Barely perceptible flicker on Pixelbook
TL;DR: Fixed a board by replacing the display connector and traces for the backlight. Now backlight sorta flickers.
Side Note: This is mostly an exercise in stretching my troubleshooting and micro-soldering abilities - Pixelbooks aren't worth much, though I do have a replacement on order because my wife still uses it pretty often.
Background: Coffee was spilled onto the display connector of a Google Pixelbook which (of course) managed to short out the display backlight. This burned the connector on the main board and the cable. In fact, it burned two pads for the connector too.
So, some time later with a hot air rework I managed to salvage a display connector (and screen, cable, chassis, etc) from another dead Pixelbook (seemingly bad RAM or CPU, couldn't figure that one out). I also got a new wire run to the two backlight pins (2,3). How do I know they're the backlight pins? It is clear on the donor board they're connected together and I accidentally connected them to ground on my first attempt and the screen worked but the backlight did not. Anyway, everything works!
Except...there's this slight flicker to the backlight. It doesn't turn off all the way, just flickers dimmer and brighter. Doesn't seem to be related to screen brightness (does it on low or high), and it doesn't do it all the time, but it does do it most of the time. It doesn't seem related to screen position, or physical movement of any sort.
Three options:
1) Display connector isn't making good contact. Despite my efforts with IPA, there's still a lot of (Amtech no-clean) flux in it. I could put the board in an ultrasonic cleaner, though I've struggled to get this flux off other things. How do people get this stuff off of boards, particularly from hard to reach places like inside connectors?
2) My fix isn't great. Maybe too small of a wire, maybe only one of the two pins is making a connection. Maybe one pin is flaky. The size of these things (and lack of a microscope) is limiting my ability to test my work.
3) Something else in the backlight circuit went bad during the Great Coffee Spill. Not sure how to go about finding that.
4) Something else?
Since I have a donor board, theoretically this is fixable, as long as the bad component isn't a BGA or something.
Thoughts on where to go from here?
Side Note: This is mostly an exercise in stretching my troubleshooting and micro-soldering abilities - Pixelbooks aren't worth much, though I do have a replacement on order because my wife still uses it pretty often.
Background: Coffee was spilled onto the display connector of a Google Pixelbook which (of course) managed to short out the display backlight. This burned the connector on the main board and the cable. In fact, it burned two pads for the connector too.
So, some time later with a hot air rework I managed to salvage a display connector (and screen, cable, chassis, etc) from another dead Pixelbook (seemingly bad RAM or CPU, couldn't figure that one out). I also got a new wire run to the two backlight pins (2,3). How do I know they're the backlight pins? It is clear on the donor board they're connected together and I accidentally connected them to ground on my first attempt and the screen worked but the backlight did not. Anyway, everything works!
Except...there's this slight flicker to the backlight. It doesn't turn off all the way, just flickers dimmer and brighter. Doesn't seem to be related to screen brightness (does it on low or high), and it doesn't do it all the time, but it does do it most of the time. It doesn't seem related to screen position, or physical movement of any sort.
Three options:
1) Display connector isn't making good contact. Despite my efforts with IPA, there's still a lot of (Amtech no-clean) flux in it. I could put the board in an ultrasonic cleaner, though I've struggled to get this flux off other things. How do people get this stuff off of boards, particularly from hard to reach places like inside connectors?
2) My fix isn't great. Maybe too small of a wire, maybe only one of the two pins is making a connection. Maybe one pin is flaky. The size of these things (and lack of a microscope) is limiting my ability to test my work.
3) Something else in the backlight circuit went bad during the Great Coffee Spill. Not sure how to go about finding that.
4) Something else?
Since I have a donor board, theoretically this is fixable, as long as the bad component isn't a BGA or something.
Thoughts on where to go from here?