Hi, A bit late to the party, but I thought I'd bricked my old faithful UE40D5520 yesterday. On a whim I decided to upgrade my firmware for a fresh, new futuristic experience. Instead, it got stuck in a boot loop repeatedly showing the startup screen just as the OP described. Luckily, I found how to do a factory reset on a couple of other forums. This worked for me- I turned it on, waited till the Samsung SMART TV screen appeared, then pressed: MUTE 2 5 8 EXIT buttons (in sequence) on the remote. It did nothing for at least a minute or two, then it said it was Upgrading and I had my TV back working again! I also found this possible key combination on another site: On the remote, press Mute followed by 1, 8, 2, Power in sequence. Might need a different combination for your model, but worth trying it. A lot cheaper than a new TV!
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