[SOLVED]820-3787 Dead DC-IN Board + F7005 blown. Now quarter fan spinning

[bjf]

Any shorts to ground? Vcore, other lines? If no short, is vcore present during the cycle?

 

[phuketmymac]

No short that I could find at least.
Vcore is present at 1.8V when it turns on.

The weird thing is how quick it would turn off and back on again.

Now, not to forget this is happening with a DC power supply.
On a 85W magsafe, I get a quick green light and then off so there might be some short protection happening.

So far U7000, U7001 and U7100 have been replaced but no go.

I am assuming that I only have to check the S0 rails since Vcore is coming up but I might be wrong? right?

 

[dukefawks]

PPBUS voltage?

 

[phuketmymac]

12.67V

I see dropping to 10V using the multimeter and back to 12.67V

 

[phuketmymac]

Replaced Q7010 and D7010 and it did fix this issue.
Fixed.

 

[phuketmymac]

Well I am not out of the woods yet.
Screen is now flickering. It seems to happen when the computer is switching graphics from Intel IRIS to Nvidia GPU.
Once connected to an external monitor, it is stabilized.

Could the Mux chip be dead in your opinion?

 

[dukefawks]

Possible to make a video of that? Flickering on Intel video is unfortunately often a bad CPU.

 

[phuketmymac]

Here is the video: https://youtu.be/ZNsPcd9ihkg

I also did run ASD and it has reported an error on sensor IO5R

 

[dukefawks]

Probably corroded trace to U5420. Maybe that will fix the flicker issue, but honestly I would not worry about a small flicker like that only when switching GPU.

 

[phuketmymac]

Well I did replace U5420 + check rework all the resistors R831X.
Funnily it did work for a while and once the customer came to pick up the laptop it happened again... some kind magnetism

Anyway, happy customer who didn't pay for the repair ;-)