Nabi2 - Red & Green Blinky/No Blinky

No good deed goes unpunished...

Last fall I happen to find at my local used electronics store 3 Nabi2 and 3 NabiJr learning tablet computers for $240, less than half price new.  We had been talking about getting them for my son's school last year and just never happened.  I jumped on the deal, picked up some spare power cords from Amazon, and brought them into school.

Since I first got them, the charging for the Nabi2 (a 7" tablet) has been spotty, I ended up having to return one "OEM" charging cable to Amazon because it wouldn't charge the tablets.  A couple weeks ago one of the teachers complained the tablet wasn't charging at all, so it became my next victim.

The tablets use a bizarre and non-standard 0.7x2.6mm barrel plug, the first problem.  I tried again to charge it at home and no charge light would come on and the battery was dead, wouldn't turn on more than to show a empty battery icon.  The case opens with four little screws on the back, at each corner behind the red bumps on front, and a little ginger prying (there are 3-4 snap closures per edge).  Once inside, I found the culprit, the charging jack was actually cracked.

Inside the Nabi2 with new jack charging.

The Nabi charges at 2A, but still uses a USB style power controller that detects if the voltage drops below the 5% spec of 5V.  I cut apart the "OEM" cable and found a rather cheap plug that was poorly soldered, and 26AWG wire, which at 3 feet long and 2A, has about a 0.5VDC drop.  So unless you're using a really hot 5.25V USB charger (which isn't completely unusual, most are 5.1-5.2 to account for voltage drop under load), it likely wasn't going to work and the tablet would just blink red-green to indicate charging error.  I verified this as a cause by hooking it up to my bench power supply to which I can limit the output current-voltage, 5V and 1A limit wouldn't charge and 4.7V and 2A wouldn't charge either.  Luckily, I picked up a 5VDC, 2A Raspberry Pi power supply with 20AWG wire and some new plugs, and wired that up for a dedicated charger.

The parts are available at:

http://www.mcmelectronics.com/product/27-9848 for the jacks and

http://www.digikey.com/product-detail/en/cui-inc/PP-012/CP-012-ND/408474 for the plugs

A word of caution, unsoldering the old plug is a pain, partly because of the flimsy tabs on the power jack and also because they glued the jack onto the board with some red adhesive during factory assembly.  I actually damaged the positive landing pad and had to scrape of some of the green conformal coating adjacent to solder on a jumper for the new jack.

Power jack next to the microUSB slot