Your 5V only needs BR2 and C5 replaced.

Check Connector J101, Pins 1 & 2 in particular. Look for tarnished connectors / pins
Check the Fuse Holder for F133. The fuse should clip into place. Just for something a but different, change the fuse. I've seen fuses cause issues like this. Check the fuse holder has no dry joints.
Continuity between one side of the BR must be Grounded (looks like it is ok)
Check C5 is correctly installed and jumpered
Check pin 1

Other possible culprits

C9 - Could be shorted
Q1 - LM323 has a short between pin 1 and 3

For kicks and giggles

Just wondering if something is dragging down the 5V. Remove  J114, J116, J117 & 118.

Report back !