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820-3115 CPU core appear for 1 seg

M

MDY

New member
820-3115
I found burnt transistor or mosfet (3 pin chip) on dc jack on 820-2565 dc jack board.

I tested main board with another dc jack but same story. CPU core appear only for 1 seg at 1.12V
I compared all coils with another board 820-2879 and only found differen value at L7260. In faulty board I have 0.173 in diode mode. Red in ground
In working board I have 0.400 in diode mode. Anything more I can measure?
 
M

MDY

New member
I checked the board and it is not liquid damage. I reflowed with flux rom and clock chip but no change.
 
M

MDY

New member
Board for i5 and i7 have same bios, right? I mean 3115 is only what I have to look in donor board, right?
 
M

MDY

New member
Also without bios this board will loooping right? Now it is not looping. CPU core appear for a seg and fan speed for a seg. Nothing more.
 
D

dukefawks

Administrator
All 3115 BIOSes are the same and should work for testing. Watch out the China parts boards may have the BIOS chip erased!
 
M

MDY

New member
It is not china board. Comes from a macbook I didnot repair weeks ago with another problem. I was told 3115 board has PCH ussual problems, but I never tried to replace that. What do you think?
 
D

dukefawks

Administrator
This could be anything if it is not liquid damage. The usual suspects when it was liquid damage is the clock chip or crap under SMC. I very much doubt this board "just" stopped working.
Put back the original BIOS to avoid ME region problems and replace the clock chip.
 
M

MDY

New member
I checked again the board and found bad looking C4921. I replaced with solder (no heat arround) and now works and power. Make sense C4921 to stop the board from power?
 
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