820-3662 - Fans spin for a few seconds over and over.

gcain

New member
As in the title the fans spin for a few seconds then stop. Then spin a few seconds then stop and so for ever.

Laptop looks absolutely spotless. Customer said it has been in a cupboard for a couple months.
 

gcain

New member
Sorry, I thought I had the info for this board. Had it confused with the 3332 for a second.

L7310 is very unstable. It goes from 1.7v down to 0 and back up.

PP5v_S0 @ C7310 keeps dropping out.
 

dukefawks

Administrator
Power cycling.....Could be absolutely anything if there is no water damage. Inspect for corrosion or damaged/missing parts. This kind of behavior usually does not "just" happen.
 

gcain

New member
So the problem is not with U8170?

The board is spotless, no corrosion what-so-ever.

Just to be clear, only the 5v rails are power cycling and only from PP5vS4_EN.

pp5v_S5 is stable.
 
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dukefawks

Administrator
Why would U8170 be responsible, it is just SLP_S5 cycling? The whole board is power cycling and this could be anything. Unless you can find a clue this thing will be a nightmare.
 

gcain

New member
Hang on, I think I'm missing something here.

The whole board isn't power cycling. PP5v_S5 (and the 3v lines) is rock solid stable, only PP5v_S4 and onwards are cycling.
The power going into U8170 is stable, but the PP5v_S4_EN coming out is going up and down.

If the board keeps loosing the 5v_S4_EN signal, wouldn't this cause the 5v power rails above S4 to keep dropping out?
 

dukefawks

Administrator
Yes that is called power cycling. S5 is of course fine. My verdict still stands, this board is a rabbit hole without any clues to what happened. Could be corrupt BIOS if you want to try that, backup the original!
 

gcain

New member
OK thanks.
Been a steep learning curve on this board...

Do you happen to have a bios binary for the 3662 with a clean ME region handy?
 

gcain

New member
This board came back to me finally.

Flashed the bios, exactly the same behaviour.

Sometimes only one fan spins. :/
 

gcain

New member
When I connect power I can hear something softly go Click-Click, then a second later the one fan starts spinning. Maybe something is tripping?
 

dukefawks

Administrator
I have no idea. If Vcore is pulsing too then it could be about anything. Check termination resistors to U6100 and see if power good signal comes from U1950.
 

gcain

New member
Yes, VCore drops to 0, then tries again.

With U1950, I can't get an ALL_SYS_PWRGD signal though... Might have found something here.


PM_S0_PGOOD keeps dropping to 0v too.
 
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dukefawks

Administrator
ALL_SYS must be present else there would be no fan spin or Vcore even. This could be anything at this point. Only things I can say is to inspect for corrosion again and missing/damaged parts. I doubt this "just" happened in the cupboard.
 
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