My Mitsubishi WD-73734 turns itself off on its own. It was less frequent before. However, now after I turn the set on, both the picture and the sound come on, but in about 30sec the TV shuts off. It takes about 30sec before I can turn in on again, but it shuts off shortly after the picture and sound come back on. Any suggestions would be greatly appreciated.

SOURCE: Mitsubishi WD-52525

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SOURCE: white dots on my mitsubishi WD-73734 tv screen

Your tv is a DLP projection one. In it the image is generated by projecting light on a chip that is covered in tiny mirrors that reflect more or less the light towards the screen. In your case some of those tiny mirrors are no longer controlled - they are immobile and reflect fully the light so you get a white spot on the screen.
The DMD chip that holds the mirrors is dying and you will have to replace it. This is the only place i could find that claims to have it on stock. You can also go thru Ebay, in there you will find second-hand ones extracted from defective tv's.
It's installation is strictly a job for a person with great tv repair experience - too many thins can go wrong in there if the job is not done properly.

SOURCE: Have a 73" mitsubishi model No.WD 73734 and I have

On the TV not the remote, simultaniously press the menu and input button for at least 5 seconds. This should give an error code. If it blinks 3 times then a pause then blinks 2 times, the code would be 32. Get your error code and look in the service book at: http://www.audiolabga.com/pdf/V36-V37-V38_Service_Manual.pdf -

SOURCE: I have a Mitsubishi wd-73734'

Look for info in the Service Guide found here: http://www.audiolabga.com/pdf/V36-V37-V38_Service_Manual.pdf