Screen brightness stuck at max after updating to Windows 10 version 1803 (build 17134 / April 2018 Update)

Hi

I just updated the Windows 10 Home installation on my laptop to build 17134 and now I can't adjust the screen brightness. It's stuck at the highest brightness setting and while the brightness slider moves up and down it doesn't change anything. I tried deleting the display and graphic drivers and reinstall them but it didn't solve my problem. My laptop is an old lady so it no longer receives driver updates. Any suggestions?

Specs: https://support.hp.com/ee-en/document/c02286076

HP Envy 14-1090eo

2.4 GHz Intel Core i5-450M

ATI Mobility Radeon HD 5650 1GB DDR3 (Switchable)

8GB (2x4GB) Samsung PC3-12800 DDR3

Samsung SSD 850 EVO 1TB

Display drivers:

- 1. Primary: Intel® HD Graphics (Core i5)

Report Date: 4/30/2018

Report Time[hr:mm:ss]: 23:53:55

Driver Version: 8.15.10.2900

Operating System: (6.2.9200)

Default Language: English (United States)

DirectX* Version: 10.1

Physical Memory: 7989 MB

Minimum Graphics Memory: 32 MB

Maximum Graphics Memory: 973 MB

Graphics Memory in Use: 115 MB

Processor: Intel64 Family 6 Model 37 Stepping 5

Processor Speed: 2394 MHz

Vendor ID: 8086

Device ID:  0046

Device Revision: 02

**- 2. Secondary:**ATI Mobility Radeon HD 5650

Radeon Settings Version - 2016.0226.1531.27895

Driver Packaging Version - 15.301.1901-160226a-299900E

Provider - Advanced Micro Devices, Inc.

2D Driver Version - 8.1.1.1533

Direct3D® Version - 9.14.10.1171

OpenGL® Version - 6.14.10.13417

OpenCL™ Version - 2.0.4.0

AMD Mantle Version - 9.1.10.99

AMD Mantle API Version - Not Available

AMD Audio Driver Version - 10.0.0.3

Moved from ( Windows / Windows 10 / Windows update, recovery, & backup )

did new cumulative update fixed brightness issue?

No KB4100403 (OS Build 17134.81) didn't solve it. But this solution from Ferdz Amp with a minor tweak did.

For those still encountering this issue, I recommend that you follow these steps and see if the issue persists:

1. In Windows start search box, type in regedit and hit Enter.
2. Navigate to the following key:
   • HKEY_LOCAL_MACHINE/SYSTEM/ControlSet001/Control/Class/ 4d36e968-e325-11ce-bfc1-08002be10318 /0000
3. Double-click the item of FeatureTestControl, set the hexadecimal value to "fb20", and click OK.
4. Reboot your computer to reflect the changes.

Registry Disclaimer: The steps mentioned here includes system registry modification. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow the steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: Article ID 322756.

Let me know how it goes.

The written location for FeatureTestControl was different on my system and is located in:

• HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class{4d36e968-e325-11ce-bfc1-08002be10318}\0001

Please be aware that after doing this edit selecting the lowest level of brightness will turn off your screen. This also means that if you are running on battery (laptop) and you select the power mode "Best battery life" or Windows automatically switches to "Best battery life" upon unplugging the charger, your screen will be turned OFF! This is not a major concern since you can just turn up the brightness to the next lowest level via the FN+F3 (key combo might differ on other laptop brands) keyboard control shortcut and the screen will be turned back ON.