Electronics Repair School

Acer Chromebook C871T Series Repair

Started by hkarre, Mar 21, 2024, 07:42 PM

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hkarre

Hi all!

I just wanted to share a success story. I have been watching many different electronics repair videos on YouTube for over a year. I have always gravitated to micro-soldering repairs as they are the most interesting. I currently work in an American K-12 school district where we use a lot of Chromebooks every day. I have many that are out of warranty and need repair but they are made too cheaply to be affordably repaired. Anyway, I thought I would try my hand at repairing, and at first, I failed. I failed a lot. I have the proper tools but didn't understand how to use them. Anyway, I have practiced and practiced and last night, I finally did it!

I had two different Acer C871T series Chromebooks, one of them had a bad screen (cracked, a student broke it), and the other had a damaged USB port and was not charging or turning on when the other USB port was plugged in.

Using a USB-C ammeter I noticed that the laptop that was not charging and had the damaged USB port was drawing somewhere between 200-300mA at around 5v. When I pressed the power button nothing happened.

I opened the case and did a quick visual. Nothing jumped out at me. I plugged the ammeter back in and using an infrared camera I saw that the USB-c controller chip, the ANX7447, was getting hot. I used my multimeter and checked and found that all of the caps surrounding the chip were shorted to ground. I took this as a sign that the chip was not good. So applying flux and having my hot air station set around 400 C with my air around 45% I proceeded to remove the chip. It seemed like it was taking a long time but in the end, I was able to get it removed and I was successful in not damaging the board or any of the other components. The chip is a QFN style.

Just as a curiosity, I wanted to see how the board would respond to power with the chip removed. I plugged the ammeter back in and saw that it was doing pretty much the same thing and since I still had the infrared camera on I spotted another chip that was getting hot! This one was just dumb luck that I found it. Anyway, this one was a little BGA chip next to what I am assuming was the BIOS chip. I removed this one with flux and my hot air station too, but this time I set the heat to 450 C and the air to about 40%. I looked it up later and saw that this was a security chip. This would give me a problem later but I was able to solve it as well.

Next, I removed the motherboard from the Chromebook with the bad screen and I checked the caps around the two chips that I was considering swapping over to the board I was working on. Working quickly I applied flux, heated each chip up with my hot air station, and removed them. Again working quickly, using the same heat and air speed settings, I soldered the two chips in to their new homes. Then I cleaned up and let everything cool down.

After that, I reassembled the components needed to test and plugged my ammeter in, and at first no change then everything reset, and the ammeter came back on and it showed that there was 19v and 2 point something amps current draw! Success! I finished reassembling and testing and I was greeted with a Google Chromebook login!

I am so happy that I can get some of my Chromebook fleet back up and running! I know that this was only my first one but I sure hope that it will not be my last.

Just a note about the damaged USB-C port. This particular model of Chromebook has a separate daughterboard with one of the ports on it. I just ended up swapping this whole daughter over to the Chromebook that I had replaced the two chips on. So now, I have one completely working Chromebook one with a bad screen, two missing chips, and a bad USB-c port on a daughterboard.

Thank you, Sorin, you and several others like you on YouTube, have been kind enough to share knowledge and inspire others to follow and learn.