Powering on and off instantly

You either have a short in the unit somewhere, shorted high voltage section or a bad power supply. The most likely culprit is the high voltage section. If you are familiar with television repair, safety and good with a DMM and soldering iron you should be able to fix it. Check the horizontal output transistor (large transistor on the heat sink around or near the flyback. flyback is generally on the right side of the board and has a large red wire coming out of the top and going to the HV divider block.) If the transistor checks shorted, replace the transistor and flyback. Check all associated resistors and semis for any problems and replace anything out of spec. This should solve your problem. I have seen units with a bad HV block too so you may have to replace it also. If the HOT checks OK or replacing the HOT, flyback and HV block doesn't fix your unit you may or may not have the skills to troubleshoot the power supply and/or look for shorts in the unit. Certainly any charred components would be suspect. If you are not qualified to look any further you will have to have a qualified repair tech look at your unit. Good luck and be safe.