820-00840 Stuck on 5V

[brunomotter]

Hello. Got an 820-00840 that was negotiating 19V with charger but drawing just 0.02A. During measuring I slipped the probe of the multimeter and burned the PP3V3_G3H_VR circuitry and no 19V anymore obviously. I managed to fix the 3V3 circuit and board is giving 3.3V again but still no 19V. On USBXCA I get steady 5.1V, 0.03A. On USBCXB I also get 5.1V 0.03 amps but it keeps resetting my charger. I thought maybe U3200 was dead and replaced it, still same behavior. Verified all caps around U3200 and U3100 and there are no shorts. Any ideas?

 

[2informaticos]

Compare diode mode readings on LDO rails of both CD3215 chips.
When you slipped the probe multimeter, did you accidentally inject high voltage into 3V3_G3H rail?

 

[brunomotter]

Probably. It’s been days ago I did it. I was waiting for stencil to arrive to replace CD3215 from donor board as I did have good CD3215 and did not have the stencil for it. I’ll diode mode and post back

 

[brunomotter]

PP3V3_UPC_XA_LDO - 0.172
PP3V3_UPC_XB_LDO - 0.475(strange!)

this is the only LDO line that is giving inconsistency between U3100 and U3200

 

[2informaticos]

Change U3100, as first suspect.
If still the same, follow that power rail; be aware, it changes the name few times.

 

[brunomotter]

Replaced U3100 and got 19V back, but 0 amps drawing. What's next?

 

[brunomotter]

PPBUS_G3H stable at 13v. Still no current draw

 

[2informaticos]

Do you get 3V3_S5/SUS?

 

[brunomotter]

No 3V3_S5... 0V there!

 

[2informaticos]

Check basic voltages and signals for U7800 (7 OF 10), page 60.

 

[brunomotter]

Hello. What exactly would be those "basic signals"?

 

[2informaticos]

The very basic ones, to wake up the PMIC; VINLDO3, LDO3V/5V, VREF1V25.
Also check SHUTDOWN*, ACOK and V3P3A_RTC.

 

[brunomotter]

VINLDO3 = 13V
PP3V3_LDO3V = 3.3V
PP5V_LDO5V - 5V
VREF1V25 - 1.248V
PMIC_SHUTDOWN_L = 3.345V
SMC_PM_G2_EN = 3.41V
PP3V1_RTC = 3.088V

As all signals appear to be OK, I assumed PMIC was bad and replaced it from a donor board, but still same! There's a chance the other board got a bad PMIC too though...

 

[2informaticos]

Post U7890 voltages.

 

[brunomotter]

PIN 1 - goes from 0V up to 1.5V, dies and goes up to 1.5V again in loop
PIN 2 - 0V
PIN 3 - 0V
PIN 4 - 0V
PIN 6 - 3.3V

 

[2informaticos]

No pulse at all at PMIC_EN_P3V3S5 at all?
Be sure R7883 is good.

 

[brunomotter]

I think it's giving a pulse yes, but my multimeter is not so fast to catch it properly. I notice a little variation on voltage though... R7883 is good.

 

[2informaticos]

You should note the pulse at pin 4/U7890 too.
An o-scope can help, it catches the peak of any fast pulse.

 

[brunomotter]

I'm measuring on Pin 1 of R7890 because U7890 is BGA. It seems to pulse. I leave the multimeter probe on R7890 with charger disconnected and it stays steady on 0.00V. When I plug in the charger and it negotiates 20V with the board I get a peak of around 150mV for a fraction of second and it comes back to 0.00V again on my multimeter. I do not have oscilloscope here, so cannot measure it precisely. But it seems to pulse.

 

[2informaticos]

Check for pulse at R7662.
If you are not sure, remove it and check at its pad 1.