First alphanumeric out on both displays on Earthshaker

[Mfresh]

I've got an issue where the first alphanumeric on my Earthshaker don't work on both of the displays (which are one above the other) , but the rest of the alphanumerics on both displays are fine. The display board is relatively new and has been working fine for a few years.

I have swapped the ribbon cable for a good one and that makes no difference. Not really sure what to check next. Any ideas?

Thanks

Paul

 

[russdx1]

Sounds like the digit select line is bad.

 

[Mfresh]

Thanks. That sounds interesting. What is the digit select line and how do I go about testing/fixing it? Any help gratefully received!

 

[russdx1]

From memory (someone like @AlanJ would know this better) but that ribbon cable basically carries data to select 1 digit at a time and also select which segments are lit. And then scans each digit setting the segments but does it super quick so looks like everything is lit at once but it’s actually only one digit at a time.

So if one whole digit is dead it’s usually the select line or transistor or something that drives the whole digit which has failed.

 

[Mfresh]

Traced the first alphanumeric data line back to the CPU board and cleaned the pin on 1J1-1and it's all working again. Thanks for your help @russdx1.

 

[russdx1]

Fantastic