820-3787 - Chime loop wich battery

[rvanpruissen]

This board works fully (in limp mode / 800MHz) when the battery is disconnected. When the battery is connected it chimes repeatedly, so at the end of the chime, it chimes again. A different battery produces the same result. Replaced ISL6259, didn't help. Any thoughts? Could this be GPU related?

 

[rvanpruissen]

Assuming you mean safe mode (holding shift), same behaviour. Both current sense circuits measured fine when I replaced the ISL.

 

[2informaticos]

NO, I exactly mean SMC bypass mode; explained many times on the forum how to do it.
Google can help you, in case forum search not...

 

[rvanpruissen]

It won't let me do that, it starts instantly when I press the power button. Only thing I have left to try is corrupted BIOS maybe? Any other ideas?

 

[rvanpruissen]

17/18: 3ohms
27/28: 20,9 ohms

Known good battery tested, same behaviour.

 

[2informaticos]

Does the board start on battery only (no charger)?

 

[rvanpruissen]

Yes, it starts on only the (known good) battery. Same behaviour.

 

[2informaticos]

What is the fault history?

 

[rvanpruissen]

According to the customer it just started doing this, no specific history.

 

[2informaticos]

Monitor SMC_DCIN_ISENSE and SMC_CHGR_BMON_ISENSE levels.
Any sign of corrosion around SMC?

 

[rvanpruissen]

Ok, I started testing for the suggestions above, but noticed the heatsink got hot real quick. Turns out phase 1 of the GPU is pulling ±35A from the start. GPU problem? I'm confused as to why that VR would even start at this point during POST/boot.

 

[2informaticos]

GPU should have the same behaviour for start sequence, w/ or w/o battery.
Check the mentioned sensors level and post PPBUS_G3H voltage with both battery and charger connected.
Is the battery charging?

 

[2informaticos]

With 1.7-2.6A through R7150, CHGR_BMON should be higher than 0.05V.
ISL6259 gain for BMON is 36X.
2.6 x 0.005 x 36 = 0.468V which should get there.
Your problem could be ISL6259, or SMC...

 

[rvanpruissen]

So, I've been struggling with this one over the last few days.
* Replaced ISL > No change
* Replaced SMC > Didn't work (possibly faulty SMC)
* Replaced SMC with 3662 version and clean BIOS > Same behaviour (this one is just for testing, as I don't have any more 3787 donors)

I'm guessing some line gets overloaded, but not sure how to check this...