KC Micro Tronix
Member
I encountered a LB that did not have a back light (or display any image data) but powered up all the rails and entered a "SO" state.
I was told "no liquid damage" and I am thinking "Yea right" They all have liquid damage. I spent a few minutes looking at it under the microscope and could not find a single drop of water damage anywhere. At that point I new I was in for something strange. Time to whip out board view and Adobe and see what I had cooking.
I checked the board and found that "EDP_BKLT_EN" was missing, Jumped over to L8304 to find that "PP3V_S0SW_LCD" was not present. Confirmed that "EDP_PANEL_PWR" was also not present and thought crap. I must have a bad CPU.... I have only been working on MacBooks for about three months so I am somewhat of a newbie but I was sure that EDP_PANEL_PWR should be on. That comes directly from the CPU so I thought I was done for. I put in my notes "possible bad CPU" and sat the machine aside.
A few days later not wanting to give up on the board I decided to replace the Bios. I did not have another exact same board in stock but did find the same series board that had the same CPU but only had 4G of ram. I used that board"s "known working" bios to flash this one and changed the SN so it would match the machine.
I totally expected this to be a total waste of time but thought what the hell. I need to rule this out. After flashing the board I powered it up and saw the usual green light and fan spin and I put my meter on L8304 and waited for the initial boot sequence. To my surprise I watched it boot up and go from 0.0 to 3.3V. I said OMG and I shut down the board and hooked up a screen and It worked! I ran apple diagnostics and the machine passed! OMG !!
This is my first LB that had a defective bios. I would of never thought this would fix anything. Has anyone else seen strange bios failures?
I was told "no liquid damage" and I am thinking "Yea right" They all have liquid damage. I spent a few minutes looking at it under the microscope and could not find a single drop of water damage anywhere. At that point I new I was in for something strange. Time to whip out board view and Adobe and see what I had cooking.
I checked the board and found that "EDP_BKLT_EN" was missing, Jumped over to L8304 to find that "PP3V_S0SW_LCD" was not present. Confirmed that "EDP_PANEL_PWR" was also not present and thought crap. I must have a bad CPU.... I have only been working on MacBooks for about three months so I am somewhat of a newbie but I was sure that EDP_PANEL_PWR should be on. That comes directly from the CPU so I thought I was done for. I put in my notes "possible bad CPU" and sat the machine aside.
A few days later not wanting to give up on the board I decided to replace the Bios. I did not have another exact same board in stock but did find the same series board that had the same CPU but only had 4G of ram. I used that board"s "known working" bios to flash this one and changed the SN so it would match the machine.
I totally expected this to be a total waste of time but thought what the hell. I need to rule this out. After flashing the board I powered it up and saw the usual green light and fan spin and I put my meter on L8304 and waited for the initial boot sequence. To my surprise I watched it boot up and go from 0.0 to 3.3V. I said OMG and I shut down the board and hooked up a screen and It worked! I ran apple diagnostics and the machine passed! OMG !!
This is my first LB that had a defective bios. I would of never thought this would fix anything. Has anyone else seen strange bios failures?
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