Sony WEGA KE-42M1 sound but no picture.

If the power supply did not help instead of guessing it may be time for a shop to look at the set.

If the problem is same with different input devices and you have ensured the are no loose contacts in power outlet, RC jack, cable and sockets, the TV needs servicing.

This confirms that the main power supply which is the SMPS is faulty.
The fuse could have failed and must be checked, if the fuse fails the SMPS is confirmed to be faulty due to the power outage.
please check the links below for tips and support:

http://www.fixya.com/support/r5826301-working_switch_mode_power_supplies

http://en.wikipedia.org/wiki/Switched-mode_power_supply

it is posible to repair ...but it is very coastly . you are going to repair this plasma same price u will get new plasma .it is my best idea

Sounds like your TV is giving out, plain and simple.

If this doesn't sound right, then only one thing comes to mind. Have you moved the TV recently? Are you using a different coax cable, (if using cable that is). If so, just change the cable back to the previous one and you should be fine.

el televisor lo prende y se oye, pero no se ve. hay veces que lo prendo y se ve.

IT GAVE OUT A LOUD BANG AND NOW I HAVE NO PICTURE OR... Mosfet Transistor blow out.  Transistor K3316 or replace the Power unit supply. This problem was caused by a low power voltage. SONY SONY KE-42TS2U

did you ever get your tv repaired?

SOUNDS LIKE ANOTHER LAMP. WHICH MAY JUST BE BAD LUCK. PROJECTION LAMPS CAN GO OUT IN ONE DAY OR LAST TEN YEARS THERE SUPPOSE TO AVERAGE 4000 TO 6000 VEIWING HOURS AND THERE ARE MANY DIFFERENT FARIABLES THAT CAN AFECT IT. IM ASSUMING YOU HAVE A KDSR60XBR1 WHICH HAD A PROBLEM WITH THERE OPTICAL BLOCKS. I HAVE REPLACED MANY AND NEVER HAD A CALL BACK YET IN REGAURDS TO THAT BUT LAMPS ARE A DIFFERENT STORY. I WOULDNT WORRY IF I WAS YOU BUT IF THIS NEW LAMP GOES OUT SONNER THAN EXPECTED THEN I WOULD LOOK AT THE BALLAST IT IS WHAT POWERS THE LAMP