If so, keep reading!
Once you've removed the shield covering the connectors, STOP. What do you do now? Well, depending on which YouTube video you watched, you're either going to make a backlight mistake, or you'll do it the right way! If there's a single fundamental lesson about working on electronics you should know, memorize, and put into practice, it's DISSCONNECT the power before starting ANY repair - no matter the voltage or current levels! Many people have been electrocuted by working on live wiring or circuits. And while you may not be electrocuted by working on your iPad, there's still plenty of damage you can do while tinkering around in there with the power supply being connected. So rule #1 when working on ANY electrical devices - DISCONNECT the power!
Do not work on any phone or tablet with it plugged into its power cord OR with the battery plugged in! The exceptions to this rule would be if you're actually testing a circuit with a multimeter and you need the electricity flowing. The other includes iPods and some tablets where the battery is soldered in place. I've worked on plenty of those without issue. BUT, when you can disconnect the battery, DO IT, before doing anything else. If you use metal tools while working on a device with the battery still connected, you are BEGGING to create a short circuit and blow something out.
So why does the backlight stop working on an iPad mini? Working our way from the LCD FPC connector towards the backlight circuit, we run into the backlight filter first. Many refer to this as the backlight fuse, but it was never designed as a fuse and IMO, shouldn't be called a fuse. A fuse is placed into a circuit, expecting to blow in a power surge, and designed to be easily replaced - like the fuse box in your car. The backlight filter is neither a fuse, nor easy to replace (for most people). Special tools are required to replace it - including a good microscope (not what you used in science class or came in your home chemistry set), a very small soldering iron or hot tweezers and some soldering skill. After the backlight filter is a diode, and after that a coil. So the chain were the problem occurs flows like this: LCD with a plug with metal pins at the end of the FPC > LCD FPC connector, also with metal pins > PCB trace > back light filter > backlight diode > back light coil - and we're going to stop here because the damage done applies in this chain of components. The LCD FPC connector is soldered to ground (negative side of power source) - remember in DC current, electrons flow from positive to negative and will ALWAYS take a short cut (path of least resistance) if you provide one (ie, metal tools in a live circuit). The hot pin (providing power to the backlight circuit) is about a millimeter away from ground. When start your repair, leaving the battery connected, then when you're done, you don't get the LCD FPC plug lined up with the FPC connector just right, you will blow the backlight filter when you short the circuit. It's also possible that the backlight diode can be affected. But, as our good friend Jessa at Mendon iPad Rehab likes to say, "It's never the coil". And it's not. That's not to say the backlight coil can ever fail, it just doesn't fail under these circumstances. This is contrary to many corners of the internet selling replacement backlight coils and advice as though it's a real problem, and why you should seek out repair advice from reputable sources and not pick the first YouTube video or Google link you come across offering solutions for your problems.
So what's the take-home point here? Always, always, always unplug the battery from ANY electrical device you're working on BEFORE unplugging anything else, or sticking metal tools into the circuit. We've all had a screwdriver slip off a screw and go places we weren't intending, if that driver blade bridges a + side of a component to ground with the battery connected (EVEN if the device is off), you can blow components out. I say even if the device is off, because despite the device being off, there are a limited number of circuits still connected to the battery and shorting them CAN burn things out.
And now for a little cartoon I made. If you understood what I just wrote, you'll understand this. If not, read it again. :)
For those who don't know what a filter, diode, or coil look like, here's your hint: on the left is a filter, the middle is a diode, and the right is a coil.
A (very) short story to summarize this post:
Once there was this iPad mini, which was very popular in the land. Then, one day, it was pushed to the ground by a bully and cracked in a scheme that seemed a little too planned. It was rushed off to have its screen replaced - by someone that knew just enough to be dangerous who answered the call. After they were all done, the iPad turned on and there was an image on the screen, but the screen wasn't bright. In fact, it had no light at all.