HELP: TT Go 910's won't charge

[go930user]

Hi again,

Found the photo!

This was a mod on an after market 910 dock, so I can't be sure about whether or not the circuit card shown here is similar to, or identical with the OE dock circuit card.

I'll reiterate the caution: If you modify a 910 dock so that a high current capacity USB port can charge/run the device, then DO NOT couple the mains charger through it's power socket on the dock at the same time.

Cheers

Go930user

 

[Andy_P]

Another thing I've seen done more than once is to run parallel USB ports for power. Nothing more than a simple Y adapter that sources two ports out to one device.

And another caution, this about Y cables. They are fine if the two USB plugs are attached to two USB outlets sourced from the same USB chip because, from memory, a single USB controller chip handles both power and signal to a pair of USB ports. If you are paralleling the power sources together, you need them to be matched so they do not "fight" one another, but share the load equally between them.

I'd always assumed those Y-cord USB power cables had diodes in them to avoid that problem.

But maybe I'm being too trusting!

 

[canderson]

Nope. No diodes. The voltage drop through a typical diode, even at a decent level of current being drawn, would be unacceptable for many devices, and outside the USB spec as well. It's assumed that it's a common source with minimal potential for differential across the USB power pins. You'll note that they also keep the two "Y" leads short so that you couldn't - for example - pull power off a front and rear port on a tower at the same time, or even a left and right side port on a netbook at the same time.

 

[Andy_P]

Thanks.
Must remember not to use a USB male-female extension on one then!

 

[canderson]

The voltage drop depends upon current being drawn, the length of the wire and wire gauge. As short as these wires tend to be, it might well not even matter at 500mA each.