Android touch screen problems when charging

SlateDroid

Screen touch problem when charging.

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cLevel 08 Jul 2012

Hi everyone,

I got my U30GT-H (OEM) from Panada. I have to say that it exceeds my expectations. Now, for people with screen touch problems while charging, I think I have a solution.

Problem: When charging, the screen is unable to correctly map finger touches on the IPS screen. It makes navigation on the tablet next to impossible. Once charging is complete, and is removed, problem gone. Also, people may have intermittent symptoms during charging only, read further..

Cause: POS Power Supply

I originally thought there was a ground isolation issue with the barrel of the plug end (which is NEG-) contacting the metal accessories grill. (I still do, but another story.)

This metal accessories grill (the metal tab with all the ports for sd, hdmi, 2 screws, etc.) is connected (and grounded to) the long metal band that wraps around the tablet, which in turn, is grounded to the rest of the device. That's good.

Theory: Unfiltered EMI from the PS, even attenuated TI from the power cord itself (its an antenna too!) ground itself on the common (and balanced) ground of the tablet. This creates a very noisy electrical field that the IPS screen can not handle (its out of spec, because its a cube design flaw). That's bad.

What I did:

I originally thought by removing the metal grill and isolating the ground that this would fix the problem. Well it didn't, so back to drawing board, and time for another cocktail.

Time to look at the PS. I opened it up and well it was as expected. A cheap, badly soldered, linear power supply with a under performing transformer. VNom was 12.20 volts, during load (charging) -- 10.4 volts. It gets worse (ok non-techies - 10.4 is not that great), after about a few min, I hear a click from the PS board, and look -- wow 3.2 volts -- under charge.

I found a PS from a portable HD which was a 12V 3A. Cut the old cord off, attach old cord to new PS, and plug in and test. ALL PROBLEMS GONE. The new PS is holding 11.89V with load. fantastic. I even put the grill back on, and still NO PROBLEMS. Warning: I do still think there is a design flaw with the power port hole being too small. they (cube) needs to drill that hole LARGER so there is no secondary contact. Its a design flaw -- listening CUBE?

Please, I am only throwing this out there for the community to digest, and comment. My comments are without warranty, are without prejudice, and the views expressed are not endorsed by Cube. (sorry, I have to say it.)

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antonywarsono 12 Jul 2012