Tc-p42st3042 tv was on, screen went black red led on, unpluged turn on red led no flashing

SOURCE: Plasma TV

did you hear the sounds? or maybe you have defective power source in hot side..

SOURCE: Panasonic 32 inch LCD TV will not turn on-red light flashing

The number of flashes is an error code. Count the number of flash. It looks like one of the boards in your set is failing intermittently. Panasonic codes for a guide as a starting point. Exact board STILL has to be verified;
One Blink: One blink of the power LED indicates a problem in the inverter circuit located on the LCD panel. The inverter board is not to be repaired in the field. Therefore a replacement is required.
Three Blinks: Three blinks of the power LED indicates an over-current or over-voltage condition in one of the DC supplies of the AP board. The AP board is repairable. Therefore the use of an ohmmeter and peak-hold-voltmeter is required to determine the cause of the shutdown. An over-voltage condition is definitely a defect of the AP board. An over-current condition may be due to a short circuit located in the AP board, A board, or the LCD panel.
Five, Seven, or Eight Blinks: The A board is responsible for five, seven or eight blinks of the power LED. The MAIN +3.3V, MAIN +5V, and MAIN +9V sources are all produced on the A board. The detection input pins of the MPU, IC1100, monitor for their presence.
Four or Six Blinks: The AP board is responsible for four or six blinks of the power LED. The DTV9V, and SUB_5V sources are produced on the AP board. The MPU IC1100 monitors for their presence when the unit is connected to AC Power. A short or open circuit on the A board may also be responsible for their absence.
Nine Blinks: Nine blinks of the power LED is due a short circuit in the audio output circuit (s) of the unit. The audio output circuit is located on the A board. Confirm the status of the speakers. If defective, perform a replacement. If ok, replace the A board.
Ten Blinks: Ten blinks of the power LED indicates a malfunction of IC4200, the frame converter. This IC resides on the A board. Therefore ten blinks of the power LED requires the replacement of the A board.

SOURCE: Panasonic Projection HDTV Made 9/2003

my problem is that when i turn on my t.v there is the sound that the t.v turns on but there is no picture on the sceen and everything is fully black....

SOURCE: Lamp problem or else?

You need to get the ballast repair kit #LSUC0002 and replace the parts to your ballast.

I have the exact same TV, did the above this past weekend, and the TV works like new.

You need to know how to solder though. It's not that hard.

SOURCE: Sharp LC37D44U Power LED was flashing green. TV

I had the same problem. all the service reset would only make the display come on for a few second with no "k" on the screen - only the channel would show up. I purchased a complete set of board for the lcd on ebay, and started swapping them one by one. The inverter boards were the culpret. Tele working 100% since that board swap.