Panasonic TC-P42ST30U No picture no sound. Red light on and steady. Clicks when you plug it in. No cange when Power button pressed. Already replaced power supply with good one from Shop Jimmy.

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: TV won't turn on.

hi i had the same problem,
did you check the fuse if it looks burnt out you can get a new one from a b&q or a hardware store

hope it helped

SOURCE: 4 blinking lights

I fixed it myself!
I bit the bullet and ordered a replacement Power Board for AUS$290 and swapped it out myself.
Only took ten minutes, most of that time was removing and replacing the 101 screws holding the back panel on!
Working fine again now.
I did sit the two boards side by side and noticed the new one had moved some of the micro components from the back of the board to the front plus some other small component changes.
If your handy with a screw driver and have some technical knowhow I recommend having a go at fixing it yourself as it wasn't hard and probably saved $200 in service charges (all this assuming you are out of warranty!)

SOURCE: red light flashes 10 times - Panasonic TH-42PX6U

hey there! i finally figured it out!! If you have a computer hooked up with the HDMI cable in the back of the TV and the computer is either on screen saver mood or sleep mood then it is trying to make the television go to sleep aswell. So the only way you can have a computer hooked up to the TV is if you use the front HDMI hook up. pretty weird but thats what was wrong with mine. Hopefully that was the problem :):) 

SOURCE: Blinking Red Standby Light - No picture

The six blinks indicates that an internal fan is either bad ot blocked by dust or debris, You should be able to look in the back of the unit and see some cooling fans. Chances are one on them is not turning and will need to be replaced