Because the DM8000HD power supply can only be turned on if it was fully connected to the motherboard. And if you're like me, do not become happy when you must connect it to your good working motherboard to see what the power supply does. Now with this solution, you do not have this problem. And is also easier to repair because you can now work/measure outside the box on both sides. But a little more info... The power supply without being connected to the motherboard delivered only 14V. By adding 3.3V to pin 4,. the smd transistor Q200 is powered so that the power supply turns on. The small pcb I use is a dc to dc converter with an adjustable output. The input of the dc to dc converter I feed with the 14V, and the output I have adjusted to 3.3v. And it is connected to the pin 4, so that the PSU turns on. Furthermore, the LEDs are an additional luxury, and not really necessary. Because you must always measure the outputs, or they are correct. Only in case of failure, an LED will not operate. However be careful with the hot zone when the psu has been active. But good luck with the repairs.