820-00165-A logic board MacBook Air

[mferna14]

Just received a 820-00165-A logic board, liquid spill on it. I cleaned very well (ultra sonic cleaning). Turned the logic board on & at once the display fuse F7700 blew (BURNT). I saw green stuff on the LCD connector J8300 (pin 3 & 4). As it was corroded & backlight related., On the safe side I replaced U7701, the fuse & the connector. Again turned on the fuse did not blow, the logic board turned on & I get all the voltages, but as soon as I see the backlight on the LCD screen the logic board turns off by itself. I Checked the vollatge 3.3V & 8.52V on F7140 is present but the 5V rail on L7520 is not present at all. Then again I put the Magsafe jack, turns on fine, fan spin well but after few minutes it just shuts down. VIN is present on chip U7501 8.5v on pin 23. Any tips will be greatly appreciated. Thanks in advance.

[piernov]

Re: 820-00165-A logic board MacBook Air

Shutting down with LCD disconnected too? Tried known good Magsafe, DC-in board, DC-in board FFC?
Always take note of the affected area before cleaning.

[mferna14]

Re: 820-00165-A logic board MacBook Air

Yes, the logic board shuts down even if the LCD harness cable is not connected. I am trying with know good part by replacing them but no luck, its shut down. I took a note of all the corroded components & viewed under microscope but no broken trace or such, all connections & soldering seem to be good.

[mferna14]

Re: 820-00165-A logic board MacBook Air

Ok., I figured out why was it shutting off automatically after a few moments. Actually there was a slight corrosion on the BIOS chip too & the pin 5 trace was broken to the resistence. Upon a cleanup & installation of the BIOS chip from a donor board, all works fine & does not shut down any more. I installed it in the unit with its SSD, it OS boots up half the way & hangs up. Even with my know good OS it does the same, just hangs up after half OS boot. Any reason why, or any tips on this, do you think the BIOS chip from the donor is bad??? Thanks for all the help anyways.

[piernov]

Re: 820-00165-A logic board MacBook Air

You have to clean ME region.

[mferna14]

Re: 820-00165-A logic board MacBook Air

Thanks I will do so...

[mferna14]

Re: 820-00165-A logic board MacBook Air

I did the ME Region clean.... I got the clean BIOS program from Badcaps site. Now what happens, I get all the Voltages, CPU core 1.5, 3.3, 5V & all, I observe that the CPU is running in the background as it get hot but still there is no fan spin & no display. I get 5V on pin 1 of J6000. Have I missed certain rail voltage which I have not come across? Your help will be much appreciated. Thanks

[piernov]

Re: 820-00165-A logic board MacBook Air

I'm confused. You said it was turning on but it was hanging while booting macOS.