Friday, August 19, 2016

Laptop mainboard - ALMOST right

My last post was about a laptop mainboard that I dropped in, and that it only had one thing different - a different connector for the feature buttons.

Well, then I noticed that the touchpad buttons didn't work.  And it didn't think there was a battery plugged in.  And the LEDs up front (power, battery, wifi) weren't lighting.

I opened it up again, and found that there were no switches installed on the mainboard for the mouse. I surmise that it was for a slightly different model that had buttons in the touchpad (there is also a populated connector on this mainboard in the right place, which is probably for that purpose).  So I got the hot air out and removed the switches, and moved them. I also desoldered the LEDs from the old board and moved them (no mean feat - they are 0603 LEDs).  I plugged in enough to power up, and no luck. The LEDs didn't light, and the mouse buttons still didn't work.

I compared the boards and determined that the mouse button switch leads go through a couple of 0603 100 ohm resistors. One was still on the board, so I moved that one. The other one was probably lost when I swept the switch off with the hot air, so I put in a 330 ohm resistor which I have on hand. This worked.

The LEDs, probably a similar story because I noticed that it had LEDs already in place elsewhere on the board and those were working. I just drilled three holes in the top of the laptop to let the LEDs shine through and covered it with tape.

The battery - that was another story. Turns out the battery connector was about 3mm shorter on this board than the other one. I did manage to remove the connector from the old one and get it on the new one. This took over an hour. Lead-free solder is a pain in the ass when desoldering large connectors with through hole physical stakes.  On the old board, I ripped the via rivets out while desoldering, so I was super careful on the new board. I tried hot air on the old board first but it was just not working and I decided if I was going to have to use other means on the new board, best to practice on the old one first.

Anyway, that's all working now, the LEDs are shining through the lovely bodged holes drilled in the case, the battery is charging, and the mouse buttons work.

I would NOT have been successful at this stuff without the microscope that I bought last week. The parts are just too small for my eyes.  I think they're probably too small for anyone's eyes when you consider you need to examine the solder after your work is done. Maybe you could do it with a 10X loupe but I'm happy to have the microscope.

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