TENMA - 72-13610 - DC Power Supply, ADJ/Fixed, 335W, 5A/32V

i am going to modify another smps this smps used to power a vga display through this dc jack this smps has a minor problem which i will show you in a moment its normal output voltage is 14 volt 1.43 amps this smps uses ti stl-431 which is a voltage reference ic can be controlled using two resistance only we can call this a voltage divider i will replace this voltage divider with a potentiometer so that i can vary its output voltage let's turn it on that's the mains input voltage some ec voltage also present in its output as far as i know this voltage might not harm you but it can harmful for sensitive circuit components connecting in earth wire will solve the problem i am connecting this unused hardware can you guess why this problem arrives after connecting the earthwire there is no ac present in its output so we solve this problem easily now let's check its output voltage which is fix