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That was good that you checked the power voltages on the power connecting Molex on the bottom of the backplane.
It certainly shows that your power supply is fine Mark.
1st off, that may just be an informational message and not really an "error"?
Try checking that 2-wire black/red power harness that runs down to the VFD driver board attached to the back of the door panel.
The driver board is the one with the ribbon cable running up to the VFD display.
You will notice it has a black and red 2-pin harness powering it up.
Disconnect the 2-pin black harness plastic plug by depressing the housing latch inwards to release it from the header socket.
Turn the cabinet's power switch ON, and check with your multimeter the voltage coming out of the harness.
Finally, it's NOT good that the MPU LEDs aren't coming on.
That pretty signifies some sort of possible fatal fault on the MPU.
Why isn't the MPU getting power although your backplane is powered up?
Do you have a 50X series MPU, a 1270 MPU, or 044 version MPU?
Also, certain backplanes have a pair of blue fuses....check those if your backplane has them.
The problem with burnt fuses is that, it takes a short somewhere, to blow one.