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From: Al on 27 Oct 2009 04:03
Hi Guys,

I have got a mobo here that is dead. I have done all the usual stuff
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 headers
from the power on switch and the ATX header on the mobo that tells PSU
to start up.

I am trying to find this IC.

I have attached a image of the mobo with some of the IC's that seem
possible labelled.

http://www.badcaps.net/forum/attachment.php?attachmentid=12082

Interested to know if anyone knows which IC controls the PSU and tells
it to turn on? Someone else suggested this function was handled on the
CPU since P4, but I am not sure about that.

Thanks


-Al

RT9237 : http://www.alldatasheet.com/view.jsp?Searchword=RT9237
93705CF : http://www.ic2ic.com/search.jsp?sSe...3705CF&prefix=9
952001AF : http://www.alldatasheet.com/view.js...chword=952001AF
2N03L : http://www.alldatasheet.com/view.jsp?Searchword=2N03L08
LD117 : http://www.st.com/stonline/products...fo/ld1117_1.htm
RT9602 : http://www.alldatasheet.com/view.jsp?Searchword=RT9602
From: david on 27 Oct 2009 04:19
On Tue, 27 Oct 2009 01:03:07 -0700, Al rearranged some electrons to say:

> Hi Guys,
>
> I have got a mobo here that is dead. I have done all the usual stuff
> 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 headers
> from the power on switch and the ATX header on the mobo that tells PSU
> to start up.
>
> I am trying to find this IC.
>
> I have attached a image of the mobo with some of the IC's that seem
> possible labelled.
>
> http://www.badcaps.net/forum/attachment.php?attachmentid=12082
>
> Interested to know if anyone knows which IC controls the PSU and tells
> it to turn on? Someone else suggested this function was handled on the
> CPU since P4, but I am not sure about that.
>
> Thanks
>
>
> -Al
>


I would check first that you have the power button wired correctly.
From: Grinder on 27 Oct 2009 05:09
Al wrote:
> Hi Guys,
>
> I have got a mobo here that is dead. I have done all the usual stuff
> 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 headers
> from the power on switch and the ATX header on the mobo that tells PSU
> to start up.
>
> I am trying to find this IC.
>
> I have attached a image of the mobo with some of the IC's that seem
> possible labelled.
>
> http://www.badcaps.net/forum/attachment.php?attachmentid=12082
>
> Interested to know if anyone knows which IC controls the PSU and tells
> it to turn on? Someone else suggested this function was handled on the
> CPU since P4, but I am not sure about that.

If you short the power button pins on the motherboard's front panel
header, will it start up?

I'm sorry I can't be more specific about where those pins are as I don't
know what motherboard you have. (I don't have a badcaps.net login.) If
you identify the motherboard, I can give you a more specific answer.


From: Desk Rabbit on 27 Oct 2009 05:47
Al wrote:
> Hi Guys,
>
> I have got a mobo here that is dead. I have done all the usual stuff
> 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 headers
> from the power on switch and the ATX header on the mobo that tells PSU
> to start up.
>
> I am trying to find this IC.

Assumming you can identify the chip, and assuming you can safely
unsolder it without breaking the board and assuming you can solder the
new one in without breaking it or the board, I'd suggest a new mother board.

> I have attached a image of the mobo with some of the IC's that seem
> possible labelled.
>
> http://www.badcaps.net/forum/attachment.php?attachmentid=12082

Give us a login and we will be able to view that.
From: Paul on 27 Oct 2009 11:34
Al wrote:
> Hi Guys,
>
> I have got a mobo here that is dead. I have done all the usual stuff
> 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 headers
> from the power on switch and the ATX header on the mobo that tells PSU
> to start up.
>
> I am trying to find this IC.
>
> I have attached a image of the mobo with some of the IC's that seem
> possible labelled.
>
> http://www.badcaps.net/forum/attachment.php?attachmentid=12082
>
> Interested to know if anyone knows which IC controls the PSU and tells
> it to turn on? Someone else suggested this function was handled on the
> CPU since P4, but I am not sure about that.
>
> Thanks
>
>
> -Al
>
> RT9237 : http://www.alldatasheet.com/view.jsp?Searchword=RT9237
> 93705CF : http://www.ic2ic.com/search.jsp?sSe...3705CF&prefix=9
> 952001AF : http://www.alldatasheet.com/view.js...chword=952001AF
> 2N03L : http://www.alldatasheet.com/view.jsp?Searchword=2N03L08
> LD117 : http://www.st.com/stonline/products...fo/ld1117_1.htm
> RT9602 : http://www.alldatasheet.com/view.jsp?Searchword=RT9602

Any chance of posting the badcaps image, on one of the free image hosting
sites ?

In terms of your notion of figuring it all out, based on a picture,
that isn't likely to happen.

I have three reference schematics here, and they all implement that
function in a different manner.

First off all, there is a whole chain of logic associated with that
function. It includes the Southbridge (Wake on USB keyboard, Wake on
scheduled RTC time, Wake on PME from PCI bus), the SuperI/O
(Wake on Ring on serial port, Wake on PS/2 keyboard keypress), plus
some external jelly bean logic. Those chips contribute reasons why
the power should be switched on.

One schematic, uses a 2N3904 transistor as the interface to pin 14
on the 20 pin ATX power connector. The interface is open collector
logic, so a transistor can be used as the driver.

Another one, uses a Fairchild 14 pin TTL logic chip, with open
collector output drive, to control the signal on pin 14.

The third schematic uses a custom chip, with no data available,
to drive the signal directly.

So even if you do post a picture of the motherboard, and the
resolution of the picture is high enough to read all the chips,
it still may not be possible to guess at the method. Chips don't
have to be placed in proximity to the driven thing. So you
won't necessarily see the "guilty party" sitting right next
to the 20 pin connector. There is no requirement in a layout,
that a driving chip be placed right next to the load. It
could be all the way across the motherboard, on the other
side of the board.

Paul
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