[REQUEST] Mystery: re-seating kills chromebook?

[Nicholas Roth]

I have an Acer Chromebook 14 CB3-431 on my desk right now. This is the first laptop that I am repairing (I have done many desktops and repaired other machines that are designed for easy maintenance). My friend knows that her laptop might simply end up dead, as this is my first laptop.

The problem is a flickering / unreliable monitor. The behavior changes based on the angle of the monitor and gentle pressure at the bottom can temporarily correct the issue. After taking the protective cover off of the laptop monitor, I found that gently wiggling the EDP cable connecting it to the motherboard always would correct the issue temporarily. At this point, the problem was narrowed down to something in the cable, something in the monitor-side connector, or the small control board built into the monitor.

My first step was to re-seat the cable on both ends. I turned off the chromebook with a hard reset, unplugged the battery, and re-seated both ends of the monitor cable. After plugging the battery back in, the machine appears completely dead. I see 4V across the battery connector itself, but nothing at several points on the motherboard that I tested. The power light that is typically blue is also off. I do not have immediate access to a charger, or I would've tried booting up on external power only.

Does anyone here who works on laptops know what may have happened?

 

[coffee]

First is, Its not sitting in front of me so my help will be limited to guessing.

If you plugged in / unplugged the screen cable with the battery in or the charger then you probably damaged the screen circuit on the motherboard. If your absolutely sure that you did not do this then its possible that a couple wires in the screen cable shorted and also took out the screen circuit.

Testing this, Remove the battery and the screen cable from the MB. Then plug in the charger and see if you get any lights. If you are not getting any lights then look for the power button connector on the MB and with a meter check for 3.3v on one of the pins by putting your negative lead on a ground and checking each pin. If you have no 3.3v then also check for 5v the same way on a USB connector and ground. If you do not have either then it is possible that the laptop has detected a short on the MB and is not permitting it to turn on.

If you do have the voltages there then ground the pin on the power button connector briefly on the MB that has 3.3v on it and see if it powers up - fan spin.

I will guess to say that you do not have 3.3v on the power button nor do you have 5v on the USB cable. These are "Always on" voltages so the laptop does not have to be "on" for these voltages to be there. If they are not there then you need to check if the 19v main rail is present.

Its very common to accidentally plugin/unplug the screen cable and not realize that you left the battery connected. There are fuses on the screen circuit. These are 0 ohm resistors that are designed to blow if something goes wrong. However, These would not keep the laptop from power up. An actual short in the screen circuit would though.

Also, Price out a new MB. If the laptop will not power up with the screen and cable connected then the problem most likely is in the MB. Chromebooks are pretty inexpensive and you might just have to replace the MB.

 

[nerd2u]

What's the retail on that model?

I have to ask why even bother paying to fix it when you can get a new one for like $200?

My labor cost alone would be half the price or more of a new one.

Sent from my SM-G870W using Tapatalk

 

[HCHTech]

First is, Its not sitting in front of me so my help will be limited to guessing.

Haha - Love you new avatar! Some days I definitely feel like Barney!

 

[Porthos]

Haha - Love you new avatar! Some days I definitely feel like Barney!

It thru me off, like who the hell is this. I has to think twice..

You get used to the avatars of the regulars.

 

[HCHTech]

You get used to the avatars of the regulars.

Now I read his posts with Barney Fife's voice in my head - still chuckling.

 

[coffee]

Its for Holloween

"The Ghost and Mr. Chicken"