820-3209 keeps burning current sensing resistors

[2informaticos]

Capacitors from charger area maintain voltage some time.
Onboard measurments on ohm scale are not relevant untill these caps are discharged.
You've got confused and R7086 never got blown in fact.

Keep battery disconnected, untill get the board working correctly with charger alone.
Check diode mode to ground on all big coils; compare readings with known good board.
Be aware, as CPU coils can have low ohm value to ground as normal.

Do you get stable 3V3_S5/SUS?

 

[Narek]

You've fot confused and R7086 never got blown in fact

That's right, I just wasn't waiting enough long to let caps discharge..

Do you get stable 3V3_S5/SUS?

Yes, they both are stable 3,3v.

Some other readings:

SMC_RESET_L - 3,3v,
PLT_RESET_L - 0v,
AP_RESET_L - 0v,
PM_SLP_S3_L - 0v

Diode mode readings on big coils:

L9701 - 0,385v
L7260 - 0,366v
L3895 - 0,475v
L7220 - 0,400v
L7030 - 0,130v
L7100 - 0,007v (13ohm to ground), another board I have has 0,014v and 28ohm to ground
L7630 - 0,007v (13,9ohm to ground), another board I have 0,15v and 28ohm to ground
L7330 - 0,184v
L7550 - 0,001v (2,4ohm to ground)
L7510 - 0,001v (3,5ohm to ground)

 

[2informaticos]

Still quater fan spin now?
If yes, check for pulse at all big coils.
Also check ALL_SYS_PWRGD.
SMC bypass mode changes something?

 

[Narek]

Yes, still quarter fan spin. All big coils except L7550 are pulsing. ALL_SYS_PWRGD is 0v, in SMC bypass mode fan spins once and stops, then again.

 

[2informaticos]

Do not get any pulse at ALL_SYS_PWRGD, at same time coils pulsing?

 

[Narek]

It's pulsing too, gets to 3,3v then drops. But board doesn't pulse every time I connect charger. Sometimes it just doesn't react at all, sometimes it's pulsing.

While measuring ALL_SYS_PWRGD on R2584 it turned on twice, behaving like while normal board start - CPU got warm, fan was speeding up because of no trackpad connected. After I took probe off R2584 and touched it again, board turned off then started again. I replugged charger and now it's just pulsing.

 

[2informaticos]

Random behaviour change is not easy to diagnose.
There could be broken trace/solder under some BGA chip.
Try reballing SMC first.

 

[Narek]

Try reballing SMC first.

I've already done it in beginning of the thread. I'll relpace it this time.

 

[Narek]

I've replaced SMC and it seems that it was the problem. Except first 2 tries when board didnt react for charger, now after SMC reset it seems OK - turning on, charging and working on battery, loading OS correctly. I will test it today and report if problem has been solved.

 

[Narek]

Replacing SMC solved the problem, computer works stable for few days already. @2informaticos thank you for your help and patience!

 

[2informaticos]

You're welcome, glad to hear is done...