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

[gcain]

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.

 

[dukefawks]

CPU Vcore on L7310 coming on?

 

[gcain]

Trying to find documentation for this board.

Will get back to you shortly.

 

[gcain]

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.

 

[gcain]

PP5v_s5 is stable at 5.04v
PP5v_s4 drops to 0v every four or five seconds.

 

[gcain]

U8170::4 drops to 0 every few seconds.

This controls PP5vS4_EN.

 

[dukefawks]

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]

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.

 

[dukefawks]

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]

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]

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]

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?

 

[dukefawks]

Here is a locked 3662, good enough for testing I guess. If it works we can fix your original BIOS.
https://drive.google.com/open?id=0ByfhQ_x0v-tZLWZfM3VZT3Q1WWs

 

[gcain]

Thanks for that!

 

[gcain]

This board came back to me finally.

Flashed the bios, exactly the same behaviour.

Sometimes only one fan spins. :/

 

[gcain]

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]

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]

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.

 

[dukefawks]

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.