So on "BOTH" displays digit 5&6 13&14 are both dead when I turn the machine on.
After about 20 seconds digit 6&14 on BOTH displays is up working, bright and crisp.
After about 90 seconds digit 5&13 on BOTH displays is up working, bright and crisp.
As this is happening exactly the same on both displays I don't believe the issue is the display glass. It must be coming from a shared/common point most likely on the MPU.
1J1/4 - Strobe 5 - both Displays
1J1/3 - Strobe 6 - both Displays
1J2/4 - Strobe 13 - both Displays
1J2/3 - Strobe 14 - both Displays
So I replaced U44 no difference and then U51 on the MPU but again no difference.
The resistor arrays on the MPU SRC 7, 8 & 9 all measure ok.
I have checked the cable/header connections and all seem fine.
Once it's working you have to leave it off 3 or 4 hours or overnight before you get the issue again.
Thoughts? What am I missing?