Re: Power controller chip to turn on ATX

>
>
> > On Wed, 28 Oct 2009 10:18:59 -0700 (PDT), Al put
> > finger to keyboard and composed:
>
> > >> Al wrote:
> > >> > I have got a mobo here that is dead. I have done all the usual stu

ff

> >> > like trying new PSU, bench testing etc. Its dead - as in no fans,

no

> >> > nothing when you hit PWR button - PSU doesnt even come on.
>
> > >> > I connected the ATX molex from the PSU and shorted Green (PWR ON)

with

> >> > GND on the molex and the PC came on. All seemed fine.
>
> > >> > I think there is a IC on the motherboard between the PWR BTN heade

rs

> >> > from the power on switch and the ATX header on the mobo that tells

PSU

> >> > to start up.
>
> > >> The MB circuit only tells the enable circuit inside the PSU to let t

he

> >> PSU turn on. To what voltage does the PWR_ON (green wire) fall when

you

> >> push the ON/OFF switch? The MB must pull this wire lower than 1.5v f

or

> >> the PSU to turn on. I have seen enable logic failure modes where, fo

> >> example, 1.2v would not turn the PSU on, but 1.0v would. Check that
> > >> voltage level before replacing any ICs on the MB.
>
> > >When I hit the pwr button that voltage level doesnt change.....(and
> > >the switch is fine)
>
> > What are the standby voltages at the on/off pins on the motherboard
> > header? If there is no +3.3VSB or +5VSB, I would check the LD1117
> > linear regulator near the ATX Molex connector.
>
> > FWIW, my old socket 7 motherboard uses an SiS 5597/5598 all-in-one
> > chipset. The chip has an ONCTL# output pin which controls the PSU's
> > PS_ON input, and a PWRBT# input pin which appears to connect directly
> > to the on/off "power button". This is debounced internally by the
> > chipset by means of a 30ms delay. The 4 second off timer is also
> > handled internally by the chipset.
>
> > SiS5597, Silicon Integrated System, Pentium PCI/ISA Chipset:

formatting link

>
> > - Franc Zabkar
> > --
> > Please remove one 'i' from my address when replying by email.
>
> Hi Franc,
>
> Excellent suggestions. There is 5v on the On/Off headers.
>
> This motherboard (ECS L4S5MG/561) uses the SiS561 chipset
> (northbridge?) but whats the other chipset under the black heat sink?
> southbridge?
>
> How do I work out the number of the other chipset short of degluing
> it?
>
> -Al

Found it: SiS651 North Bridge and SiS 962L MuTIOL South Bridge chipsets.

Now I need to see if one of those chips controls ON/OFF switching. If it does then probably chipset dead?

-Cheers

-Al