There are two ways of turning this tv off. A ''Main Power'' button directly on the TV which turns it completely off or using the ''Standby'' (a mode which turns the TV off, but will leave a red light at the bottom of the screen) mode which is activated when using the TV remote's Power button or to press the Standby button on the TV. The only way to turn on the TV with the remote is to leave it on Standby mode, and that has been fine for the long time I have owned this TV. But one night I used the remote to turn it off (putting it on standby mode) and quickly remembered something I wanted to record (with my DVR). When I used the remote to turn it back on it turned on normaly, but then quickly shut back down to Standby mode. I tried turning it back on using the remote, but the button was not doing anything. I tried pressing the Standby button on the TV but that didn't work either. I then pressed the Main Power button on the TV and the TV shut down normally. When I pressed the Main Power button again it seemed as if it were working normally but then it shut

It sounds like a microprocessor that has latched up. Try pulling the AC plug and letting it rest for an hour or two, the problem may cure itself. The end of your message was truncated at ". . . working normally but then it shut . . ." Try posting the missing portion as a comment to your original.

Your set is of the crossover year where the first units had the same troublesome PS board as was in the 510 Elite of the year before, then they redesigned the PS board and had no further problems. Your model year contained both types of board.
To find out which board your set has, you have to follow the power cord and see if it leads you to a vertically mounted board, or a floor mounted board. If a floor mounted board, you may need local service help.
But if a vertically mounted board, please pay heed:
Your Pioneer 533HD series set has the classic cold solder joint problem endemic to all of this series of Elite CRT RPTV. The power supply - PS - board needs to be resoldered virtually completely. It's a time consuming, tedious job that if you get wrong, who knows what could happen when you turn it on again? So don't even think about resoldering it if you are an amateur at the soldering process.
I do this job every day then run it out in my test 610HD - same series - and then equip your board with a lifetime warranty on the resoldering work I have done. Please contact me directly, google Mr Bob and calibrations and Image Perfection. Unless you do resoldering every day as a professional assembler or are an experienced repair tech, I cannot in good conscience advise you to do this yourself. Far too much is riding on it.
However, if you are highly experienced at soldering, resolder everything but the heat sinks, the test points, and whatever has already been resoldered and is still glossy and gleaming, like fresh resoldering is. The solder used in the original assembly of that board was far too thin, which results in these cold solder joints.
And don't do it part way! Many joints that are not bad now will be soon, trust me, and if you have only resoldered just the ones that are bad now - the early ones to go out - and continue to use it, you make your board that much more susceptible to the far more dangerous ones that happen later on, which can damage boards downline from the power supply board.
I am the only repair person I know of offering a lifetime warranty. Even Pioneer does not do that. In fact I have permanently corrected many rebuilt Pioneer boards when they've gone out later. Pix are available at www.avsforum.com.
In your case chances are you have not heeded the warning signs of cold solder joints: intermittent ops, blue flashes, fluctuations in the brightness of your pic and other instabilities.
In the case where one of these units turns on then turns off again - LED in front goes green, then immediately back to red before a picture has a chance to appear - it's "going into protection". Chances are something downline has now been damaged because of the instability of the PS board, which is responsible for powering up the entire unit.
What I would recommend if it's "gone too far" and the unit will not stay on anymore, is a troubleshooting session with me on the phone, which is something I require before allowing a PS board to be sent to me for resoldering if the set's not staying on. Luckily, these sets were designed with on board diagnostics that can be read by technicians from far away.
If it goes green then stays green but no pic appears - even graphics like the Menu - then one of the cold solder joints that powers up the section that powers up your picture has opened up and is now staying open. This has always been remedied 100% by the resoldering process.
If it powers up correctly upon turnon from dead cold, DON'T PUSH IT! If it still has intemittencies, it's in a very precarious, dangerous condition. Many sets have been run past their warning signs, and by the time I get notified and can lend a hand, they are considered totalled and are abandoned. Don't let that happen to you. RUN IT FOR NO MORE THAN 40 SECONDS, and power it down again and unplug it.
DO NOT ALLOW IT UP TO NORMAL OPERATING TEMP AGAIN - EVEN ONCE - UNTIL FIXED PROPERLY.
If it turns on from dead cold and works properly even tho intermittencies have happened in the past, this is the best case scenario. It means it can be resoldered properly and you'll be home free. Or sent to me for resoldering if you are not a highly experienced repair tech or assembler, in which case you'll get my lifetime warranty on the resoldering work..

Mr [email protected]