bad VCORE pwm in soft start

[laoveja]

Hi i have a Biostar k8m800 micro AM2.
it doesn`t POST and only have 300mV on VCORE.
The PWM Controller in an ISL6568 and after check vcc = 5v and enable (pin ENLL) = 1.2v i think its ok but i dont know what component could be bad. The enable pin is connected to pin 15 of ATPA01G (no datasheet).
Theres a pin PGOOD that indicate the status of the controller. its always low but i dont know if its by an fault or its always in soft start. i dont know where could be the fault. the caps dont look bad. any idea? i really want to learn how to fix mobos and this is the hardest that i try. thanks

PWM Controller:
http://www.intersil.com/en/products/...s/ISL6568.html

POWER CHECK:
http://es.aliexpress.com/item/ATPA01...224449455.html

[laoveja]

Re: bad VCORE pwm in soft start

PWM Controller:
http://www.intersil.com/en/products/...s/ISL6568.html

POWER CHECK:
http://es.aliexpress.com/item/ATPA01...224449455.html

[cmia]

Re: bad VCORE pwm in soft start

post some pictures please
can a mod move this into the motherboard section please.

[momaka]

Re: bad VCORE pwm in soft start

I agree with cmia, post a picture of *your* motherboard here (use forums built-in feature, NOT off-site such as imageshack or whatever).

You could still have bad caps but they might just not be showing it. From what I've seen, BioStar really liked to use Chemicon KZG capacitors on the VRM low side on some of their motherboards. If that is the case with your, a recap would be highly recommended.
However, given the problem, it could also be a bad FET on the VRM. With the CPU removed, check the resistance between Vcore and ground and Vcore and 12V rail on 4-pin 12V CPU connector. Let us know what you get.

[Sparkey55]

Re: bad VCORE pwm in soft start

I agree with cmia, post a picture of *your* motherboard here (use forums built-in feature, NOT off-site such as imageshack or whatever).

You could still have bad caps but they might just not be showing it. From what I've seen, BioStar really liked to use Chemicon KZG capacitors on the VRM low side on some of their motherboards. If that is the case with your, a recap would be highly recommended.
However, given the problem, it could also be a bad FET on the VRM. With the CPU removed, check the resistance between Vcore and ground and Vcore and 12V rail on 4-pin 12V CPU connector. Let us know what you get.

I have seen OSTs on BioStar mobos also.

[momaka]

Re: bad VCORE pwm in soft start

Me too, but usually on the RAM and chipsets' rails.