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Old Oct 18, 2011, 06:12 AM   #1
stedel
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Join Date: Oct 2011
USB drawing too much power on MacBook

Hello,

I have a MacBook 2,1 (Intel Core 2 Duo, 2.16 GHz) which I use with a keyboard, a mouse attached to the keyboard and a rather ancient and VDU ( Mitsubishi Diamond Pro 900u).

Over the past few days I have had several notices saying the a 'USB device is drawing too much power.' My keyboard and mouse get disconnected as a result and I am now using my Macbook's keyboard in conjunction with my VDU. Not ideal as this is my main machine.

I have restarted my machine and unplugged the cable connecting it to my printer.

I read a post suggesting resetting the power management unit but the instructions were for a G5. Does anyone know

1) if resetting the PMU will sort the issue
2) how to reset the PMU on a macbook
3) what else I should do to get rid of the message
4) whether an Apple wireless keyboard and mouse or magic trackpad would be a good solution given the problem?

Thank you

Steph
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Old Oct 18, 2011, 06:34 AM   #2
Makosuke
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Join Date: Aug 2001
Location: The Cool Part of CA, USA
1) Depends on what's causing the problem, but it's worth a shot

2) http://support.apple.com/kb/ht3964

3) If that doesn't help, either there's something wrong with one of your devices and it's actually drawing too much power, or there's something wrong with your MB (likely an internal short on one of the USB ports).

Testing is easy. Try removing (or replacing with a temp) either the mouse or keyboard. If it doesn't help, try removing the other one. If either of those works, you've got a bad device; could be just a loose wire, but probably safest to just replace it.

If neither helps, you might try a completely different mouse/keyboard just to be sure, and also try a different port on the MB to make sure it's not a wonky port that can be avoided.

If none of the above do anything, it's probably a bad wire/port within the MB, in which case you're probably out of luck. There's another thread here with a huge read count and a few additional suggestions you can try (might be the one you already found).

4) If it doesn't complain when no USB devices are plugged in, then yes, that should work fine. In fact, even if it's a bad port and the USB just cuts out, there's a chance it will still work, depending on the port; my MBP has two USB busses, one of which handles the Bluetooth module, one of the external ports, the internal keyboard and trackpad, and the camera. The other just does the IR receiver and the remaining two external ports.

So depending on the configuration of your MB (check System Profiler to see what's going on under the hood), the Bluetooth module could be fine even if one whole bus is flaking out. In fact, if yours is like mine, then if the internal keyboard works there's a good chance Bluetooth does as well, since they're on the same bus.
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