A1425 820-3642

[Instafixx]

No PPBUS
No PP3v42
PPDCIn is 16.5V

Some Green on C7036
Replaced.
R7001 also had green replaced. Diode Mode reading is okay.
But Didoe mode reading on this same line at C7000 is showing different diode reading.
This is resolved by replacing C7000.
But still NO PPBUS and NO PP3V42

 

[2informaticos]

Did you check diode mode at 3V42_G3H and PPBUS_G3h?

Post U6900 voltages.
Use adjacent components as test points.

 

[Instafixx]

Diode Readings
PPBUS 0.162
PP3v42 0.335

U6900 all voltages are 0v

 

[2informaticos]

Now check Q6910 voltages.

 

[Instafixx]

DCIN_ISOL_GATE_R is 6.5V
Rest all are 16.73V

 

[2informaticos]

Check R6920 and D6905.
Possibly one leaky cap, C6990-2.

 

[Instafixx]

Diode Readings
R6920
Pin 1 2.91
Pin2 0

D6920
Pin 1 - 0
Pin 2- 0.240
Pin 3- 0.004

 

[2informaticos]

As I said, at least one of mentioned caps, or even U6990, is shorted.
R6920 is also burnt...

 

[Instafixx]

D6920 Pin 3 Short is solved by replacing a faulty cap.

Will revert after replacing R6920 and other faulty caps as mentioned

 

[Instafixx]

C6992 is already replaced to reach short at PPVIN_G3H_P3v42G3H
R6920 removed.
PPDCIN_G3H_ISOL is still 2.9 in diode mode. Is that correct ?

 

[2informaticos]

"PPDCIN_G3H_ISOL is still 2.9 in diode mode. Is that correct ?"
Why bottering with that, if already got 16.73V there???

Solder R6920 and test the board.

 

[Instafixx]

Soldered it back. Board still wont turn on

 

[2informaticos]

Do you get 3V42_G3H now?

"Soldered it back"
Same resistor?

 

[Instafixx]

No. 3v42_g3h is still low voltage.

Soldered a new resistor. Not the broken one

 

[Instafixx]

pp18v5_dcin_conn_r is 0V too.

 

[2informaticos]

You had 16.73V before.
Test with fake charger, or lab PSU.
You may have input leakage, detected by original charger.

 

[Instafixx]

PPDCIN_G3h was 16.73V.
PP18V5_DCIN_CONN_R was always 0V.

First I thought it was because of the broken R6920. But even after replacing R6920 its still the same.

 

[2informaticos]

"Now check Q6910 voltages
....................................
DCIN_ISOL_GATE_R is 6.5V
Rest all are 16.73V"
Don't you have voltage at pin 1/R6920???

 

[Instafixx]

Yes Pin 1 of R6920 is 16.73V but Pin 2 is 0V

 

[2informaticos]

Don't you think to change R6920 with correct value?