HowTo: Dell Wyse ThinOS Downgrade from 9.0 to 8.6

If you have performed your first Dell Wyse ThinOS 9.0 tests by now, you might want to downgrade those devices back to 8.6 again. In this guide I’m showing you how.

Dell Wyse USB Imaging Tool

For this test, I initially upgraded a Dell Wyse 3040 ThinClient with ThinOS to 9.0 with the Dell Wyse Management Suite 3.0. After my tests were finished, I wanted to use 8.6 on this device again, as I use it mainly to reconstruct customer issues, and most customers still use 8.6.

Go to and download the latest Version of the Dell Wyse USB Imaging Tool, which is as of today version 3.3.0. You should also consider downloading and reading the User’s Guide.
Install the app on your Windows PC.

Next, you have to download the proper Merlin Image for your device not the raw image, in our case a Dell Wyse 3040:

Dell Wyse 3040 Firmware Download Page
Dell Wyse 3040 Firmware Download Page

Extract the ZIP files until you reach the .RSP file:


Now prepare a 2GB+ USB flash drive and format it with FAT32.

Next, start the USB Imaging Tool with Admin permissions. Select the correct USB-Drive and select Image Push mode in 64 bit. Press the + button at the bottom and select the WTOS_3040_8192_0.rsp file. Confirm your configuration and let the tool create the USB drive.

Dell Wyse USB Imaging Tool
Dell Wyse USB Imaging Tool

After the USB drive is created, eject it from Windows and plug it into your Dell Wyse 3040 with ThinOS 9.0.

Warning: Don’t use the blue front UBS 3.0 port, that didn’t work for me. Only the two back ports worked for me.

Start up the device and press F12 until you the pre-boot selection menu appears. Select the Device:

Boot selection menu
Boot selection menu

Hint: If the USB device does not appear in the boot menu, you may want to enter the BIOS settings and reset it to factory defaults.
The default BIOS password for Dell Wyse devices is: Fireport

You’ll now boot up the imaging menu and select the prepared 8.6_013 image, which will downgrade ThinOS from 9.0 to 8.6:

Dell Wyse USB Imaging Tool
Dell Wyse USB Imaging Tool

Press OK to start the process:

Start Image Pushing
Start Image Pushing

Wait until it’s finished:

Image Pushing
Image Pushing

After the process finished successful, remove the USB drive and press the restart button:

Successful Imaging
Successful Imaging

The setup will continue, finish and leave you with a Dell Wyse 3040 ThinOS version 8.6_013:

Setup ThinOS 8.6
Setup ThinOS 8.6

That’s it, feel free to ask questions and leave comments below, thank you!

Ps.: This method might also be useful, if you ever encounter a bricked device.

Author: Marco

Marco is an IT-System administrator and IT-Consultant with 10+ years experience. He is specialized in the delivery of virtual Apps and Desktops with Citrix solutions. In 2017 he has been awarded Citrix Technology Advocate by Citrix for his community work (#CTA). His second core area is availability & performance monitoring with Zabbix, a leading open-source solution. His employer is the German IT-Company ANAXCO, which is developing a Transport Management Software (TMS) based on Microsoft Dynamics AX. More about Marco

24 thoughts on “HowTo: Dell Wyse ThinOS Downgrade from 9.0 to 8.6”

  1. Thanks Marco, I used this after a firmware bug I found in 9.1.113, however when downgrading from 91.113 I found you have to disable secure boot in the bios or you can’t boot to the USB stick

    1. It does not work for me on 5070. Keeps getting an error code 233.

      If I pull an image from a working 5070 with 8.6, and try use that to downgrade a 5070 with ThinOS 9.1, I also gets error code 233

      1. Had the same issue.

        Try the following:
        On the USB-stick you’ve created browse to the image-folder and open the Commandsxml.xml file and change FFFFFFFF</mask into 00000000

      2. My fix for this on a 5470 was to edit the commandsxml.xml (found in the image-folder on the USB-stick).

        There is a ‘FFFFFFFF’ section and when you replace this with ‘00000000’ it should work.

        1. I did the change from “FFFFFFFF” to “00000000” and disabled secureboot

      3. your firmware version is simply wrong. there is pcoip and no pcoip release and when the version does not match it give 233 error on upgrade process

  2. Thank you very much, DELL-Support is awful, instructions on the web are totally faulty … my problem is, that after the USB-Boot it shows no image-file to choose, despite the fact that I prepared the USB-Stick exactly as you have written.
    Regards, Alex

  3. I have the same situation. Prepared by USB. Booted from a flash drive. The menu for selecting an image for installation appears. But there are no images in the list.

  4. Would this work to image a 3040 with ThinOS 8.6 to 9.1? I went through the process and it seems to have gone gine (no errors) but the device still boots into 8.6. Weird.

  5. Thanks a lot for your guide.

    However, i get stuck in 100% of the process…

    “Operating systems (In Progess)…”

    100% stucks, don’t get the “done” image.

    Any idea?


    1. Can confirm, tried again today, with the same version of the Imaging tool and the same version of the Merlin rsp file, and now I get stuck at 100%. Still searching for a solution.

      1. Thanks for this great tuto Marco, it worked fne for me.
        Regarding the process stuck, I simply turn off the Wyse by pressing the start button. The downgrade process was sucessful once booted up.

      2. also had the same problem it was stuck on 100% but i just restarted, adn removed the usb, it continued to finish up the setup, all was good

    2. Yep – does this – just wait a few minutes after 100% is shown, then power off teh device, pull the USB drive and power on – setup should then complete.

  6. Same Same 🙁
    However, i get stuck in 100% of the process…
    “Operating systems (In Progess)…”
    100% stucks, don’t get the “done” image.

    Downgrade from ThinOS 9.1.2101 to 8.6 -Merlin Image 8.6.710

    100% Stucks – 🙁

    Please help me

  7. Also did not show the USB drive in the boot menu for me. In addition to disabling Secure Boot, had to enable the Option in the BIOS Setup -> “Enable USB-Boot” under USB Settings.

    Sollte der USB-Stick in der Boot Auswahl nicht angezeigt werden, gehe mit F12 ins BIOS Setup und dort muss unter USB-Einstellung, “Enable USB-Boot” aktiviert werden.

  8. Confirm: changing the Commandsxml.xml file and change FFFFFFFF into 00000000 works

    Dell USB tool 3.1.
    ThinOS downgrade from 9.3 to 8.5_115 PCOIP optimize Wyse 5070

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