820-00165 Fan Spins twice ,No Chime, No Video

[Don Anton]

Hi,

This is not a liquid dmg board. Board is pretty clean

I have all the power rails including vcore.
Fan spins for 5 sec then stop and spins for ever.

Clock chip signals are fine but replace the clock chip, SMC, test with different bios to see whether it chimes still same behaviour. Put back the original bios.

Check current sense resistors and they all good and measurements are fine.

also No light on usb mouse.

Any adivice greatly appreciate.

 

[2informaticos]

Check if both PLT_RESET_L and PLT_RST_BUF_L stay high.
Also check voltage on the L/C blocks between CPU and edge board.

 

[Don Anton]

Hi Thank you for your quick reply.

PLT_RESET_L and RST_BUF_L are 3.3v
L/C Blocks get 1.V all of them

 

[2informaticos]

This looks like bad CPU.
Did you try clean ME BIOS?

 

[JohnB8812]

Bad CPU have had this fault many times sadly

 

[Don Anton]

Hi Huys,

Just to let you know I replaced the CPU on this just to find whether I can solve this as I got 4 of them same /similar issue. Still behave the same way fan spins for 5,6 secs and fan runs for ever with vcore present no chime no video no usb response. So fa I replaced SMC/ Bios/ PCH/ RTC/U1950.