Another broken tablet

Some time ago I got another new Android tablet - this time just about the cheapest one I could find with sensible specifications. This was essentially meant to be plaything for our kid so I didn't want to invest too much money as I expected it to be treated badly. So I ended up with Acer Iconia One. From start I could tell that the build quality wasn't exactly great - it felt flimsy and plasticy, in short pretty much what you'd expect from cheap device.

Well, it took about two weeks until it broke the first time. Unfortunately this happened at Thailand, in middle of our two-week stay. I have absolutely no idea what happened it but display suddenly started to show some very serious "ghosting" symptoms and became very dark. Even after full power-off and even factory reset it showed traces of image shown before these. Very weird. At home I took it back and it was replaced for warranty. No problems with that since.

Now it stopped charging completely. The USB port showed signs of bad contact already before this, but now it became completely dead. So I took a closer look:

Again, through microscope with phone camera so bad quality, but I'm pretty sure you can tell that this is one unhappy USB connector. No wonder it's dead.

I suspect that this would not be covered by warranty so I didn't even bother but took it apart. Insides weren't surprising - one PCB, battery, display with touch, speakers, cameras, microphone and that's just about it. PCBs have become smaller since the last time I opened one but all the major parts are there still.

Start from top left and proceeding down and right the connectors are: Display, touch, cameras (two of them, one facing front, one back), Micro-SD, buttons (four buttons, but only three of them are exposed outside enclosure), battery, headphone and the USB.

Bottom side is fully covered with tape (no components at all), to avoid shorts as this is placed directly on top of display module. There is combined GPS/WiFi antenna on the back cover, connected via the connectors you can see there above the audio jack.

Speakers and microphone were soldered on pads; those you can see at lower left and right side of board. Cheap, cheap...

Underneath leftmost can (which ended next to camera connectors) there was mystery BGA chip with marking 8539 (left to Flash chip on picture) I couldn't find any information about, and then there is a switching regulator - very likely to drive display backlight.

Underneath next can were Hynix Flash chip, two memory chips, Mediatek ARM processor (next to memories) and Mediatek MT6323 which appears to be power management IC.

Last can I didn't open, I expect radio to be there. So in all nothing too exciting, and really - this is pretty much what every phone or tablet has these days. More expensive devices use just a larger memory that costs few dollars (!!) more, and/on few dollars more expensive processor with a bit better specs. Maybe a bit better camera and more refined build quality.

I just can't but wonder how much of the "cheap" external feel of this is actually very deliberately planned and designed to encourage shopper to go for a bit more expensive model with "better" feel, with exactly same parts inside...

But back to the USB.

Surprisingly the USB connector was a bit sturdier than most I've seen in these devices - this actually has through-hole pins that hold it on the PCB better. Unfortunately I didn't have exactly the same connector handy, but I had one close enough to work. But first, taking the old one off.

Hint: If you have trouble desoldering lead-free solder apply some new leaded solder there first. This will bring the melting point of combined solder down a bit, making the process a bit easier. This makes especially the ground pins in middle of large ground planes so much easier to desolder cleanly.

I first wicked most of the solder away from the through holes with desoldering braid, then used hot air (at 350 degrees C) to melt solder enough to allow connector to be lifted out. After that I cleaned the holes and pads as well as I could:

The mounting hole pitch wasn't the same with new connector, so I straightened rear ground pins and then cut the one pointing towards audio connector shorter, as the partially desoldered pin you see there, middle one, right next to USB pin, is not ground but some other signal. I wouldn't want to short that out.

The small chip you see there next to USB pads is very likely some common mode filter to reduce interference. It's placed uncomfortably close to USB, making soldering the pins difficult, but with some flux, patience, steady hand and thin solder tip I managed. Not the prettiest job I've done but it works, and hopefully lasts a bit longer than the previous connector. I deliberately went a bit overboard with solder on ground pins; more solder should make the mechanical connection there a bit more harder the break with stress.

And now I have a working tablet again, with just about a hour of work.