Chromebook USB-C no longer recognized USB devices after shorting

[mon2]

PI3USB30532ZLE is a MUX (multiplexer) that will steer the full USB connections to either target A or target B, based on the select pin. Suggest to download the datasheet for this component. Then remove all power, meter in diode mode.

Red meter probe to ground. Black meter probe to the pin to test. Test each pin of this MUX to confirm that the pin is not shorted (ie. there will be a low voltage measurement in DIODE mode if shorted) and also not 'open / floating' = OL on the meter during the same method of testing. Only wanting to confirm this MUX is soldered in properly. Otherwise, the USB connections from the physical connector are not reaching the logic board.

[theflyingsquirrel]

PI3USB30532ZLE is a MUX (multiplexer) that will steer the full USB connections to either target A or target B, based on the select pin. Suggest to download the datasheet for this component. Then remove all power, meter in diode mode.

Red meter probe to ground. Black meter probe to the pin to test. Test each pin of this MUX to confirm that the pin is not shorted (ie. there will be a low voltage measurement in DIODE mode if shorted) and also not 'open / floating' = OL on the meter during the same method of testing. Only wanting to confirm this MUX is soldered in properly. Otherwise, the USB connections from the physical connector are not reaching the logic board.

Ok, will do.
Low voltage as of below 0.2V? So if I get OL, it means the pin was not solder properly?

[mon2]

Correct. Low voltage would be something even lower and close to 0v. This will imply a shorted pin inside the device under test.

[theflyingsquirrel]

PI3USB30532ZLE is a MUX (multiplexer) that will steer the full USB connections to either target A or target B, based on the select pin. Suggest to download the datasheet for this component. Then remove all power, meter in diode mode.

Red meter probe to ground. Black meter probe to the pin to test. Test each pin of this MUX to confirm that the pin is not shorted (ie. there will be a low voltage measurement in DIODE mode if shorted) and also not 'open / floating' = OL on the meter during the same method of testing. Only wanting to confirm this MUX is soldered in properly. Otherwise, the USB connections from the physical connector are not reaching the logic board.

I measured the chip PI3USB30532ZLE and got lots of OL. I think it is the flux. So I removed the chip and measure on the PCB and the chip separately. The result is in the attached picture.
I removed the STM32F chip at the same time. So the measurement is taken with both chips off the PCB.
When you combine the 2 readings, it is suppose to get AD pin short, and RX2, TX2, TX1, RX1 at OL.
Is that something to be expected? Is the CONFO/A1 pin abnormal shorting to ground on the PCB?
It seems like CONF0 and CONF1 together switch between the 3 modes. So may be it is normal.

[theflyingsquirrel]

Ok I measured again after installing the chip, the result was not as expected.
One of the VCC measured 0V while the other VCC has a number.
I would think all the Vcc pins are connected, but it seems that it is not. I wonder if it is shorted to ground when I solder it on?

Update: I measured it again and it shows a value on that pin. I must have measured it wrong last time.
Everything seems normal from the reading.

[theflyingsquirrel]

I installed the STM32 and measured the pins too.
There are a few pins that are 0V but no OL.

[theflyingsquirrel]

I am suspecting there is a TVS diode connected to VBUS pin and it is also damaged. I will need to do a grid search to see if I can find this diode if it exist.

[theflyingsquirrel]

I finally have it figured out!
I traced the VBUS line from the USBC port and looking at the schematic from another laptop, I found the USB PD and Type-C current-limited power switch X5PT4 from the picture which is similar to NX20P5090UK from the schematic.
The V out pin from this chip is directly connected to the VBUS pin on USBC port.
This is a bga chip so I had to remove it in order to get access to the pin. With the USB stick inserted, I measured the Vin pin and 5V is present. I then measured the EN pin and it is 3.3V. This chip is active high so that means the gate is closed and Vout should have 5V. But so far I got 0V so this chip must have been fried.
I took the same chip from a scrap board and reballed it. It is a bit challenging since the grids are small, but I eventually got it done. After replacing the chip, with the USB stick plugged in, I measured VCC pin at 5V!
I then booted up the machine properly and it can finally detect the USB stick!
I then test the PD charger and VCC charges at 20V instead of getting stuck at 5V like before. I think this USBC port is fixed.
However, when I test the other port, the Vcc is still at 0V. I think the same chip from the other side is also fried. But now I know what to do!

So to sum it up, so far, I replaced:
- USBC port
- the 2 MOSFET chips for both CC line
- the 2 TVS diode for both CC line
- STM32 USBC controller chip
- PI3U chip
- USB PD and Type-C current-limited power switch X5PT4

And that is for one USBC port. The other side still get Vcc at 0V with USB stick plugged in.

Thanks mon2 for all your help. Without you, I do not even have any idea of where to start. You gave me method to test and debug the circuit and direction of where to look.

[mon2]

Very nicely done! Closure is always appreciated by all readers.

The current limit switch can be purchased from Digikey (or similar) here:

NX5P3290

https://www.digikey.ca/en/products/d...AzGAnABhAXQF8g
* linked the Canadian prices for this component
* +$8 for shipping to Canada but still easier to source than to reball from a donor board

Q: Are these Chromebooks not dirt cheap and under $200 new? I recall junior mentioning that he had these at his high school and they were extremely slow compared to his quadcore i7 unit. Still may be ok to keep out of the landfills.

[theflyingsquirrel]

Very nicely done! Closure is always appreciated by all readers.

The current limit switch can be purchased from Digikey (or similar) here:

NX5P3290

https://www.digikey.ca/en/products/d...AzGAnABhAXQF8g
* linked the Canadian prices for this component
* +$8 for shipping to Canada but still easier to source than to reball from a donor board

Q: Are these Chromebooks not dirt cheap and under $200 new? I recall junior mentioning that he had these at his high school and they were extremely slow compared to his quadcore i7 unit. Still may be ok to keep out of the landfills.

I was excited after the measurements so I cannot wait to test and see the result. haha.
Yes, these chromebook are dirt cheap. This model is probably around $30 to $50 USD currently.
But I will have to say Samsung Chromebook Pro is the best thickness, size and weight laptop made ever.
It is thinner and lighter than Apple Air but the resolution is at stunting 2400x1600 pixels.
Yes it has only soldered on parts like 4GB of RAM and most model has only 32GB storage, but those can be modified.
EMMC can be modified to 128GB for cheap and I can mod the ram to 16GB.
The processor is a bit lacking but it is suffice for daily task that I need to do.
This chromebook can be modified into using window 10 and I can use the SD card to load Linux to have dual boot.
It is a monster in disguise.

Besides, it is fun to troubleshoot and repair something that the repair shop will not even attempt to do.
And I actually learnt a lot from this repair! That is priceless.

[mon2]

Nice display!! Will review it. Designing a new line of products for home automation and in the market for a nice hd display. Studying the mipi dsi interface which is a bit of a guarded mystery but getting very close to start a custom pcb layout for testing.

[theflyingsquirrel]

Nice display!! Will review it. Designing a new line of products for home automation and in the market for a nice hd display. Studying the mipi dsi interface which is a bit of a guarded mystery but getting very close to start a custom pcb layout for testing.

Wow. Nice. You are great with investigating interfaces.
Does most home automation product use ESP32 nowadays?