after having plugged the power-adapter with inverted supplies (19.2V +/- swapped) into the ASUS U5F notebook of my wife (you'll understand the severity of the problem), it has burnt a little bit and since then the USB (maybe the 5V supply) seems to not work correctly anymore (the rest seems to be ok).
To investigate the problem until now I found out the following:
- the schematics of the mainboard are not available
- the device seems similar to the Asus U5A (no schematics available either)
- at least one component has burnt (as pictured below)
- I'm unable to identify what this component is doing exactly, so I can't replace it
- the components is of probably packaged using "SOT-223-4"
- the marking code is 8C609 (I could read it before cleaning the section, now there is only "8C6" left)
- I suppose it is a LDO-regulator, but I don't know the exact reference
EDIT: The question now has a follow-up.
Best Answer
Your best bet is not to identify what part it is, but what function it had and replace that function. You will have to unsolder the part anyway. After that, you can start working out if and how it is connected to the USB port. If it is, you know what it does and can replace it with something else.
It is possible USB might work after you unsolder the part. Perhaps it is just some peripheral part, not the power supply to USB. In this case, the fried part might just be shorting USB power, which then shuts down.
If not, maybe (danger!) you can connect the USB 5V directly with Mainboard 5V from, say the harddisk plug. This would change how safe USB is (usually it is limited to a certain amperage), and you could fry the notebook with USB. But then again it is already toasted...
Usual warnings etc: dont burn down the house.