Here's a photo of the area just north of the PSU components.

The pair of blue jumpers (upper left) should measure 5.0 - 5.5VDC. If not, remove the jumpers, and measure from the right-hand pair of pins there. If still not, then the 5V supply is not working.

The single black jumper (upper right) beside that metal tab thingie is for the +3.3V supply. Again, it should measure about 3.3VDC. If not, remove the jumper and measure from the topmost pin. If still not 3.3V, then the 3.3V supply is not working.

That'll do for starters..