How to: 2010 iMac black screen lcd problem solved

hello everybody this is Abraham with Northshore computer services and today we have a very interesting problem in front of you are the two max there are 21.5 inch IMAX made in 2010 one works one doesn't the number one works the number two does not but it does not work in a very strange way I will explain what's going on let me put the screen on and I'll show you what's happening so I got the screen on it on the working one and I will show you what is going on so let me go ahead and turn it on as you can see just sick there was a Cortana at the door I had to tell her to go and do something with herself okay so this one here works fine I get hard drive disconnected so it won't boot it'll just give us an error which is fine let me do the same thing on the other one and then I'll start the explanation of what's going on and why it puzzled me so much okay I got the screen swapped and I'll explain why there is a screen swapping going on let me turn it on so I turned it on you got a chime and that's it the interesting thing about this computer is that it works if I have the keyboard connected and I tap on the keys I hear the bling bling and it seems as though the screen is bad that's what I originally thought now these computers have let me turn it on turn it off and start the explorations a few words about safety on these machines Mac is notorious at exposing high voltage contacts to persons who shouldn't be working on computers so even though these computers are now disconnected from the power there are capacitors that hold a lot of voltage and if you touch it it will zap you guaranteed and it will hold that voltage and I'm talking about 120 volts it will hold that for at least 15-20 minutes just be aware of that so no touching on these parts especially now that they've been hot so over off with the safety stuff so what was happening is my experience have gotten the better of me and I almost wanted to cry with these computers that I've been working on for quiet well with the broken one for quite some time and couldn't figure out the problem or official most of the time what happens is you get a bad card so these computers are notorious for bad video cards but this video card is not bad because it does produce an image and the chimes and it runs so the computer works it's nothing wrong with a video card I got another one for it I swapped it just to make sure that that's not the problem I thought that this LCD was the problem this is the LCD from this computer I took it apart because normally what I see happening is the light strip goes bad and what goes bad if you're interested in that in one of my videos I have how to open it up and how to get this fixed there are two connectors on opposite sides of this light strip and over time bad cold joins and you basically just need to reheat it reset er it and it works right back up taking it apart is a pain it's it's a it's not designed to be taken apart but it can be done I've done it I've done this one I'll put it back together it'll work this is the LCD I don't want to lift it but we get the idea so it's not the LCD because as I just found out it's not LCD so I tested the light strip with each individual LED and they work I plugged in this LCD into the working computer and it didn't show the image and I'll explain why I plugged in the non-working or actually the working LCD from the working computer into a non-working computer and I had no image so what was going on I thought at first that the inverter board is the one that's causing the problem here so I swapped the inverter boards by the way I didn't have the second computer to work on so I was working with one computer when you have just one computer it's hard to find the problem so I swapped the inverter boards didn't help the LCD would not light up on this computer no matter what you do I swapped the power supply because power supply cents the inverter board the power so I thought maybe that was somehow faulty by the way I do have multimeters and I do have oscilloscope it worked so when I was swapping I was like I'm swapping good parts and I know they work and no matter what I do the this computer would not light up the LCD and this LCD would not light light up on that working computer and the working LCD from that one would not light up on here it was a mess and I could not figure out what was causing this to happen it took me a little bit of time to recognize that the LCD has one connector that's for video second connector that's for temperature on a LCD this what causes the fans to rev up if you don't have this one connected there is another connector here and of course the LED connected so the reason that the LCD from broken computer didn't work on working computer is that I simply cut the corner if you don't have this one connected or this one or both it will not light up the screen I didn't know that on most computers all you have to do is connect your LEDs the light strip just to test and it'll work so I ended up tearing apart working LCD my fault but I've learned something because I cut corner and didn't think about it so I started thinking okay what's happening why is this one them not lighting up so I realized that what happened with this computer is somebody was at home replacing hard drive on the computer and when I took it apart first time the connector was kind of loose so I thought oh my god just a loose connector but I put back in never worked right this connector is broken and the interesting thing that I found out is if you don't have video going to your LCD it will not light up the LEDs this is totally bizarre this is something I did not know before where if you have if you don't have the upper connector connected if you don't have the video connector properly connected you will not get the light ground light on your LCD it may be something that everyone knows but me with my experience this was total news because I know from other computers other monitors that I fixed all you have to have is the energy to the LED and a backlight will come on now getting a picture that's different story but backlight will come on on these computers and I'm sure many other Apple computers if you don't have a backlight on your LCD it doesn't mean that the LCD is bad it doesn't mean that your video card is bad it doesn't mean that your LCD driver is bad it could be that the connector to the motherboard is faulty it could be that the motherboard is faulty I have not taken the motherboard out yet I had this motherboard out a hundred times and it's just something that never occurred to me I was fixing the backlight from my experience backlight kind of weird issue on these computers like I said these these connectors go bad and that's what was interfering with my judgment as to diagnosing why this computer wouldn't light up the LCD and I was shining a light at the LCD and I didn't see any image on there so I thought well maybe it's just too dark some LCDs are not particularly easy to shine the light on most of the time you cannot have the backlight you can take a very powerful LED light or you can take light from the camera and you'll be able to see at least traces of the image on and that will tell you that the LCD and the signal is working and properly connected on this machine this was a trick that the the LCD did not receive an image from the motherboard either faulty connector and it's not the wire that goes between the LCD in the connector because it is the same thing with every wire so I'm suspecting it's either the motherboard one bed or the connector so I'm gonna take a look at that so what is this video about if you have an iMac you turn it on you hear chime you punch on a keyboard sounds like something's working you you see nothing on the screen no backlight no nothing you shine the light on it and you see no picture on the background don't assume right away that your LCD is bad it could be the connector or the motherboard that's bad and I didn't know that by just connecting the LCD to the driver board or I should say they're back back liabilities to the driver board will not light them up not enough to just have the lights connected to the driver board and I can show that so here's a working computer we know this one works let's connect the lights power cord in and by the way if you don't know what you're doing don't do this at home I'm not taking responsibility for somebody's accidents at home it actually sometimes blinks let's see if it's gonna play nope didn't blink so as you can see it's not enough to have the LED strip connected to the power source you also have to have the driver board activated and that's what this little connector up here is for it tells that the LCD is receiving an image and you can start displaying it by turning on the back way it's kind of weird but I don't understand why it needs to be done that way it's just something that creates more confusion why it's not lighting up but that's basically what Apple did so you can see that the and by the way these LEDs run on 40 volts or 42 volts so I've been testing and I've been trying to get that LED strip working so I found out because you can't really test anything over here unless you have the LCD on and LCD has to be plugged in and working for that to start showing it to you know turn on the light so it's not easy to put a voltmeter on here to see how many volts at bronzong I'm sure there is an override that can be jump jump up in my case here it wouldn't help because I don't think image is being sent to the LCD itself so I'm gonna have to see what the problem is but as you can see it's not enough to just have the light connected to the driver to try and see if it's going to light up it is enough on other computers though and I'm sure fewer and fewer are gonna be where you can connect and test them so that's what I have it is a bit disappointing that I had to tear apart this working LCD but I write it off as learning so hopefully this helps somebody and my videos are to show somebody who is working in this field what kinds of problems that I come across and I hope to help those people have a little less frustration in life so if you don't understand what I'm talking about go watch cat videos this is technical stuff for those who understand and those that do understand I hope you like it thank you have a good day save money as always

Channel: Tech Services

Views: 117,021

Keywords: imac, lcd, problem

Id: dMSwjGJHvDQ

Length: 17min 19sec (1039 seconds)

Published: Tue Feb 26 2019