w550s/t550 LCD screen replacement - brightness set at max.

Discussion in 'Lenovo' started by giggidy, Apr 5, 2015.

  1. damnation333

    damnation333 Notebook Enthusiast

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    Have a look here: https://communities.intel.com/thread/25904?start=165&tstart=0 (see the lower post by Bryce). I have followed that thread since I got my t450. Just checked now and found they put out that new driver 2 weeks ago. Can't wait to try that tonight.
     
  2. Spearoid

    Spearoid Newbie

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    That's pretty nice to see...I've installed this latest driver just now...the exe wouldn't take on my T450s....I had to extract the contents and point device manager to the actual driver file to update the driver.

    Not exactly sure how to take advantage of this potential EDID override allowance in the driver though. The MSDN article is pretty general.
     
  3. l_i_l

    l_i_l Newbie

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    Hey, I just got a used Thinkpad T450s, and the previous owner replaced the stock screen with an LG FHD screen, and I'm getting exactly the same problems as described here. I've read through the thread, and it seems there are two ways of correcting this that were found successful: 1) changing the BIOS whitelist to include the current screen EDID; 2) changing the actual screen EDID to one of the whitelisted values. I'd preferably avoid either of the two options, because 1) it makes future BIOS updates (if any) harder than necessary, and 2) because I don't have the necessary equipment (I think I need a BIOS programmer or Arduino or something, please correct me if I'm wrong).

    It also seems that Intel's latest driver (released about a month ago) for the HD 5500 supposedly allows for overriding the EDID. As previous posters have noted, this gives me a third option, that appears to be still untested, as I wasn't able to find any reports on it.

    I have managed to get one of the whitelisted EDIDs in the registry, generating a .inf file using MonInfo, and then installing the driver using Device Manager. Upon inspection of the registry entries, everything appears to be ok, and the current EDID value matches the desired whitelisted one. However, the problem is not solved at all, I still have no control of the brightness whatsoever. Does anyone have any suggestions?

    If this doesn't work, is flashing the BIOS the only option?
     
    Last edited: May 3, 2017
  4. miomi

    miomi Newbie

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    @l_i_l
    If your new panel's EEPROM is not write protected, you can just rewrite the new panel EDID with the original panel EDID. No need hardware equipment, it can be done just with a software like edid-rw.

    I had tried the override inf and registry method, including installing latest intel graphic driver from intel, but no avail.

    ---

    Eventually I managed to solve the issue by rewriting the panel's EDID (luckily my panel's eeprom is not write protected).

    Here is the how-to if anyone interested:

    1) You will need linux OS (ubuntu or linux mint for example) to run the software. You can also use bootable linux usb stick.

    2) Follow the "Installation" part from https://github.com/bulletmark/edid-rw

    3) You would need to find out the panel bus number first. You can do this with command:

    Code:
    $ sudo ./edid-rw 0 | edid-decode
    where the number 0 is the bus number you want to check.

    If you got result like this:

    Code:
    Extracted contents:
    header:          00 ff ff ff ff ff ff 00
    serial number:   30 e4 45 03 00 00 00 00 00 15
    version:         01 04
    basic params:    90 16 0e 78 02
    chroma info:     e8 87 96 5a 55 95 28 22 51 55
    established:     00 00 00
    standard:        01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
    descriptor 1:    4c 1d 00 ec 50 20 18 30 40 30 57 00 d9 88 00 00 00 1b
    descriptor 2:    16 12 00 80 50 20 16 30 30 20 47 00 d9 88 00 00 00 1b
    descriptor 3:    00 00 00 fe 00 43 33 47 52 4e 80 31 30 31 57 58 31 0a
    descriptor 4:    00 00 00 00 00 00 41 32 a8 00 00 00 00 01 01 0a 20 20
    extensions:      00
    checksum:        9a
    
    Manufacturer: LGD Model 345 Serial Number 0
    Made week 0 of 2011
    EDID version: 1.4
    ...
    then you got the panel bus number. If not, retry by increasing the bus number until you got the number:

    Code:
    $ sudo ./edid-rw 1 | edid-decode
    $ sudo ./edid-rw 2 | edid-decode
    $ sudo ./edid-rw 3 | edid-decode
    ...
    In my T450s, the display bus number is 4 (it might vary between machine)

    Note: finding correct bus number is very important. Writing EDID to wrong bus number could destroy other connected hardware on your laptop.

    4) Next we will need to dump the original panel EDID first, so with your original panel still installed, run:

    Code:
    sudo ./edid-rw 4 >original_edid.bin
    (where 4 is the bus number you find from step 3)

    Save that original_edid.bin somewhere.

    5) Shut down the laptop and replace the screen with your new panel. Careful that before swapping the panel, make sure you have disabled the internal battery from bios. For more details about replacing panel, you could read the HMM pdf or watch the service video on lenovo site.

    6) Although it's not necessary, you can repeat the step 3 again to find the display bus number to be safe. You might want to dump the new panel's EDID too for backup (see step 4).

    7) When you're ready, run:

    Code:
    $ sudo ./edid-rw -w 4 <original_edid.bin
    to rewrite the new panel's EDID with original panel's EDID (original_edid.bin) to display bus 4 (again, double check your bus number before running the command!)

    8) Run
    Code:
    $ sudo ./edid-rw 4 | edid-decode
    to check if the EDID is successfully written. If you don't see any change on the EDID data, then it means your new panel's eeprom is write-protected.
     
  5. drrossum

    drrossum Notebook Enthusiast

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    Good news that you managed to update the EDID.

    I thought EDID write was prevented in the Intel graphics hardware, and that even if you have a dedicated GPU the display is still wired through the Intel graphics chip preventing EDID writes. Did you do the programming on your T450s? That would falsify the theory...
     
  6. miomi

    miomi Newbie

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    The EDID write is done directly to the panel's EEPROM, it's nothing to do with intel graphics chip, it's the panel. As I mentioned before, there is no hardware equipment involved in this case. But if your panel's eeprom is write-protected, then you would need to do the hardware way (using arduino, bus pirate, soldering, or such) to flash the eeprom. Like this for example.
     
    Last edited: Jul 17, 2017 at 11:42 AM
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