Yeah it seems I got lucky today as it's fully working right now... unfortunately I have no real idea why it decided to boot today of all days versus back when I made this post, but I'll do my best to retrace my steps for you along with my observations.
I first attempted to try alternate BIOS's from badcaps, including one an individual customised for me, alas it actually made the problem worse:
- No fan spin
- no keyboard light
- brief light on power button, then off
- no backlight
After a couple attempts I simply reverted to my OG BIOS,...
left_cap
Member
Last Activity: 03-29-2025, 02:26 PM
Joined: 01-01-2025
Location: Toronto/ON
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I tried running this bios once padded but it won't even attempt to turn on...Leave a comment:
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Its tragic how bad windows search became over the years, like seriously Microsoft if I wanted a result from the web I'd use my browser. Worse yet it's powered by bing! 🤢...Leave a comment:
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I had a look at the schematic and board view:
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3540542}[/ATTACH]
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3540543}[/ATTACH]
From the above I don't believe ​"BU31" connects to any test pads on the mobo besides a pad directly under the BGA, and no reference to dram reset on...Leave a comment:
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It seems it's a FX490 NM-B861, Rev 1.0,date code 2019/03/28, Vendor: UMT...Leave a comment:
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PF-1YJ74S...Leave a comment:
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The device as per my [URL="https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-laptops-tablets-and-mobile-devices/3539777-lenovo-thinkpad-x1-yoga-4th-gen-20qf-ct01ww-fan-spin-but-no-post"]first post[/URL] powers on but does not POST, BIOS could be corrupt but I'm not sure how to verify that. Original BIOS/TB Firmware attachedThe device as per my [URL="https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-laptops-tablets-and-mobile-devices/3539777-lenovo-thinkpad-x1-yoga-4th-gen-20qf-ct01ww-fan-spin-but-no-post"]first...Leave a comment:
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Lenovo Thinkpad X1 Yoga 4th Gen (20QF-CT01WW) Fan Spin but No POST
Hey Folks,
I have a 4th gen X1 yoga I'm trying to repair, current state:
- Laptop charges battery fine and or no obvious power circuit faults
- When power button is pressed, keyboard briefly lights up, power button lights up and stays on, brief fan spin
- No display or back light, does not respond to external display, and caps lock does not work (no response to keyboard presses)
- If device is left on the CPU fan will ramp up/down as the CPU warms up
To me it seems the device fails to POST, I have tried flashing a 20QF bios from the bios...
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