DIY to fit my need. Finally, it works as expected, but some minor overshoot to about 4.5V at power up, DVM is good to see. Looking forward to see what can I do to mod it better, this is first glance to deal with modification to a DC supply like this, a good start of attempt to.
theory of such 5V supply, major component are TL431 and PC817 for the feedback control loop
seeking help if it is able to resolve easily