Have just fixed an ipad with no backlight. After much work I tracked the fault to a short circuit capacitor on the logic board this held one of the gate inputs to a mosfet low and hence turned off the backlight driver circuit. I also have figured out most of the circuit for driving the LED backlight.

Ok here's an overview of what was wrong with my ipad...

This image is of a scrap board I had which I've removed the metal screening from. The red circle indicates the position of the short circuit capacitor (It's already been removed from the board in the pciture). Note this is the underside of the circuit board (i.e. that the side that's face down).

Its easy to check with a meter, if its short circuit then this is you problem.

This second picture shows the output from the LED drive circuit, the arrow indicates the point to test with a volt meter to confirm that the fault isn't with the voltage part of the circuit (The voltage should be around 18volts). You should be able to test this in place (you don't need to connect either the digitiser or LCD to check it), my tip is to use some pins soldered to your probes to make it easier to test.

This is the topside of the circuit board, you should be able to access this whilst the circuit board is installed in the ipad.

Ok i just had the same problem about 30 minutes ago with a cracked digitizer and had to replace it on the ipad 2. After the replacement i closed everything back up and realized the backlight wasnt working when it was before i did the replacement. so i had to open it back up and reseat everything this did not solve my problem.

LET ME NO IF THIS WORKS I HAD TO RESET THE IPAD BY HOLDING THE STANDBY BUTTON AND HOLDING THE DIGITIZER UP TO THE LCD AND TURNED IT OFF THEN ON AGAIN IT WAS THAT SIMPLE FOR ME IDK WHY I DIDNT DO THAT IN THE BEGINNING IT MAY NOT BE THE SAME FOR YOU BUT LET ME NO.

To resolve this issue you must restart your device by pressing the hold button and the home button at the same time, keeping them depressed for a few seconds. You will need to have a very strong light source directed at the screen when you are doing this. The LCD is still working, but it is nearly impossible to see without the backlight. Once you press home and hold together, a red slide bar will appear at the top of the screen. The reset will not initiate unless you slide the bar. A few short moments later, you should see the the white Apple logo on your display, backlight hopefully.

If you hold the power button and the home button at the same time for 15 seconds the unit will reset and the issue will go away. I have had to do this several times now. I do a lot of iPad repairs.

Dont have too much experience with iPads but have worked with LCD displays for over 10 years.

The backlight would be driven / powered by an LED driver board.

I would find out if the LED driver is integrated inside the panel.

As you now have 2 panels with the same fault I would guess not.

I would try and locate the LED driver and try replacing that or maybe even the LED driver cable.

Hope I helped.

I had this EXACT problem. replaced digitizer, screen worked fine, and then backlight went out. I had disconected the logic board while power was on, I had no choice because I had powered up without the digitizer connected to test it and as I found out, there is no way to turn power off without the digitizer connected. Above peopel suggested they created a short with the screwdriver, but I was meticulous, only using plastic.

Its a software issue, the logic board does indeed get "confused", and think the backlight is on when its not. Soft/hard resets didn't work, UPDATE THE FIRMWARE. for me it was rfom 3.2 to 5.01, as soon as I updated it the backlight came back on. If you dont need an update, try a factery restore and then an update.

Buy a can of contact spray and spray on the contact and cable. Reseat the lcd cable. This happens all the time when I am replacing LCD on unibody MacBookPros.

just remove and reinstall main battery connector to reset the system then it will come the backlight on your lcd

All you have to do is reset the unit, and the LCD backlight will be restored!

I had a similar problem with what appeared to be a blank LCD iPad screen after replacing the digitizer. However by shining a bright light on the screen I could see a very dim image. I was then able to reboot and this cured the problem.

Issue solved. Had the same problem when I replaced the home button cable and digitizer. I had no light on the display.

Solution for me: hold the power and home button for a while. When the reset was starting, the apple logo popped up.

Grtz Tim

Power off and back on restored my iPad2 backlight.

Thank you Peter.

Please try this -- hold down both home and power buttons for 15 -20 seconds then ipad will display apple logo then release both buttons.

I too had the same problem I unplugged the cable with an incorrectly spudger metal contact even seen it sparks thought to have created a short circuit and then the surprise of the backlight is not working.

I was provided with light and restored to like new after I turned it ipad.

rekindled the light has begun to function. I highly recommend everyone to leave the download ipad before removing the digitizer.

Andrea

Update

Now you can see if your monitor is functioning under a light?

Update

Hi fred,

The last possibility that remains is to do this test:

Put under a lamp and display at least the screen in a poor return ipad off from that state.

At the restart should be able to meet again the backlight.

If the problem persists, I suggest you take a look at this boat ebay, I read that you can repair the backlight of the chip with only $ 7! might be a good solution if the answers that I provided you can not come by chance.

http://www.ebay.com/itm/iPad-2-and-1-LCD...

Hope that helps.

Andrea

Update

Sorry , is soldered! remove this and re- solder new 4R7 !!! ;)

cheers

Andrea

"I too had the same problem I unplugged the cable with an incorrectly spudger metal contact even seen it sparks thought to have created a short circuit and then the surprise of the backlight is not working."

Hi Andrea,

I had exactly the same issue but I've tried your suggestion and I didn't work for me. Do you think it's possible that I have damaged the logic board??!

Thanks for you answer

replacing 4R7 is not an easy job. It's not a job with soldering iron and removing chit out and in. I repair iphones professionally and I even get nervous when I have to remove such and 6R8 on 3Gs.

If you want to get an experience with a chance of sacrificing your board, try it, otherwise look for a professional.

I am an ACMT. Though I'm not sure about the design of the iPad, on macbook pro machines there is fuse on the logic board built into the backlight. Replacing the LCD would not fix that issue, but a new logic board would.

HELLO PPL,

when i changed screen i cut through the vol button ribbon but i cut it after the vol buttons and before the power switch (so volumes were working power button was not)

power down ipad via removing the logic board of the battery DONT PULL THE BLACK SILVER BLOCK ABOVE BATTERY with the single screw in (you pull the logic board up off the battery connecters)

you will need to remove the 2 screws in the corners of the end of the logic board in plain sight not were the digitalizer plugs.

now put a plastic pry tool the lift the logic board there is a bit of tape underneath.

with the logicboard in the air one end you will see how the board connects to the battery.

simply hold off battery for few mins (press some buttons only to drain the bit of power on the board then simply put back together and re try the screen.)

if not working try and plug usb in to ipad as this will power it up then you will know if the button ribbon is damaged.

iPad2 Backlight chip is located here. This is the one you need to replace to get it working. I tried replacing the chips on the pix in this thread above, but didn't work.

ipad2 backlight chip location

yes.... I success ..disconnect battery and wait, discharge all voltage..reconnect battery_,,backlight is working

Exactly the same symptoms - second new screen, this time the battery was not drained and no backlight on reassembly. Hold down power and reset (ie rest the ipad) - it worked for me. Guess I'll just have to stop smashing it up now...:)

The reset option (pressing the home buttons and switching off) worked thank you so much I was about to panic ;-)

check the back light voltage on the back light power diode aprox 16 volt.

this is missing in set. ...get only 3.7v .. as per battery

steps

1 disconnect battery..

2 check voltage on back light power diode if charge remains

3 discharge with ground

4 reconnect battery

5 connect power adapter

and check back light

Always swicth off the Ipad before repair.

Had the same problem, afther software restore

back-light work again.

GSMdokter.nl

I made a youtube video on the ipad 2 backlight solution

if your ipad 2 was short because you forgot to turn off the ipad when changing the screen.

you want to change and replace

the backlight chip

and the backlight filter

and then if you ipad had water damage change the backlight 4R7 coil as well.

for more detailed picture showing where the ipad 1, 2, 3 backlight circuits is located please visit http://www.cyberdocllc.com/ipad-2/

I have fixed more than 20 ipad 2 logicboards with backlight issues so far. I havent have one fail with this solution just by changing these three surface mount components.

I have the same problem, but I just restarted the ipad and then it work :S

I had the same problem a while back but when I hit the power and home button my ipad shut down even though it didnt look like it was doing anything. then I plugged it into the power cable and it came back on. No problem since that issue.

i just faced same challenge and it was a result of using a metal to detach d screen connector from the board, but when i logged in here , i found out that we still haven't gotten a solution so i just prayed and repeated the process of detaching and attaching both the screen and battery connector, powered it on and the display light was back.

Ipad2 - I replaced the digitizer - same issue, no LCD backlight after replacement. I could not see any power off / dull image to power down and reset did not work. I had OS 5, decided to try and upgrade to OS 6 - IPAD2 came back to life!!! LCD is back. Yea!

Video solution How I fix the backlight problem in ipad 2

the backlight solution is out for ipad 1, 2 and 3

http://www.youtube.com/watch?v=K4zF3kQrz...

http://www.youtube.com/watch?v=Fqa5aZB6u...

http://www.youtube.com/watch?v=MkEznEwMd...

I fixed one using this method, it was pretty easy.

Hi Guys, Happy New Year

Ok so here is what happen. The IPAD Suffered Short Term Memory Illness. Well thats what we call it, lol.

If the LCD wont turn on, you probably was working on while it was running, still powered on or something similar, perfect example have you ever pulled ram from a computer while its on and see how it reacts?

Here a fix: Disconnect the device if its plugged in or connected to a PC

1. Take off the Digitizer

2. Remove the LCD

3. Disconnect the Audio Ribbon on the top left from the motherboard

4. Remove the control board cable (its the cable that runs in between the battery)

5. Disconnect the loud speaker cable or (charging dock ribbon)

6. Now if you have the WiFi Version, flip over the Motherboard and disconnect the cable.

Let these stay disconnected for about 3 minutes, Coffee Break!!

7. Now put everything back together, Make sure you don't turn on the device or have it connected to the computer while your reassembling the components.

Many Thanks

Just finished putting an iPad 2 back together after replacing the digitizer and the lcd would not turn on. Plugged headphones in and pressed play button and music came on...CRAP the iPad has battery the lcd isn't working and customer will be here soon to pick it up. Not looking good. Carefully took digitizer back off, reseated lcd, still nothing. found this forum, updated iOS. LCD light turns on, put everything back together and now it's good. ALHUMDULILLAH!

I have repaired several iPad 2 and 3 digitizers and never had this happen. I have been in the habit of leaving the device on so that I could check the lcd to make sure I don't burn it when melting the digitizer glue... Looks like I'll just turn it off from the start next time.

Thanks for the help people. :)

OMG! I thought it was a short circuit.. IT wasnt. LISTEN PEOPLE. your screen does actually turn on but you can't see it. under a specific amount of light you will be able. TURN IT OFF THEN BACK ON! I thought this wouldnt work BUT it WORKED! PRESS THE POWERBUTTON FOR 5secs THEN SLIDE YOUR FINGER TO TURN IT OFF EVEN IF YOU CANT SEE NOTHING SLIDE IT MULTIPLE TIMES THEN WAIT A MINUTE THEN TURN ON. (AND IT WILL WORK) ITES NOT A SHORT CIRCUIT.

I changed the broken digitizer of an iPad 2, and used what turned out to be a poor kind of adhesive to glue it back.

10 days later the digitizer became loose and I needed to re-glue it.

So I disconnected the LCD and digitizer, and cleaned the old adhesive using rubbing alcohol.

Before gluing the digitizer back, I tested the iPad and found that the LCD remained black.

I plugged the iPad to the charger and heard the charging sound, so the iPad was working fine.

I tested the LCD on a another iPad, and there it worked.

So I tried rebooting the iPad by pressing HOME BUTTON + ON/OFF BUTTON at the same time for 10-15 seconds, but nothing happened. The iPad wouldn't restart/turn off (I could still hear the charging sound when I plug it in).

So I shorted the 2 golden pins of the Home Button while pressing the ON/OFF Button for 10 seconds. This time the restart was successful, and the LCD came back to life. JUST MAKE SURE YOU DON'T SHORT ANYTHING ELSE AT THE SAME TIME!!

Turns out the home button was not seated well enough (especially that the digitizer was not tightly back in place).

So I recommend the following:

-Try the LCD and everything else before disassembly to make sure nothing was defective to start with!

-TURN OFF THE DEVICE,

-Do the repair/change the digitizer or whatever...,

-Connect the LCD, and digitizer but don't glue it back in,

-Turn on the device and test the LCD and everything else,

-Turn it off and finish the re-assembly and glueing.

First restart the ipad if it still doesn't work

here is a better pic of how to fix - IF it's a hardware problem.

http://www.emantechnology.com/temp/image...