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How to Calibrate a Kobo eReader Display

Introduction

Use this guide to calibrate a Kobo eReader E ink display. This is done by changing the VCOM number, or "common voltage" number in your Kobo eReader to match a new motherboard or new E ink screen.

This guide works with the Kobo Libra Colour and the Kobo Clara BW and Colour models.

The VCOM number is the reference voltage associated with the device's screen. In order for your screen to work properly, the stored value needs to match the VCOM number printed on the screen. You'll need to change the VCOM number if you replace the screen or the motherboard.

Changing the VCOM number is only recommended during display or motherboard repairs. If the motherboard's stored VCOM number doesn't match the VCOM number associated with the connected E-ink display, you might see ghosting or a fuzzy / unclear picture. If the VCOM numbers stay mismatched for long periods of time, this may result in permanent damage to the E-ink display.

  1. How to Calibrate a Kobo eReader Display, Check your VCOM number: step 1, image 1 of 3 How to Calibrate a Kobo eReader Display, Check your VCOM number: step 1, image 2 of 3 How to Calibrate a Kobo eReader Display, Check your VCOM number: step 1, image 3 of 3

    • Check the display cable for the three digit VCOM number.

    • For example: -2.81

    • If your screen doesn't have a printed VCOM number, scan the QR code with a dedicated QR scanner app to generate the number. Your phone's built-in camera app won't work.

    • The VCOM number registered on your tablet will be this three digit number multiplied by 1000.

    • For example: -2.81 x 1000 = -2810

    Edit

  2. How to Calibrate a Kobo eReader Display, Navigate to Device Information: step 2, image 1 of 3 How to Calibrate a Kobo eReader Display, Navigate to Device Information: step 2, image 2 of 3 How to Calibrate a Kobo eReader Display, Navigate to Device Information: step 2, image 3 of 3

    • From the home screen, select More at the bottom right corner.

    • Select Settings.

    • Select Device information.

    Edit

  4. How to Calibrate a Kobo eReader Display, Locate the stored VCOM number: step 3, image 1 of 2 How to Calibrate a Kobo eReader Display, Locate the stored VCOM number: step 3, image 2 of 2

    • Find the row titled Firmware information and select View.

    • The VCOM number will be listed on the popup. Compare it to the VCOM number for your screen.

    • If your VCOM numbers match, your screen is already calibrated—you're done! If the numbers don't match, follow the next three steps to change the VCOM number.

    Edit

  5. How to Calibrate a Kobo eReader Display, Connect your device to a computer: step 4, image 1 of 3 How to Calibrate a Kobo eReader Display, Connect your device to a computer: step 4, image 2 of 3 How to Calibrate a Kobo eReader Display, Connect your device to a computer: step 4, image 3 of 3

    • Plug your eReader into a computer.

    • You'll be prompted on the tablet that a computer is detected. Select Connect.

    • While the tablet is connected, you can't use it.

    • If you're having trouble connecting to your computer, click here for troubleshooting information.

    Edit

  6. How to Calibrate a Kobo eReader Display, Change the VCOM number: step 5, image 1 of 3 How to Calibrate a Kobo eReader Display, Change the VCOM number: step 5, image 2 of 3 How to Calibrate a Kobo eReader Display, Change the VCOM number: step 5, image 3 of 3

    • On your computer, use a text editor to create a .txt file named vcom with only the desired VCOM number (including the negative symbol and the x1000 multiplication).

    • For example, if the VCOM number on the replacement screen is -2.89, the file will say exactly -2890.

    • Find the drive called KOBOeReader and open it.

    • Move the vcom file into the drive.

    Edit

  7. How to Calibrate a Kobo eReader Display: step 6, image 1 of 2 How to Calibrate a Kobo eReader Display: step 6, image 2 of 2

    • On your computer, eject the eReader.

    • Once the device successfully ejects, you'll be prompted to update the VCOM number. Select OK to update the number and restart the eReader.

    • If you don't get prompted, repeat the previous step to ensure your file was formatted and named properly.

    • Navigate back to the Firmware information page and check if your VCOM number has updated.

    • If your VCOM number is updated, you're done! If not, double check each step in this guide to confirm the procedure was done properly.

    • The updated VCOM value might not match the number you entered to the exact digit. As long as it's close, you'll be fine!

    Edit
Conclusion

Calibration didn’t go as planned? Try some basic troubleshooting, or ask our Answers Community for help.

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Alex Diaz-Kokaisl

Member since: 01/16/22

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3 Comments

Any way of doing this on a kobo nia? I just changed my cracked screen and I don't have the vcom heading, nor do the steps work for my model.

Cheers

Mark B - Reply

I saw some posts on forums commenting that some users opened their Kobo and noticed that the VCOM indicated on the board was different from the VCOM configured in the system. My question is whether I should open my Kobo to check if my model also has a mismatched configuration. It seems that several devices are coming with them misconfigured, and here on iFixit, there is the following information: If the VCOM numbers stay mismatched for long periods of time, this may result in permanent damage to the E-ink display.

So, should I open it to check or ignore it, even though there is a possibility that my Kobo is misconfigured? Any suggestions from Kobo or iFixit regarding this?

V M - Reply

Hi, my reader's VCOM value is -1352mV and I've tried to open the back cover to check my VCOM number and found -1.36, I changed to the new value and "upload" to my reader like your procedure, but every time I reboot my device and found the value changed nothing, remains -1352mV.

I'm making sure that each step is correct. Does anyone know what's the problem?

r6b444 - Reply

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