In article <1159256568.411677.186830@b28g2000cwb.googlegroups .com>,
saturnlee@yahoo.com wrote:
> My sister knocked off one of the tiny resistor R175 that next to the
> FW82801AA south bridge. I tried to find the resistor in the computer
> case, but couldn't find it.
>
> Now the USB port is completely dead, windows detects the USB port(shows
> it in device manger), but nothing show up after i plug the usb devices
> in. The mouse and modem don't even light up the LED.
>
> The board is compaq part#:157126-102
> SPS - proc Bd ( w / o ) proc BMW - 2 , intel 810, 4 PCI, no AGP, with
> sound
> Question: Is it possible to detemine the resistor R175' s value?
>
> I look at the layout and guess it may be 22ohm. Any suggestion?
> will it work if i just bridge it without any resistor?
>
> If anyone knows the value of R175 right next to the south birdge,please
> let me know.
>
> Pictures
> http://www.geocities.com/saturnlee/R...ompaq810/2.JPG
> http://www.geocities.com/saturnlee/R...ompaq810/1.JPG
This will not be a lot of help, but here goes...
Reference schematic for Intel 810/ICH0. PDF page 20 has most of
the USB related stuff, and page 14 shows where the page 20 stuff
connects to the ICH0.
http://www.intel.com/design/chipsets...ex/S290657.pdf
Datasheet for ICH/ICH0 82801AA/82801AB. The above schematic
uses 82801AB, and perhaps you can note whether there are
any significant differences by looking at this. There
are some pinout differences between the AA and AB chips,
with the AA multiplexing some signals, while the AB has
separate pins. The differences may not affect the USB.
http://www.intel.com/design/chipsets...s/29065503.pdf
Looking at your pictures with the resistors labelled, the
Intel schematic does have 15K ohm pulldowns on the USB
data signals, and 15 ohm series damping resistors. Your
measured value of 22 ohms could be a series damping
resistor with a slightly changed value compared to
the reference schematic.
If your theory is correct, one USB port should still be
working (as its two 22 ohm resistors would be intact), while
the second port only has one of the D+/D- signals connected
to the USB stack, due to the missing resistor.
Good luck,
Paul