John read the link I sent in post #16 re the Power Supply 101 it will give you all the refs to volts the PSU puts out and you can measure them at the leads or the board if it is still hooked up.

Just make sure you use a digital multimeter and not an analogue one as they inject voltages into the system one is measuring.

The voltages are or should be within 5% either way + or - of the stated voltage. So for example on the 12v rail it should fall between 11.4v and 12.6v or out of that range they make the machine unstable.