USB has power but do not recognize any USB device. (Nothing to do?)
Hello guys, I have an iMac 20" (Early 2008) and, about a month ago, I turned it off at night and in the next day as I turned it back on it booted fine but the mouse and keyboard (USB) wasn't working (besides the red led under the mouse were well lit) and from now on it doesn't recognize any USB devices (I can tell it has power because it charges my iPhone even though it does not recognize it on Mac OS). Bluetooth, which should an option, with a wireless mouse and keyboard doesn't work either (same USB bus?). I can boot to CD/DVD or external drives since the keyboard do not work and PRAM and SMC reset does not appears to work since the keyboard is not "present". That said, anyone has an advice (besides "change your logic board") for me on this? Thank you in advance!
I got a tip that it should be a Southbridge chip solder problem. I'm inclined to try to reball it with a hot-air gun, like I did in many xboxes and HP computer earlier. Is there a way to anyone point out where is the Southbridge on these iMacs logic board?
With the data part of your USB ports being out and the bluetooth not functioning (bluetooth is piggy backed into a USB channel) and things charge from the USB ports, that says you have multiple USB channels with power but no data transfer. More than likely the Southbridge on the motherboard has been compromised or died. Your solutions are:
1) Send the motherboard in for repair. A number of places on eBay will do it for $250 USD or less, with a warranty.
2) Replace the logic board.
If you go for the repair, I would make sure they replace the part or reball it - not reflow. Not that I am against reflow, it actually works miracles done right. The vast majority of the people with the skills and equipment capable of consistently doing a good reflow prefer to reball to remove all ghost and protect their reputation. They also will replace the part if it is bad.
This is what they look like:
This picture is from a different board than yours. But the Southbridge has a very distinct look. The chip pad it sits on is comparable in size to the CPU. So it is one of the biggest chips on the board.