820-3437 no boot or USB activity, S0 state but fan does not spin up normally

Paul Daniels

Super Moderator
Not the first time I've had this symptom on 820-3437 ( testing with 85W genuine MS2 ). To date I think I have 3 boards in the "unsolved" box all exhibiting this.

Instead of the fan doing the on/off/on/off... on-and-run sequence, the behaviour instead is to run the fan continuously for the about the same period as the normal on/off/on/off, and there is only a very -slight- change in RPM when it would normally turn off during the first "off" period.

USB stick will flash *once* when the final on-run state is started, nothing more.

From what I can ascertain, all rails are present, platform reset is present, CPU is at 1.7V

I've tried with a known working BIOS, and even gone and replaced SMCs just to see.

Anyone encountered this failure mode before and found a cause?
 

Paul Daniels

Super Moderator
Thanks, I'l give that one a try just, who knows.

Unfortunately no history on any of the boards. Only quirk that they share is they're all came in "clean" (no liquid damage)
 

Paul Daniels

Super Moderator
UPDATE: Sadly, as anticipated, no change in behaviour with a new BIOS and flashed with the known-working image.
 
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