Why does the backlight flicker after screen repair

"I am a new tech and am always very careful with the flex cables while installing. I test out the screen before every installation, and then after fully installed, they flicker! I've been getting the same problem, even after we started buying from only our ""good"" suppliers, with 50% or more of our screens. It has made me very self conscious, thinking I'm damaging them somehow. Glad to know this is likely not the case!

Update

Someone sent me a PM that said you must manually power down the device before unplugging the battery. I have not had any problems with them since! Before, when I would test a new screen, I'd just unplug the battery to complete the installation. Now, I make sure the power flex is plugged into the logic board so I can manually power the screen down before completing the repair. Even our crappy supplier's screens aren't flickering with this method now. Hope this helps!

Update 2

As long as the device is powered down OR you have dimmed/locked/turned off the screen, the backlight issue does not present itself. I have not had a problem with them since I learned this a few months ago.

Even so, the flickering goes away after a bit."

"I have come across this problem several times and I have found the reason why. It usually happens when you disconnect the screen or the battery without shutting the phone down properly.

Once the screen flickers, just turn the brightness down until the flickering stops. After some time passes, slowly increase brightness so that the flickering is not noticeable, after some time you can increase the brightness to full and the screen will be fine.

I tested this out on several screens and it does occur when disconnecting the lcd or battery while powered on."

"I know this thread is kind of old, but I deal directly with a supplier in the states and I've asked him what the problem was with his screens recently. He supplies great screens and I've rarely had any issues, but as of late I get about 50% with the flickering back light. This issue doesnt start until about 20 min after install. He told me the issue was that the glass on top of the digitizer is either too thick or too thin. Its an issue with the manufacturing process. Basically, whether its too thick or too thin causes undue pressure on the back light. Too much glue or thick glass, if that makes sense.

Hope this helps."

"hello there.

I agree with iwillfix.

I found that original lcd (the one with the black stripes left and right only have this problem extremely seldom.. but the copy/half original LCD on the cheaper displays have this problem much more often.

a burn-in of about 15 minutes to several hours will fix this problem most of the time.

Since we offer to repair the displays within 30 minutes for our customers.. i tend to buy the original lcd displays... but i tested a new supplier who said it is original but it is not.. ugh... so i have to write a formal paper now to inform my customers about this burn in procedure..."

"It happened to me after I replaced a screen. I totally agree with iwillfix.

A lot of people say you must turn brightness/auto-bright off/on, wait a little, sing a song, yadda yadda, but if you just wait you're good to go."