Yes indeed there is an lm339 IC present there, I'm gonna take a pictrue to the pcb front and back, and will post it here.

 

 

Like i said, unolder pin 4 and link it to pin7.
Also pin16 is being used as overcurrent, and can be altered if needed.

Ideally the wire on pin1 should be screened to pin7.

 

what do you mean "the wire on pin1 should be screened to pin7." ?? , and if I wanted to disable the OCP circuit then I have to ground pin 16 right ?

 

If you want to override the current yes ground pin16, i would leave it for now. The wire on pin1 , is better using screened cable and connect the Screen to pin7 ground.

 

do you mean to reduce the EMI effect ? that's why I should use a screened cable ?

 

I have modified these before with this chip. You have to fool the Ovp sense on pins 3,4,6, by fixing them at 3V on pin 3, 5V on pin4, and 4 to 6v on pin 6, by using preset pots, i used two 4K7 pots across the 5V chip supply pins 1,12 and the wiper to pin3, and pin6, set them to 3v and 4v, and desolder pin4, and connect to pin 1, this disables the 5V ovp.

When all this is done remove all resistors on pin 14, and put a 10K variable resistor across the 12V output ,wiper to pin14, this will give you your variable supply. If sucessful change the output capacitors to 63V.

Pin 5 is the current sense pin, you can temporary link it to gnd for testing when you get it to give out 28V.

Hello , I have the same psu (Y-B200ATX Ver.3.0) and i want to modify the output from 11.9V to 12.5V 5A current (dont care for the 5 & 3.3V) could you show me how on a circuit drawing please. I'm not that good in electronics.
Thanks

 

I made it , thanks to your posts , by adding 9K ohm to R60 in series and 1K ohm to R62 , now it puts 12.36V perfect for my application , I'm using it to charge 3 cell 18650 Batteries without over charge protection (12.6V is max for the pack) i'm also adding a timer relay circuit (from aliexpress) so when Ac power is off no back power will go to PSU from battery pack .This is a much efficient solution than solar schottky diodes.
Thanks again

 

it looks like nobody knows about this chinese 2003 IC.

too bad ...

Tread carefully when increasing the 12V rail - the 5V ones often have 6.3V electros that don't give you much wiggle room when you turn the wick up.

 

Will do , thanks again

 

Will do , thanks again

Had some networking laser driver units with separately regulated rails from the PSU boxes - can't remember the brand name, but its a device "type" that may be worth closer scrutiny.