I have a Panasonic Viera TC-P42ST30 plasma TV. While I was watching it, the picture and sound suddenly went off, but the red light stayed on steadily. When I tried to turn the TV off, neither the remote nor the button would do it. I had to unplug the set to turn the power off. The remote and button will both turn the set back on but still without sound or a picture, with the red light still steadily on. Again I have to unplug it to turn the TV power off.

SOURCE: Plasma TV

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

SOURCE: Power light flashing...TV won't turn on

Two flashes sugests that the power supply is faulty.It will have to be taken in to a service centre for repairs.

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.

Bud Martin

• 11361 Answers
• Posted on Jan 15, 2011

SOURCE: Panasonic TC-P42G15, plasma flat screen

Please check these 3 boards for blown fuses, bad caps, blown/shorted components.
Power supply, Y-SUSTAIN, and Z-SUSTAIN board.
You should download any one of the PLASMA TV training manuals to learn how PLASMA TV works from the link below, it will help you to get more understanding.

First, look at the screen in darkened room to see if you can see any slight glow from the screen, if it does, then the problem can be the T-CON (not getting the 12vdc) or the main logic board not feeding the signals to the T-CON board.
if not, next place to check will be the power supply module, make sure it has 24vdc which is required by the backlight inverter to work, the reason for not having 24vdc can be from bad DC filter caps (leaking/bulging top, high ESR) or short circuits in the inverter board which will cause the 24vdc supply to go into shutdown mode, so you may have to disconnect the power cable that feed the inverter board to see if the 24vdc will work without the inverter board hookup, you will need to apply about 3~4 amp of load to the 24vdc to make sure it can handle that. There are fuses on the backlight inverter boards also. So there is some troubleshooting you will have to do to find out the causes of the problem you are having.

If you are going to DIY and have proper tools, electronics knowledge, and know safety precaution then please read on:

Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors: http://s807.photobucket.com/albums/yy352/budm
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague
Parts: www.shopjimmy.com
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.
Or www.digikey.com, just make sure to use caps with low ESR, 105c, high ripple current and long life rating such as PANASONIC FM or FC series.
Please post back what you find.
Please leave rating if it helps.

SOURCE: I was watching tv and

Tries tv unplug,replug it back like about an hour later,by for the tv resetting itself back for factory setting.Now tv should be working,if still have the same problems.The tv have power supply board problems and causes.That the board,where the power a/c cord plug into it.Tries website like Ebay.com to buy a refurbish power supply board for the replacement.