Screen goes black after showing Samsung logo in Samsung Galaxy S3 I flashed Cyanogenmod on my Samsung Galaxy S3.  I did this process through a program called Odin.  Once I reached PASS! on the Odin screen, I disconnected my cell phone from my laptop as directed.  I did notice that the cell phone did not reboot during the process.  The cell phone did completely shut off.  

The process then indicated that I was to look under Settings to see if I had a SuperSu app.  So I thought the next step would be to turn on the cell phone.  The cell phone does attempt to turn on and shows in the upper left corner recovery booting and the center of the screen says Samsung.  However, the phone goes black almost immediately and will not turn on at all.  

Do you know what have I done wrong during the flash process to remove this particular Cyanogenmod?
Cyanogenmod might not be removed but if it did not get written on the partition. There is many reason why and not necessarily your fault. If you really have to know depending on a what stage the bootloader is at in loading the system. Really, what needs to happen is the kernel needs to load to point that it starts talking so that we can possibly intercept what its saying.

Alright there is a few weird things going on but the good thing is there is only a little sign of any doomsday alarms going off. the little on is when you the reboot when it did not turn back on are you 100% sure it totally shut down? There is a possibilty that though it looks off its not totally When you explained what was going on when the device was turned on. To verify that this pull the battery for a minute or push and hold the power button for 30 seconds then try to reboot. If its still not starting plug it into the charger and try to reboot incase it was not shutdown and the battery fully drained. 

If just pushing power and it attempts to load into recovery instead of the Operating system is rare like some matrix stuff. If everything is normal then it explains the process of booting into the recovery. The crash that followed is usually because of not releasing the power button causing a kinda forced crash. Why forced because the emergency override shutdown is to hold the power button down for 30 second. By the way if at any point in the process you get in a boot loop that's how to get out. 

Next what exactly was your end goal was it to run a custom ROM. Trying to Root or flash a custom recovery to root or all of the above. Since I'm unclear of the exact process and the steps taken its best not to assume. Let's try to tidy things up within your device with a data/factory rest to clear up the cache. 


Completely power down your device.
Once its totally off press and hold.


  press and hold the volume up botton + home button + power button all at the same time as soon as you see the Galaxy S3 symbol release the power button.

Hopefully you will boot into recovery and to scroll through the menu use the volume up or down.
Go to data/factory reset press the power button to select.
Next a list with a lot of no's and one yes scroll down to the yes and use the power button to select and so the process beginds.
Lastly if use the power button to select reboot system now.


If you were unable to get into recovery or the system fails to load. All is not lost there is an ace in hole that Fix's the majority of software issues. Flash a factory image (return to stock) through Odin but there is some prep involved. If you want some more details as pertaining to your specific device let me know your S3 model number and service carrier. The software is different between s3 variants and service carriers.

You need to get the factory firmware. The worldwide web has a lot of choice some of them are highly questionable. Be sure to check that the md5 stated matches up with the md5 on the software along with file size. I am a bit paranoid when it comes to free software but the lack of trust is a two way street. Summing it up that's why Samsung does not officially support the release of their software. With that sammobile.com has a wide variety of Samsung firmware and has a high public trust rating. Regardless of rep always double check. I've seen this happen a lot so must warn you that without cause Do Not select anything involving re-partition
Or PIT


hook-up your device to your PC and get confirmation from Odin that they are visible and able to talk to each other in the upper left corner.
Select PDA and then browse your system files and get the TAR file type you downloaded
hook-up your device to your PC and get confirmation from Odin that they are visible and able to talk to each other in the upper left corner.
Click the start button and I just  don't touch anything while the process runs to try to limit any communication errors due to user interactions. Once Odin finishes it will reboot the device. Since its new firmware it could take a while to load the first time. Wait a minimum of 20 minutes personally though I wait 40 minutes before considering it a failure to launch. Once I saw one persons system load after 5 hours but that just had to have a prayer some luck involved.


Hope fully your up and running again but if not there is still a few things that can be done. If you run out of options and absolutely want this thing going. There is one thing that can be done but that's overy head it involves soldering. Pictures below for reference from Danarama at XDA guide to Odin