820-3437 Board Couple Second Fan Spin Few Times then Boots Normally

[mdc2018]

820-3437 Board

Originally No Power - was Missing PP5V_S4RS3.

Replaced U7501.

Now have PP5V_S4RS3 measuring normal 5V with fan spin, then after couple seconds fan stops& voltage drops to zero . Machine keeps trying to start like this and fails.

Fas spins for few seconds then turns off.

Keeps trying to boot.

After 5-7 attempts it boots normally.

On DC meter it pulls around .6A then goes to 0 on each failed boot attempt, then stabilizes at around .3A when successfully boots.

Wondering if someone recognizes these symptoms and can tell me where to check next, i'm relatively new at this.

Thank you.

 

[2informaticos]

When charger is connected for the first time, machine should restart twice, before stays on.
Is the normal behaviour for 3437 board.
Next time must turn on directly pressing power button, if battery is present; or charger not disconnected.

Restarting 6 times is not normal.
At least confirm if always happens, or just first time charger is connected.
Any history available, liquid signs?

 

[mdc2018]

I can confirm It does always happen (usually boots after 5-7 unsuccessful attempts) . Signs of light liquid damage yes. Upon another inspection of the board I see solder balls coming out of the side of bios chip U6100. Would a bad U6100 cause these types of symptoms?

Also I understand you cant simply change these, there is a process involved regarding "ME Region" (?)

 

[2informaticos]

If machine works good when starts (not slow), ME region should be good.
But is better to write new dump, clean ME.
Make a backup and upload it somewhere.
Also post the serial from bottom cover, just in case.

 

[mdc2018]

Assembled machine fully & did smc reset - now it appears to be working perfectly. Boots normally each time.

Thank you!