Earthshaker
Williams, 1989I have an Earthshaker that has a peculiar display issue. One of the digits on the lower display remains active so long as there is activity on the lower display. And from what I can tell, it's taking every digit thats currently being shown on that lower display and superimposing (or combining/overlapping?) everything into that one single digit, causing it to be very bright. What do I need to look at to solve this?
Have you tried to replace the ribbon cable first to rule that out?
I've repaired displays, just not this particular display problem. I'm just not certain with the limited info you've provided at this time that this symptom is specific to a display board problem, and not a cable or MPU problem. Looking at the schematics, U17,U18,U19 and U20 are the specific ICs that are tied to display two. You'd need a scope or logic probe to investigate the signals on those ICs. There is detailed testing information here:
See section "More Segment Problems: the UDN7180 chip"
http://techniek.flipperwinkel.nl/wms11/index3.htm#display
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