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Kevin Buckle
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Help with fault finding after water damage.

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Phone was in a sports bag with a water bottle that leaked. I dissembled the phone (just like the teardown posted on this site Galaxy S3 Teardown).

Left it in an airtight bag with some silica gel for 48 hours.

Cleaned all parts throughly in IPA bath, dried and inspected all connectors, tracks, components etc under microscope, with no visible damage.

Reassembled and everything working perfectly … until I inserted the wall charger. Then the screen immediately went black (including soft keys) and has not worked since.

The phone itself works fine except for the display. I have connected to it with ADB, backed it all up and verified that the touchscreen and soft keys are working fine. I have tested the screen assembly in a different phone and it works fine, so the screen/lcd/digitizer itself is not the problem. It must be a fault on the mainboard.

Due to the initial cause (water damage) and the way in which it failed (during connection of external power), I suspect the problem is power supply related, i.e. the mainboard is not supplying power to the lcd or something similar.

Has anybody seen a similar set of symptoms? Or can anyone tell me which (if either) of the two main power ICs on the main board control the LCD? Or does anyone have a link to a schematic for the board?

I suspect this could be an easy repair if I can find the fault, and may save people the cost and hassle of replacing an entire mainboard if I can provide a "HowTo".

Which model is your SIII:"GT-I9300 GT-I9305 SHV-E210K/L/S SGH-T999/L SGH-I747 SGH-N064 SGH-N035 SCH-J021

oldturkey03,

I am an idiot! Completely forgot all that basic, but essential info. It's a GT-I9300, stock ROM (4.1.2), unrooted, completely unmodded in every way. Baseband version is I9300XXEMC2. If there's anything else I've missed that could be useful just let me know.

Kevin Buckle,

"I am an idiot! " No, you are not. After all, you asked a great question at a great place, actually that makes you pretty smart:-))

oldturkey03,

Thanks ZServices and oldturkey03, that's an awesome couple of responses. I couldn't really have wished for anything better. Armed with the service manual I am sure I can get this thing going. I don't think it's the LCD OCTA ASSY as this carries the touchscreen as well as the lcd, and the touchscreen is still working. It might be seated incorrectly (damaged pin etc) or maybe some corrosion between a pin or two on the pcb socket, so I'll double-check that first as it would be the easiest fix. After that, the service manual lists U706 as a possible culprit, along with U707, L703, L706 and U500. I'm hoping for an 'L' component since I probably have access to some spares right here at work and my soldering skills are good enough to swap one out! If it's an IC, I'll probably need to order something in and get my soldering guru to take a look for me. I'm hoping to take a quick look at lunchtime today, then I'll be working on it over the weekend. I'll report back with my progress. Thanks again

Kevin Buckle,

Excellent, good luck to you.

oldturkey03,

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ZServices
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Hi,

Check this elements:

https://plus.google.com/u/0/b/1168838503...

But i think you must to replace DCDC i.c. (U706).

Regards

Yes - the problem was either U706 or U707, though neither was faulty. See my comment above for a description of the fault resolution. Thank you for pointing me in the right direction :-)

Kevin Buckle,

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oldturkey03
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Kevin Buckle, I added the service manual for the phone to the device page. Scroll all the way down until you find the Service Information paragraph and click on the blue link. This will download the manual with the schematic etc. Amazingly enough the troubleshooting guides first step "Power-on the phone and check the power-on sound or motor biration. Sound or Biration is ok? No--> Change the MEA FRONT-OCTA LCD ASSY So you may be on to something here.

Block Image

Hope this helps, good luck.

Brilliant! The service manual took me straight to it, although in the end it was much easier than I was expecting :-) See my comment above in the original post for details.

Kevin Buckle,

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