The T9 Headunit that I purchased from Amazon seller YUZHONGTIAN had a terrible whine to it whenever the screen was on. It was a very high pitched, dog whistle type sound that only got worse as the screen brightness was lowered. I worked with the seller for awhile to try to get a replacement, but we weren’t able to find a unit that worked. Before I gave up, I decided to see if I could fix it myself. Turns out this is a very easy fix for anyone capable of installing a radio themselves and only takes a few minutes and a small screwdriver.
If you screw this up, you will trash your radio, possibly harm yourself and 100% void your warranty. Ask for help before you over extend yourself.
First, unscrew the 6 phillips head screws (two other screws are in the middle. I suck at camera) that hold the radio chassis to the screen frame. The radio is connected to the LCD board with a ribbon cable, after you undo the screws, do NOT just pull off the radio body. You need to gently lift it straight up an inch or so in order to clear the standoffs, keep an eye on that cable!
Next, lay the radio chassis down so that none of the metal chassis touches the LCD driver board. This is pretty important if you are going to power on the radio while you make these adjustments, less so if you are not but still important so you don’t damage any of the circuits.
Lastly, in the upper right hand corner of the LCD drive board, nearest the emergency flasher button, you will see a small potentiometer labeled VR2. You need to turn this between 1/4 and 1/2 of a turn counter clockwise. Ideally you would use a ceramic or plastic screwdriver for this, if you don’t have one then just make sure the radio is powered off when you adjust it.
DO NOT OVERTURN THE POT! It will break, you will be sad.
That’s it. If you turn the radio on and it still has a whine, adjust that pot a bit more until it goes away. Screw the radio back to the LCD frame and enjoy your dog whistle free T9!