PocketBook 912 screen voltage adjustment

[pocket]

Hello, as my curent ereader recently died , I decided to revisit my old beloved PocketBook 912. It's screen was broken, so I got another one from taobao, and replaced it. The result was encouraging (screen worked) but sub-optimal: the color was greyish and fading, the text barely readable.

Now I came across a website, which provided a hint why this may be the case: Every batch of screens has a residual charge compensation voltage VCON, which is from 1.00 to 2.5 V. The required value of the voltage is indicated on the screen in a separate loop tag (look at the upper photo). If after installing the new display the screen is not clean and there's a big amount of "rubbish" you've to regulate the voltage of VCON. In some models of e-books is a resistor on the board of the device for regulating it, in other models is is done programmatically with a help of special utilities. link

The original screen in my ereader had a "-1.25" VCON value on a sticker on the screen. The new screen I installed has a "-1.39" VCON value on the sticker. So I thought maybe adjusting the VCON voltage could do the trick.. but how? I found something that looks like a miniature knob on the circuit board labeled with a "VR2". This might be be the place to regulate it. I tried to turn it while the device was on and then restart the device, but I could not see any noticeable difference.

Does anyone have experience with this? Do you think adjusting the VCON voltage could improve the screen contrast? Or am I going down a completely wrong path? Any other advice what to do with a washed out screen like this? I will be grateful for any advice.