50UX58B, I heard a poping soud and smelled burned plastic,

Sorry bad news these TV's work off of lights that shine thru the back of the screen if you heard a pop it was the power board that turns on those lights not an easy fix sorry.

Sounds like a High Voltage lead in the set is arcing--What I also remember from this set is there is a tiny blue cap (with back off and looking from rear) to the extreme right side of the main board that burns to a crisp.

That is fairly easy to fix.

Let me know what you find.

you may have just blown a fuse. check and replace with same size and type. if you smell burning, you fried something, and it may not be worth replaing on a 11 yr old tv.

Leave the back off and try to power the set on...be ready to pull the plug. Whatever is sparking/smoking is your bad part. On this TV I would suspect the flyback transformer or grey rectangular polyester capacitor mounted in front of a heatsink on the left.

It could be as simple as a fuse

Well that pop had something to do with the power components inside the TV frying. I would have to say there is nothing you can do to repair it as its dangerous to work on such things.
I wouln't waste my time bringing it to a repair shop they will probably tell you to just buy a new one.

Sounds like it could be a problem with high voltage stages. Definitely a job for a TV technician as it is dangerous try to repair it yourself.

Thats funny!My TV is doing the same thing,but now I hjave no picture just sound!

This may be an easy problem to fix. If you heard a pop sound, it's possibly a burnt cap on the powersupply. Check caps C521, C522, C517 or any burnt caps on the RA-3 chassis. Obviously be careful when checking.

This sounds like the small blue capacitor next to the horizontal output transistor shorted and cracked, which blew the B+ fuse. The B+ fuse is the solder-in type which looks like a small resistor and the value of the blue cap is usually 1000pF at 2KV.