wangbreeze
Member
Last Activity: 03-26-2025, 09:23 PM
Joined: 01-06-2024
Location: Houston, Texas
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I would try another USB port or add external power supply to the programmer. I read it could be due to usb not providing enough current. Worth trying.... -
I think the chip is locked sometimes. In this case, you cannot read. You would need to erase and write the EC file extracted from Lenovo BIOS update package....Leave a comment:
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A quick follow up to this issue. Turned out to be the RT809F usb driver issue... Didn't know how the driver got corrupted.....Leave a comment:
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Turned out to be the programmer issue. The RT809F I have worked on the first machine but stopped working on the second (showing 0xCDCDCDCD chip id and reading garbage). I used another rt809h and everything works now....Leave a comment:
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did you update the product brand to thinkpad T**?...Leave a comment:
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Sharing my experience. I have two t490 that need svp removal. I have the rt809f programmer.
the first one did not give me problems. Read erase write and svp is gone.
however, the second one I cannot even recognize the mec chip. The programmer reported 0xCDCDCDCD as the mec chip id. This is the same as if the chip is disconnected from the programmer (i actually tried it with out any pins attached to the programmer, it also reported this chip id).
I wonder what could be the cause of this discrepancy in the chips response. The one without problem has it’s...Leave a comment:
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well. I worked on another t490 today and had this exact issue. The only difference I can see between this new one and the one I worked on two days ago was the bios version (note that they are both t490). I wonder if you were able to resolve the issue. Thanks....Leave a comment:
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Reflashing BIOS obtained from Lenovo website resolved the issue. And the board serial number (B0) can be found from a sticker on the motherboard. It is much longer than the 11 character long serial number found from BIOS information screen but that’s what the Lenovo maintenance utility takes....Leave a comment:
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Thanks for the tutorial. I have successfully removed the password. However, I cannot seem to modify the settings such as setting a new SVP password. It shows error “write protected”. Anyone has similar issues? Thanks....Leave a comment:
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I want to put a closure to this post. I discovered water damage in the area of pq14 mosfet. No wonder why connecting the fan has an impact. I cleaned it up and everything started to work as intended....Leave a comment:
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Thanks for the work and sharing. If I read it correctly, we can add another 10k resistor to enable JTAG? Thought it’s easier to add and remove than to move the small resistor around. Thank you.Leave a comment:
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A little more discovery. Disconnecting fan seems to make the power rails return. Problem on the VCC5M rail?Leave a comment:
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ok. scratch those measurement I posted yesterday. I took a closer look at the schematics and found traces of hidden drain/sources into the PU101 chip. I've take these measurement. Any inputs will be much appreciated! Thanks.
MOSFET measurement:
PQ101
High side:
gate(1) - drain(2): 542k
gate(1) - source(7): 125k
drain(2) - source(7): 317k
Low side:
gate(6) - drain(7): 550k
gate(6) - source(3,4,5) - 198k
drain(7) - source(3,4,5) - >~300k
PQ102:
High side:
gate(1) - drain(2,3,4,10): out of range...Leave a comment:
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What I don't understand is VSYS15 has about 2V even if VINT20 is 0.001V. Isn't VSYS15 generated from VINT20? Does it mean a short is present in VINT20 circuit and pulls the voltage down? Thanks.Leave a comment:
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Thank you. It's really hard to get a good probe of the mosfet. Here's the value:
pq101
source to drain: start at really low <10 k ohm and gradually increase.
5 and 6-8 pin: 140k ohms, steady
1 and 2-4 pin: >100k ohms and rising
pq102
source to drain: start at really low < 10k ohm and gradually increase
too small to probe the rest. I’m reading the source to drain from the nearby test points.
I'm also reading more about these dual mosfet and I think I did it incorrectly. They can't be measured in circuit, can they?...Leave a comment:
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Thank you and sorry about that.
it measured 695k ohms....Leave a comment:
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T480s random shutoff and then completely dead
Hello Gurus,
I got a ThinkPad T480s. It was running fine but suddenly started random shut down. When it turned off, I had to push the reset pin to bring it back to life. But it got aggressively worse and became completely dead. No charging light, no life.
I did some initial diagnostics with just the board (no battery, nothing attached, and no CMOS battery as well)
Initial testing of the coil resistance seems to indicate no dead short. The only low resistance I measured was at PL701. It reads 38 ohms.
charger gave - 20V - ok
U101B
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Hello and happy new year.
I'm in my 30s and started to learn to repair electronics. Nice to meet you all.Leave a comment:
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