PSU problem

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dylan666

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Hi all,
I have a problem that eludes me

My PSU had apparently stopped working,
and I've changed it. So the mb and pc are ok as they are now in perfect working order.

The interesting thing starts ---->
Out of curiosity I've started a test on the PSU in question just to determine what went wrong...conclusion the PSU works just fine (all the rails have good quality voltages even if they are fully loaded). This testing was made with no connection to the motherboard (hotwire the green and ground on 20 pin conn.) The fan starts when hotwiring take place).
So back to the drawing board, I've connected the PSU with MB but again the same thing happens the PSU wont start.

Any ideas?
Thanks in advance
 
There are many more issues with a PSU then the 12volt rail only. The only test that makes any difference it that it would not power up your Mobo and the new PSU will. You can't do a load accessment anyway so throw the thing in the garbage where it belongs and forget about it!!
 
Good to see that.....
Thanks for the warning and the link,
exactly what I'm saying to other people,
but no wories I know what I'm doing,
btw it would'nt be the first psu that went major surgery in my house...
And I will find out what has hapened to it one way or the other
 
Ok
little update>
the power suply supervisor+regulator+PWM is SG6105D 20pin IC
link to the datasheet for the part:

http://pdf1.alldatasheet.co.kr/datasheet-pdf/view/90300/ETC/SG6105D.html

and when the supply is offboard meaning not connected to the MB it functions just fine, when I connect the PSU with the MB then it doesn't function properly.
Sample of the mesurement:
OFFBOARD (HOTWIRED):
pin 1 = 0,2 V (logic PSon/PSoff HI/LOW)
pin 20 = 5,25V (supply)
reference pins folowing>
12 = 2,5V
13 = 2,5V
17 = 2,5V
18 = 2,5V
OFFBOARD (OFF)
pin 20 = 5,25 V
pin 1 = 5,25 V
----------------------
ONBOARD (OFF)
pin 20 = 4,0 - 4,2 V ( as you see lower)
pin 1 = 4,2 V (lower)
ONBOARD (ON)
pin 20 = 4,0 - 4,2 V
pin 1 = 0,2 V (as it should be)
ref pins
12 = 0V
13 = 2V
17 = 0V
18 = 0V
----------------------
What do you all think should I try to replace the IC, or is there a problem which I can't see?
 
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