Burning sound from the PSU

Question

I am trying to make a bench power supply from an old 350W PC PSU that provides 4 lines

1. 3.3V 8A
2. 5V 9A
3. 12V 11A
4. -12V 1.5A

Here is the connections diagram:

I used this step down module to be able the adjust the voltage and current limit on the 12V and -12V lines: "DC-DC Converter Step Down Module 12A"

I used this display to monitor voltage and current: "DC 0-100V 10A Digital Voltmeter and Ammeter Dual Display"

The problem is that when I try to increase the voltage using the potentiometers of the step down module, I hear a burning sound. I don't know what it is, but I feel like if I don't decrease it fast it will burn something. The burning sound increases very much with the voltage increase

Here is a video for the problem Burning sound

Is the problem from the step down module, or is it from the PSU?

Answer 1

The problem was because of i had installed the step down module on the body of the PSU and a pin of the soldured pins of the step down module was making a short circuit with the PSU body, so i just put an insulator between them :)