I have an issue on my device (Galaxy Tab S 8.4). I´m either stuck on boot loop (flashed with TWRP that worked fine for months until recently after a restart) or I can enter download mode and get stuck at the "Download... Do not turn off target!"-screen. Cant ever enter recovery no matter how I try... If I let the battery die it boots up into the boot loop as soon as I plug in the power chord. Is my device bricked or whats going on?
I had the same exact problem. I flashed a Marshmallow ROM from KitKat, not realizing I had to update the bootloader to Lollipop. I got stuck and couldn't get past the boot screen and when I used pwr+vol dwn+home I got the Download...Do not turn off target msg. What worked for me was to plug in my Tab to my pc, start up Odin 3.09 (not sure if the version matters, I didn't try 3.12) and I was able to flash the Lollipop boot loader. The Tab restarted and I was good to go. Hope that helps
Not enough data in question - and not enough rep to ask with comment, do you try to enter recovery by holding
volume up + home + power? (You mentioned just letting battery die, which is not going to help any good). You mentioned You can enter download (
vol down + home + power) so I'm guessing you know about recovery too.
If You cannot enter recovery even holding proper combination You need to flash just recovery.img, preferably checked and working with your model.
I have exactly the same problem Jakob has described. The Tab S is stuck in in a boot loop. The power off button has no affect. Vol Up + Home + Power has no affect, Vol Down + Home+ Power reboots straight into the boot loop. The hope was that letting the battery drain to power off, then charge to try Vol Up + Home + Power ( as this should be done when the device is already power off). The action of charging sends the device back into the TWRP boot loop. The Tab S had been working great with CM12.1 for many months. But after a factory reset, which I did in order to be able to gift this to someone else, has resulted in this situation.