I will try to find more information tomorrow.
Is there possible that the sequence starts from 5V? The battery is 7.84V so may be it works it way down?...
theflyingsquirrel
theflyingsquirr
Last Activity: Today, 03:41 PM
Joined: 02-21-2025
Location: Toronto
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Samsung Chromebook Pro missing 1.2V power rail and no boot
I am trying to repair my Samsung Chromebook Pro. There is no boot. Upon turning on, the screen is blank and there is no backlight. Power LED is blue. I tried refresh with power and esc refresh with power with no avail.
When I measure the 1.2V rail, it is pulsing. It will jump from 0 to 1.2V then 0 again. I replaced the 2 MOSFET and even power management IC and it is the same. Resistance from midpoint between mosfet to ground is 0.5 kOhm but it will show 250 Ohm first before jumping to 0.5 kOhm. So it feels like it was charging up some capacitor. Since MOSFET and IC was replaced, I... -
Wow. Nice. You are great with investigating interfaces.
Does most home automation product use ESP32 nowadays?...Leave a comment:
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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.
...Leave a comment:
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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...Leave a comment:
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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.Leave a comment:
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I installed the STM32 and measured the pins too.
There are a few pins that are 0V but no OL....Leave a comment:
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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....Leave a comment:
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I measured the chip [B]PI3USB30532ZLE [/B]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 norm...Leave a comment:
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Ok, will do.
Low voltage as of below 0.2V? So if I get OL, it means the pin was not solder properly?...Leave a comment:
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Ok. I think I should check the resistance from the circuit along cc line to ground again. I must have missed something....Leave a comment:
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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...Leave a comment:
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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....
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It looks like GP7oE. I googled it and there is no result....Leave a comment:
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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...Leave a comment:
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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....Leave a comment:
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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....Leave a comment:
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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....Leave a comment:
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Need Samsung Chromebook Pro XE510C24 Schematic
Hi everyone, I have a Samsung Chromebook Pro XE510C24. It has some problem with USB-C shorting. Does anyone has a schematic for the PCB of this board? -
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...Leave a comment:
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