We have a samsung tv model pn51e550d1fxza. We were using it off and on all day. Then one time we go to turn it on and the little red light just did double blinks 5 times. No backlight no nothing. Everything else on power strip is still working fine. Tried leaving it unplugged for a while and still nothing.
Plasma huh. They don't actually have backlights. I would say it is time to replace it rather than make an attempt at repairs. The last manufacturer of Plasma TVs shut down a while ago. OLED TVs are the new high quality standard, but you could get similar quality out of a 55" LED TV for only a few hundred dollars. OLED is still above $1000 typically.
Plasma TVs work by exciting gases with high voltage for each sub-pixel, so the circuitry in there is none too safe to work around without experience. They also consume a lot of electricity compared to newer designs.
Re-capping is sound advice, but he skipped the part about troubleshooting and finding out if that is the problem. If you don't already have the tools this can be a moderately expensive repair, and it may not solve the problem. Also note he is working on a LCD panel, not Plasma. Those are mostly high voltage (AC input) to low voltage circuits. Plasma circuits need to create even higher voltages and aren't all that safe to work around unless you know what you are doing.
Older LCDs with Fluorescent backlights also have high voltage circuits.