Today I was trying to measure the rectified SMPS incoming power supply ( 315VDC) using a tektronix TDS 3932C oscilloscope with P6139A probe. Every time the ground-probe touches the ground of the supply, the power supply rectifier diode is getting damaged. I assumed it may be related to earth fault current, but both equipment supplies are properly earthed.
I need some advice here.
Eqpt :Tektronix TDS 3932C Digital Phosphor Oscilloscope 300 MHz Probe used: P6139A , 500MHz, 8 pF ,10 MOhms, 10x
Edited I want to check the pwm controller IC O/p waveform with the oscilloscope, the Vcc of the IC itself is tapped from the rectifier supply, and I am unable to use the oscilloscope.