my power supply keeps tripping the on/off switch. this is the yellow all plastic power supply for the diagnostic. i bought a new rectifier and it still trips. i hooked it up to power without the rectifier and it still trips. i put an ohm meter on each side of the transformer and it does not look like there is a break. how can i test the transformer to see if it is causing the tripping, or is it the switch that is bad?