Quoted from Nihonmasa:
Nope, but I am 100% sure it’s not the display.
I did this test to confirm it: (yes it’s bad to plug/unplug while power is on but...)
boot up machine, have misIng digits as usual
Remove all connections to display
Display stayed completely disconnected from the machine for 10 mns
Replugged display => all digits were there
So it clearly is on the board side that i have an issue
Sounds power supply related. Can you test for (+5) and voltage at the power supply right when you power up the game and then test again after it's been on for 10 minutes, checking for a difference? I suspect when it first powers up, you will see a lower supply.
The new display should only need 5VDC to operate and I suspect there is a problem that resolves itself as the game warms up.
Wouldn't hurt to try and locate a 5VDC test point on the new display as well. Not certain there is one but you can probably find a place to check it.
Since you are using a new LED display, the game no longer needs HV for the displays... You can remove that fuse on the power supply if you like. It will run a bit cooler and the power plug supplying voltages will be stressed much less, having less tendency to char and become brittle.