Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

[speggio91]

Hello all, sorry for the double post (i've posted this question on another thread of schematic request).

i'm working on this board that doesn't have any power at all, the usb-c ammeter stay off and the thermal camera doesn't show anything heating up.
I have no experience with usb-c powered boards, but I know there's a thunderbolt chip negotiating with the power supply and the power management chip.
Could it be the intel jhl8040r thunderbolt controller (U7101) to be dead?
Probing the caps around it i didn't find anything shorted.
Can someone give me some hint to start hunting for the probable issue with this board please?
I know I didn't give many informations but judging by the fact that neither the usb-c meter is turning on made me thing about the thunderbolt chip.

Thanks to anyone that will contribute

[mon2]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

Confirm that the type c power adapter is working and test your type c meter to confirm again that both are working as a team.

Do you see the power up default of 5 volts on your type c meter?

Then insert this combination into your logic board. If the meter goes dark, then you have a short condition on the logic board.

Power cycle everything that is connected and flip the USB C connector by 180 degrees. This will test the other side of the type c interconnect.

What are the results after flipping the power connector head?

[speggio91]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

Thank you very much!

Both usb-c power supply and meter are working well, I've tested them on other usb-c powered devices such as Macbook air, hp laptops and they delivered the power needed by those devices.

The default behaviour of the Usb-c power supply I have is that even after I plugged it into the power outlet and connected the ammeter, it won't deliver any voltages until I have plugged it into the device. So in every case, the usb-c meter won't be powered on at all until it will be connected to the devices usb-c port.

In the case of this Dell laptop, the screen of the meter stay off and it won't show any voltages, neither 5 volts.
I know that the ammeter is not powered on because it's not emitting any beeping sound that is typically heard when the power start flowing through it, into the usb-c laptop.

I've checked also that the power supply is capable of delivering the requested voltage and it is, it matches the 20V 3.25A of power needed by that dell. It's not the original power brick that came with the laptop but i will probably ask the owner to give it to me just to be sure it's not just a power adapter issue that need a specific chip to negotiate the voltage to the laptop board.

I've removed the motherboard from the case and flipped the usb-c connector with no changes on the final result, still no sign of life or power.

[mon2]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

Remove all power. Meter in DIODE mode.

Red meter probe, yes red to ground.

Black meter probe to the CC1 line of the TPS power delivery chip.

What is the reading?

Repeat for the CC2 line.

These 2 lines are used to detect if the power adapter is mated or not and are used to extract and negotiate the power delivery contracts from the adapter.

[speggio91]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

I've probed on diode mode pins 46 and 44 of U7202 and..
pin 46 show 0.00V, pin 44 0.025V

I also probed some other pins (1, 9, 11, 45) and all of them measure 0.00V

Does it mean the PD chip is dead?

I've measured also ED7301 until ED7308 and all of them are above 0.500V in diode mode.
I wasn't able to find on the board C7213 and C7208.

What should be the next step? Power injection in one of the shorted pins of the PD chip to see what does heat up or remove the chip to measure those pins again?

Thanks

[mon2]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

ED7307 and ED7308 should report the same readings as what you measure at the connector pins.

Can you confirm the readings again?

The diode readings do not show a fault but the connector readings are common to a short.

[speggio91]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

I confirm you that the readings on ED7307 and ED7308 are 0.00V and 0.025V, earlier I wasn't able to find those components on the board and I assumed that they were located right next to U7020 but intead they were in another position. So the reading I reported earlier weren't the right ones.

[mon2]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

Ok - with care - remove ED7307 and ED7308 off the logic board. Flux and low air pressure.

It is possible that an ESD transient event has killed these ESD diodes on the CCx lines. By removing these parts, you can check again if the diode readings improve or not.

If the diode readings remain the same, then will conclude that the power delivery controller is defective.

Keep these diodes in case they are still ok.

[speggio91]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

Removing ED7307 and 7308 didn't change the reading, but removing C7208 (it's in parallel with ED7308) the reading on pin 46 changed to 0.020V.

During the resoldering process of the diodes unfortunately ED7308 slipped away from the tweezers and cannot be found again.
The situation now is, both ED7307 and C7213 are soldered back and pin #44 still reads 0.025V.
If i solder back C7208 the reading of pin #46 goes to 0.00V.
Measuring C7208 in resistance mode, give me OL. With the capacitance function the value is 0.419 nF.

Are those diodes meant to protect the PMC from ESD discharges?

[speggio91]

Re: Dell Inspiron 7306 Hellcat 13 TGL MB - No Power

I desoldered U7202 and took some measurements.
The pin #8 that should be the one that generate 3.3V on S5 state has 3.5 Ohm to ground resistance which it seems quite low, isn't it?
I've tried to inject 3V and immediately PU5302 get hot.
Measuring PIN #6 (that is part of the 5V_S5 line) of PU5302 show me a resistance to ground even lower, 2ohms.
Both PC5311 and PR5301 are fine, no short to ground was detected.
Do you think that those 2 lines 3.3V S5 and 5V S5 are really shorted to ground?
Should I try to replace U7202 ignoring those resistance values?
I'm afraid the the issue is more extended than what it seemed..