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Acer Iconia A200 repair Rate Topic: -----

#1 User is offline   aotsukisho 

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Posted 22 April 2016 - 05:00 PM

I recently received a tablet that was not working; it would not turn on, and there was no charger included. Fixing the Kindle Fire a couple years ago proved to be a success, so I thought I'd give this one a try as well.

After some research, I found that it was an Acer Iconia Tab A200 model, and that a relatively common solution to them not turning on was simply to open it up, and manually detach and reattach the battery cable.

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Here's the tablet name, model number is printed on the side of the tablet

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Use a small flathead screwdriver to pry off the trim pieces and access the screws on the side.

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Here's the trim being popped off completely.

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Same on the other side, but this time it's in two pieces.

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First look inside the tablet, there's not too many things different in architecture between designs.

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Here's a look from the other end.

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The 4-pin double red and double black connector goes straight to the power jack on the side, which is what I'm most interested in at the moment.

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I removed one each of the negative and positive leads, in order to attempt to charge the battery this way. The AC adapter is supposed to be rated at 12v @ 1.5A, so I tried hooking it up to the output from a spare ATX power supply. No response.

Next step is to check the battery...
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#2 User is offline   aotsukisho 

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Posted 26 April 2016 - 02:38 PM

I removed the battery plug and pulled out one each of the positive and negative pins to hook up to my RC battery charger. The lipo is a 7.4v one, and unfortunately I don't have the pinout (and am not comfortable with opening up the packaging) so I won't guess which of the other three wires is the balance tap. I charged it up to around 80% or so and stuck it back into the tablet. The Iconia booted up, but I was presented with this...

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When entering recovery mode, I would get this every time. For search engine spiders and such, this is the error in text:

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Erasing Userdata...
Unrecoverable bootloader error (0x19000008).

Enter recovery mode by holding the Vol+ button (furthest away from the corner) and pressing the Power button until the white LED turns on. Immediately release the power button, and flick the rotation-lock switch back and forth until the screen goes to the one above.

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How do you solve the above problem? You do the above process repeatedly until it goes away. No joke. It took me 9 times, some users have reported it taking up to 15 times.

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After setup is completed, here's the stock home screen.

I also ordered a cheap 12v charger off of Ebay, so we'll see when that comes in.
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#3 User is offline   aotsukisho 

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Posted 27 April 2016 - 03:50 PM

Due to me taking forever to actually upload the last post, here's what happened a week or two after the time the events in the previous post occurred.


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While fooling around with the jack hoping the lack of charging was just a bad connection, the positive wires detached. Yay.

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Soldered it back on at work, which is difficult with a 60W chisel tip iron

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Unfortunately while testing the repaired jack, this happened. I'm not really that perturbed by it considering I got the AC adapter for around $4, but the tiny gauge of wire concerned me so I decided to open the adapter up.

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Closer view of the prongs pulled out of the shell. I am aware that this is a tiny adapter rated for only 18W or so which equates to around 200mA at the wall, but still.

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Because this charger was so cheap, I did not care if I would cosmetically ruin the casing. Hammer away!

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Here's what it looks like inside. I immediately began to worry about the design of this circuit after a single glance.

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Top view of the board, there's a large amount of that white goop

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Closeup on the bottom of the board. It immediately struck me as strange how the output of the AC adapter was soldered to the bottom, and there was a large solderblob of stuff in the bottom left corner. I dunno wtf that is next to Z1 in the center, and the soldering job securing the wires from the AC prongs is so laughable I could have done better in my sleep.

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In case it's not blatantly clear what I'm going on about the pcb being 'suspicious', take a look at the topside of the corner where there the two solderblobs were. Large solder pads with through-hole large gauge wires generally means that this was the intended output wires of the circuit, and for whatever reason the actual 12v output on this adapter was being pulled off before the final output of the circuit.

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Immediately desoldered the output cable from the adapter pcb, and this pcb will be under further investigation later. I gave my pocket oscilloscope to my brother so I am not able to do output analysis at this time, but I suspect that there is significant ripple voltage that is giving the Iconia's charging circuit trouble.

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Soldered to a lipo battery connector for now for testing purposes

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Unfortunately the same flashing white status LED occurs a few seconds after plugging it in to my molex AC adapter used for my external optical drive, so either this AC adapter has ripple or voltage drop issues too, or the problem lies elsewhere.

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Confirmed to be voltage related, as hooking it up to a true regulated 350W PC power supply and with a low ESR 1500uF/16v capacitor used in filtering the Xbox360's CPU voltage added near the connection did not result in a stable charge.

The reason why I initially thought that ripple voltage was an issue was because after disconnecting it from the molex AC adapter I tried plugging the Iconia straight into a 3s lipo sitting at around 12.6v and the power LED in the tablet stayed orange. After testing on multiple PC power supplies and obtaining the same result with all of them, I have concluded that ripple is not the problem but apparently 12v is too low of a voltage for the charging circuit to work properly.

I posted in the Acer community forums asking if an automotive 11-15v is safe for use to charge the tablet, but as of the time of this posting I have not generated any responses.

I will see if I can find a 12.5 or 13v power supply to test, but for now the tablet is just sitting on my desk.
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#4 User is offline   aotsukisho 

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Posted 12 July 2016 - 03:09 PM

Getting real tired of this tablet's bullshit.

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Soldering a tap on the positive input from the charging jack, and pulled out the contacts that go to the motherboard.

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Soldered a tap onto both of the positive battery wires

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Shoved it all back into the stupid tablet chassis

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Now I can charge the battery straight from the jack as an unbalanced 2s lipo. Because of the atrociously high internal resistance of the components (plug, jack, connectors) I can only manage a measly 600mA maximum charge before the apparent voltage the charger sees maxes out at 8.4v.

This thing has caused more headaches than its usefulness. On top of it being such a pain in the ass to charge the battery properly, it's not the fastest tablet and has problems running anything at the same time it updates things.

I think I'll just use it like this until it dies. Sigh
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