Here's how I do it
Set DMM to VAC
Turn Machine On
Black to Ground
Red to J1 Pin 1 & 2 ~12 VAC
Red to J1 Pin4 & 5 ~14 VAC
Black to J1 Pin 6
Red to J1 Pin 7 ~69 VAC
Turn Machine Off

yes it does. they will run a little high without load

A2P2 is the 5VDC right? Use this schematic and work your way back to the regulator. You can see where the genius who made this schematic (not me) put in the expected voltage at each point. http://www.stevechannel.com/images/tech_tips/System1PowerSupplySchematic.jpg

You might find that it is correct at 1 point and then bad at the next. That would indicate the component needs to be replaced. What I'd expect here if the regulator is putting out 5v is the SCR101 or CR101 is shorted.

Turn it down. The worry is it's too high and the protection circuit is pulling to to ground to protect the mpu.

After you turn down the 5V you have to work backwards from A2P2 P1 and test at all the places on the 5V line.

In the attached image I have labeled the points you can test (1 to 4 circled) and the expected VDC to see where the voltage may have dropped.
pasted_image (resized).png

Work backwards from A2P2 P1 to the junction of CR101 and R4 (5V adjustment pot) and measure there. You may need to poke around with the machine off to find someplace to test. My guess would be the center lead of the pot but see if it has continuity to CR101 before you use it as a test point.

If you find you have 5V at 1 place but not the next the component closest to A2P2 is suspect.