Chromebook USB-C no longer recognized USB devices after shorting

[theflyingsquirrel]

@ ~20v, the power delivery section / controller / firmware is working on your logic board. Do not disturb these sections. Next, continue to check if the same ~20v travels onto the battery charger IC power path.

Share again the markings on your battery pack. What is the voltage marking on the official battery pack?

On power delivery communication, only the CCx (ie. CC1, CC2) pins are active for the 1-wire BMC communication between the PD controller and the PD external power source / adapter. Respectively, the data lines on the same USB connector could be disconnected and PD can still function.

I took some photo of the reworked area. I think the chip is soldered ok. I added picture of the battery pack too.
Also I used the USBC tester with usb hub, external power source and USB stick and it seems that there is a -2.19V on data- line.
I checked with another same model with the same setup and the data- line briefly show 0.02V and then become 0V. So the 2.19V may be a sign of something wrong.

I measured the battery connector voltage and it is 8.59V when the power adapter is connected.
I am ordering an usbc expansion board in order to further test the USBC port pins.
I used the tester with power adapter on another same model chromebook and the voltage is around the same. I think the charging part is working ok. But the USBC memory stick just do not work.

[mon2]

What is the full part # of this unit? Are there schematics available in the schematics forum?

[theflyingsquirrel]

What is the full part # of this unit? Are there schematics available in the schematics forum?

It is a Samsung Chromebook Pro XE510C24.
I can't find the schematic and a quick search in the schematic forum show no result.
You know if there is any other place I can search?

[theflyingsquirrel]

@ ~20v, the power delivery section / controller / firmware is working on your logic board. Do not disturb these sections. Next, continue to check if the same ~20v travels onto the battery charger IC power path.

Share again the markings on your battery pack. What is the voltage marking on the official battery pack?

On power delivery communication, only the CCx (ie. CC1, CC2) pins are active for the 1-wire BMC communication between the PD controller and the PD external power source / adapter. Respectively, the data lines on the same USB connector could be disconnected and PD can still function.

Ok. The USBC expansion board finally arrived!
I measured the value between 3 stages with it on 2 computers. One known good one and the defective one and get the values in the table in the attachment.
State 1: No connection
State 2: Connected with USB stick
State 3: Connected to charger

It seems that the values are mostly the same except that when connected to USB stick, there is 0 voltage on D+ pin and Vcc pin.
One of the CC pin has 5.1V so it should be calling for voltage on Vcc to power the USB stick but none showed up.
I am thinking may be the pull up circuit is not working?

[mon2]

To me, the CCx pins should never be as high as 5v1. From my understanding, this voltage swing is defined by a LDO onboard the PD controller chip (ie. study the CD3215 for example). Often this rail is 1v1 range. Study the details of the PD controller onboard which may be defective.

[theflyingsquirrel]

To me, the CCx pins should never be as high as 5v1. From my understanding, this voltage swing is defined by a LDO onboard the PD controller chip (ie. study the CD3215 for example). Often this rail is 1v1 range. Study the details of the PD controller onboard which may be defective.

I am trying to read and understand the USB-C standard and it seems that cc is the same pin as Vconn that can supply 5V 1W.
Perhaps the transistor switch that connect to Vconn is blown closed. I really wish I have a schematic.

[mon2]

There are legacy USB C adapters where the output voltage is just fixed @ 5v. Then the shared slide applies.

However, if you have a PD (power delivery) capable power adapter then the power adapter is intelligent and offers communication over the CC1 / CC2 lines (1-wire BMC interface) - the one connection is present on one side of the USB-C blade and another on the other side so you can support 180 degrees of cable flipping and still function.

The PD controller on your logic board will extract the database of PD contracts out of the intelligent power adapter and then select the best pair (voltage / current) to power the board.

Suggest to sign up (if not done already) with Mobile Sentrix and purchase their Qianli Tail tester tool. It is a very handy tool that can be used to debug USB-C and also lightning based products. The cost is ~$23 CAD + shipping.

https://www.mobilesentrix.ca/ibridge...-tester-qianli

SKU # 107182137211

Their search engine on their website is just horrible. A royal pain to find the above tool. Review the assorted internet videos for this device. The tool will help on this and future cases. With this tool, you can review the PD contract being selected (or not).

[theflyingsquirrel]

There are legacy USB C adapters where the output voltage is just fixed @ 5v. Then the shared slide applies.

However, if you have a PD (power delivery) capable power adapter then the power adapter is intelligent and offers communication over the CC1 / CC2 lines (1-wire BMC interface) - the one connection is present on one side of the USB-C blade and another on the other side so you can support 180 degrees of cable flipping and still function.

The PD controller on your logic board will extract the database of PD contracts out of the intelligent power adapter and then select the best pair (voltage / current) to power the board.

Suggest to sign up (if not done already) with Mobile Sentrix and purchase their Qianli Tail tester tool. It is a very handy tool that can be used to debug USB-C and also lightning based products. The cost is ~$23 CAD + shipping.

https://www.mobilesentrix.ca/ibridge...-tester-qianli

SKU # 107182137211

Their search engine on their website is just horrible. A royal pain to find the above tool. Review the assorted internet videos for this device. The tool will help on this and future cases. With this tool, you can review the PD contract being selected (or not).

Thanks. I will definitely get that tools.
I did some micro inspection around the transistors that is relating to the cc1 and cc2 pin. I found one component that looks like it is melted as shown in the attached pictures. It is a black piece that marked M. I took a photo of another board of the same model to make out what this smd should look like. I don't even know what is it.

[mon2]

It is probably a 2 pin TVS ESD diode that is present to shunt any transient on this line. Remove all power. Meter in resistance mode. Measure the resistance to ground of this trace that is mating to this part. What is the resistance in ohms? Suggest to flux and remove this part off the board then test the resistance again to ground of this trace but without this part onboard.

[theflyingsquirrel]

It is probably a 2 pin TVS ESD diode that is present to shunt any transient on this line. Remove all power. Meter in resistance mode. Measure the resistance to ground of this trace that is mating to this part. What is the resistance in ohms? Suggest to flux and remove this part off the board then test the resistance again to ground of this trace but without this part onboard.

I removed that component. One side is 1.3Ohm to ground. The other side should no reading.
I took another same component from the other board and replaced it.
Interestingly, when I plug in charger, the voltage is now 5V instead of 19V.
When I plug in USB stick, the vcc is still 0V.

[mon2]

The side with 1R3 to ground is most likely the ground PCB trace. The other side with no reading is the CCx pin and is now without a short. Confirm the trace is mating to the CCx pin on the connector.

The power on default of all power delivery (PD) controllers will be 5v. This voltage is presence in the absence of a full communication handshake with the power adapter. Once the communication proceeds, the CCx pin will request a full list of power delivery contracts from the power adapter. From this list, the PD controller will select the best pair which will be 20v & xx A for current to power and charge the laptop.

In order for a voltage of 5v to be present on a USB device like the stick, the battery must be working and be with enough charge to power such devices or the power supply adapter must be able to power the board -> allow for the PD controller with firmware to power this sink device.

[theflyingsquirrel]

The side with 1R3 to ground is most likely the ground PCB trace. The other side with no reading is the CCx pin and is now without a short. Confirm the trace is mating to the CCx pin on the connector.

The power on default of all power delivery (PD) controllers will be 5v. This voltage is presence in the absence of a full communication handshake with the power adapter. Once the communication proceeds, the CCx pin will request a full list of power delivery contracts from the power adapter. From this list, the PD controller will select the best pair which will be 20v & xx A for current to power and charge the laptop.

In order for a voltage of 5v to be present on a USB device like the stick, the battery must be working and be with enough charge to power such devices or the power supply adapter must be able to power the board -> allow for the PD controller with firmware to power this sink device.

It is still not working.
I measured the TVS ESD and you are correct. One side is connected to ground and the other side is to the CC pin.
I checked the schematic from other laptop with USBC and I found something similar to AP21510FM that has 6 pin that is directly connected to the TVS ESD. There are 2 of those chips. I think it is for CC1 and CC2.
I measured the resistance between the IN and OUT pin and one chip has only 1.7Ohm while the other chip has 4.7k Ohm.
I checked these are USB switches. These 2 chips are problem damaged as well. I will need to replace them and see what happen.

[mon2]

What are the markings on these USB switches?

[theflyingsquirrel]

What are the markings on these USB switches?

It looks like GP7oE. I googled it and there is no result.

[mon2]

Pour some ipa onto the part to enhance the markings and take a picture and post it here. The markings are a mix of the part number and the mfr date code.

[theflyingsquirrel]

Pour some ipa onto the part to enhance the markings and take a picture and post it here. The markings are a mix of the part number and the mfr date code.

It seems like it is GP 7cE on a closer look. I added the pin out and relating circuit from the schematic of another computer I found.

[mon2]

Excellent find. The part is indeed AP21510FM with the 'GP' SMD code from Diodes Inc.

If you have the low resistance between in/out pins on this load switch then the load switch is defective and needs to be replaced. Flux and remove this part. Then test the resistance to ground of the in/out pins again to confirm there are no other defective parts in this Vbus path to the USB connector.

[theflyingsquirrel]

Excellent find. The part is indeed AP21510FM with the 'GP' SMD code from Diodes Inc.

If you have the low resistance between in/out pins on this load switch then the load switch is defective and needs to be replaced. Flux and remove this part. Then test the resistance to ground of the in/out pins again to confirm there are no other defective parts in this Vbus path to the USB connector.

I removed the 2 parts for the right side port and measured the resistance to ground and it all looks good.
I took scrap part from another board and put in. Measuring again and nothing is shorting to ground.
Unfortunately, it still behave the same as before replacing those parts. Further investigation is needed.

On a side note, I measured the voltage on the left side UCBC port and the cc1 pin at A5 is getting 1.2V while the cc2 at B8 is not getting any voltage. Something from the other port is probably has another defective component. I measured the GP on the left side port and it seems normal.

[mon2]

CC2 will show a voltage once you flip the USB-C cable by 180 degrees. That is,

CC1 is the active communication line but CC2 will be inactive and
CC2 is the active communication line but CC1 will be inactive once the USB-C cable is flipped by 180 degrees.

Only one side of the USB-C blade is active at any one time.

[theflyingsquirrel]

CC2 will show a voltage once you flip the USB-C cable by 180 degrees. That is,

CC1 is the active communication line but CC2 will be inactive and
CC2 is the active communication line but CC1 will be inactive once the USB-C cable is flipped by 180 degrees.

Only one side of the USB-C blade is active at any one time.

Ok. I think I should check the resistance from the circuit along cc line to ground again. I must have missed something.