Pull F2 and F3 and see if one or both blew right away. Your power supply board has had some work in the high voltage area (D3 has been replaced for sure and looks like there might be more work behind the capacitor). I would recap that power supply and get a high voltage re-build if the fuses are still blowing.

Did you measure them with a meter? They are so fine, you cannot visually see when they are blown.

Take a close look at the displays. Look at them at different angles. Look for any hint of orange glow in either of them. If there is orange glow, you know they are getting power.

If still nothing, measure the voltages on power board J2. BE VERY CAREFUL as there is high voltage there that can hurt you. Black lead on ground, red lead on:
Pin 1 -100v
Pin 3 +100v
Pin 5 0V (ground)
Pin 6 +5V

Make sure ALL ribbon cables are installed properly. Are not reversed on one end. Are not one or more pins off. etc

The fact that you need to enter diags each time you power up is an indication your batteries or CMOS RAM circuit isn't working. Probably due to bad or corroded contacts on the battery holder. Resolved by replacing the CMOS with NVRAM and getting those batteries off the board!