pinsiders participating
  • Latest reply 3 years ago by Tuukka
  • No one calls this topic a favorite

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#1 3 years ago

Please first watch the video on the issue (4 seconds): https://i.imgur.com/VaDGUax.mp4

The video is what it looks like from the eye as well, not the camera shutter. I am here to ask where to start as this is something out of my area to diagnose, but I should have the capabilities to fix it. Below are some high-resolution photos of the boards incase they are needed. Thanks in advance.
boards.pngboards.pngdisplay board.pngdisplay board.png

#2 3 years ago

The 'refresh rate' of the displays is driven by the IRQ line (TP5 on the MPU). This should be around 1kHz (30us low and 70us high). If it isn't getting generated correctly, you can see the digits refresh individually like that.
First step would be to check TP5 with a scope or logic probe. If you're not seeing a 1kHz signal, then trace back to the components involved in generating it... Any corrosion around IC5, IC11, or IC25?

#3 3 years ago

Replace the electrolytic caps at top left corner of power supply board.

#4 3 years ago
Quoted from yendor0:

The 'refresh rate' of the displays is driven by the IRQ line (TP5 on the MPU). This should be around 1kHz (30us low and 70us high). If it isn't getting generated correctly, you can see the digits refresh individually like that.
First step would be to check TP5 with a scope or logic probe. If you're not seeing a 1kHz signal, then trace back to the components involved in generating it... Any corrosion around IC5, IC11, or IC25?

I do not own a scope so sorry if that doesn't help, I do own a multimeter if you have any other tests...
I took some photos of IC5, IC11, and IC25 for you to inspect as I am not exactly sure what to look for.
IC5.jpgIC5.jpgIC11-IC25.jpgIC11-IC25.jpg

Quoted from Tuukka:

Replace the electrolytic caps at top left corner of power supply board.

These?
caps.jpgcaps.jpg

#5 3 years ago

Yes. Note that one is + up, the other + down.

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