Hi Nic,
I'll cc this to the viphone list, since the last part of this post is
about USB power usage and charging for the iPhone, iPod Touch and
iPad. I'm not sure I qualify with respect to knowing a lot about
hardware, USB devices, and electricity, but I'll try to answer your
question, although I've never had OS X shut a device down with a
message that it was drawing too much power. However, I did just make
a recent trip where I had to troubleshoot one of the USB ports of a
MacBook. Devices that were plugged into that port didn't work
properly: printer cables wouldn't relay signals to the attached
peripheral, iPods would not be recognized by iTunes, and a plugged in
mouse was evidently powered (lit up), but not enough to register
clicks on the machine. All these devices worked correctly when
plugged into the other USB port. Power cycling with restart and
repairing permissions didn't help. (I only tried the permissions
repair because the Software Update had just been run to install a
security update before the problem behavior.) What did work was
resetting the PRAM, which apparently restored the USB port to its full
power. If the source of your problem is not the aging of your
headphones but the USB current support from your computer, this fix
might help. I'll give you the instructions I received from Apple's
Tech Support, since they're slightly different from what is in the
Knowledge Base article.
1. Power down the computer and remove the battery from the MacBook.
(On my model you need to get a thick coin, like a U.S. nickel, to
insert in the slot of the lock for the battery, and give it a quarter
turn clockwise to rotate it into the unlock position so the side of
the battery near the lock will pop up, and so that the battery can be
removed.)
2. With the battery removed, hold down the power button for at least
12 seconds.
3. Replace the battery. (On my model, you insert the side near the
left edge of the laptop so that it engages, and then swing the other
end so that it slots into the lock position. Then you use the coin to
turn the slotted lock a quarter turn counter-clockwise to lock again.)
4. Hold down the Command, Option, P, and R keys while you power on
your laptop. I press down the Command, Option, and R keys with my
left hand (little finger on the Option key, ring finger on the Command
key, and either middle or index finger on the R key). I press the
thumb of my right hand on the P key and push down on the power button
with the middle finger of my right hand.
5. You need to keep the Command, Option, P, and R keys pressed for at
least 3 start-up chimes before releasing them in order to reset the
PRAM.
6. Log in as usual and check your USB port connections.
This fixed all the problems with the USB ports. I think, because the
mouse was being powered, but not enough to register clicks with the
system, that full power wasn't going to one of the USB ports.
I'll point you to the Apple Knowledge Base article on "Apple
Computers: Powering a peripheral through USB":
http://support.apple.com/kb/HT4049
Computer USB 2 ports are supposed to be rated for 500 mAH. That's
less than the 1000 mAH you'll get from an AC outlet (in the U.S.) with
a USB charger for the iPhone or iPod Touch, which is why charging your
device on the computer's USB port is slower, and which is also why the
earlier iPods and iPhones could charge from FireWire connectors that
didn't have the same limitation. Apple shifted the standard connector
for its iPods and iPhones to USB2 because most Windows computers
didn't have FireWire (a.k.a. IEEE 1394) ports. This is the source of
some of the battery charging error messages that are seen with some
iPhone cases -- all devices are now supposed to use chargers that
adhere to the more limited current capacities for the USB2 standard.
This is also the reason why some 3rd party batteries will take a long
time to charge an iPhone if they only supply 500 mAH of current. I
suspect that this is also why some cases, like the Mophie JuicePack
Air, require you to discharge the secondary battery before draining
the main iPhone battery for maximum charging use, since most batteries
do not maintain power regulation as they discharge and may go out of
the regulation specs. (This is of interest to me as an iPod Touch
owner, since Mophie just came out with a JuicePack Air for the iPod
Touch -- however, it appears to disable the internal speaker whether
or not the earbuds are plugged in when the iPod is in the case, and
also appears to disable use of the volume, start/stop, and voice
control functions of the headset earbuds that com with the iPod Touch
3GS if they are used while the device is in the Mophie JuicePack Air
case. This is based on user comments for this product at the Apple
Online Store.) Incidentally, the 10 W Power Adapter for the iPad will
charge iPods and iPhones, as well as the iPad (which draws 2100 mAH).
However, the iPad will apparently not charge (even slowly) off the USB
ports of non-Mac computers, and when connected to a Mac's USB port
(not through a keyboard USB port, and not through a hub), may even
give a message that the device is not charging (although, if you wait
long enough, it will charge).
From the same Apple Knowledge Base article that I linked above,
here's the information about USB charging on newer Intel Macs:
"On some newer Intel-based Macs, such as the MacBook (13-inch, Late
2007), when a device requiring more than 5V and 500mA is connected,
the port with that device connected to it becomes a high-powered port
capable of offering up to 1100 mA at 5 V. That port will continue to
operate as a high-powered port until the device is removed. "
That same Knowledge Base article (about USB charging) is referenced in
a link in the Knowledge Base Article about "iPad: Charging the battery":
http://support.apple.com/kb/HT4060
HTH
Cheers,
Esther
Nicolai Svendsen wrote:
Hi guys,
So, I'm looking for someone here who knows a lot about hardware,
specifically on the Mac-side and someone who knows a lot in
particular about USB-devices. Oh, and electricity, perhaps.
Here's the deal.
I've got a Skype Wireless Freetalk Headset, the old model. I've been
using it for a while with no issues at all. Eventually, my Mac would
disable the device because it said it was drawing too much power and
had to be disabled.
The headset setup consist of a round-shaped small box with one
button to turn off the receiver completely, and to pair it properly
to the receiver and the headset. On this box there are two buttons,
one extending to the plug of a USB and the other extending to a
small, round plug which plugs into the right side of the headset for
charging. Both of these aforementioned wires both extend away from
the round box. When I get the message above in a dialog box, the
headset promptly turns off because there is no signal being received
from the USB port as it becomes disabled, and when touching the wire
charging the headset, it becomes boiling hot. The USB wire feels
fine, but all the way from the point from which the wire to the
charger extends, to the plug that goes into the headset for
charging, becomes incredibly hot and almost impossible to touch.
My question to those knowing about this type of issue is this: Why
would this happen after a year or so of using this headset just
fine? Is it because the wire is broken? If that is the case, why
could I use it for a couple of hours prior to this happening today,
regardless of twisted the wire became?
Thanks, and I'd be grateful for any advice.
Regards,
Nic
Mobile Me: nic2...@me.com
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