Try connecting a video source to the input shown on the screen and turning it on before you turn on the TV. This is NOT a work-around, it's for diagnosis - it provides something to look at besides the input name and the default blank screen. Look for a dark, flickering or pink-tinted band across the set. These indicate a bad Cold Cathode Fluorescent Lamp (a dark band could also be a failed inverter).
Unless all of the inverters light up their lamps successfully within a couple of seconds, the set is designed to shut down to prevent secondary damage caused by trying to run a malfunctioning high voltage circuit.
CCFL lamps can be replaced, but unless you are very skilled at soldering electronic components, you should pay extra to get lamps with the wires already attached, if they are available for your model. See the Tech Support page at LCDParts.net for more information.
You said you replaced the panel, by which I assume you mean the LCD unit, and I assume it was because of this problem. If that is not correct, please clarify. Did it come with the lamp tubes installed (i. e., you had to connect the pink and white wires to the inverter)? If the on-screen display does show the input name, we know the lamp and inverter for that part of the screen starts up, or you would not be able to see it. That doesn't tell us anything else about the other CCFL tubes.
Another possible cause of the problem is a bad capacitor in the power supply. Given that you have no audio, but you do see the input name on the screen, I would guess it's in a section that provides between 12 and 24 Volts (the 5V standby and run supplies need to work to get the input name on the screen, and the 180 V supply needs to work to get the inverters to start up).
If you trace the circuit back from the output to the transformer, you will find the components in this order: filter output capacitor (a plastic cylinder marked with the size in µF and voltage 25V or 35V), coil (a cylindrical copper coil sometimes covered in black heat-shrink tubing, or sometimes toroid shaped), filter input capacitor, diode. On the circuit board, the capacitors will be marked with "C" followed by a schematic identifying number, the coil will likewise be labeled with "L" and a number, and the diode with "D" and a number. Usually the filter input capacitor is the first part to fail, and when it does, the output voltage is about half of what it should be. Bad electrolytic capacitors sometimes have a bulging top, discolored plastic wrapper, or chemical leakage. It is possible to have more than one failing capacitor at a time, so if you see several that look bad, change them. When you select a replacement, it should be the same µF, the same or higher voltage rating, same or higher maximum temperature rating, and it should be a type rated for high frequency and high ripple current. The part usually costs less than $2. On my 37" LVM-27W1, the capacitors in question would be 1000µF 16V (12V output) and 1000µF 25V (18V and 20V outputs).
CAUTION: the big capacitors on the end where the wires from the power cord are connected could be charged to line voltage even when the set is unplugged. The power input area is clearly marked on the circuit board with a heavy black line. Don't touch anything on that side of the line unless you know what you are doing and why. Some parts on electronic circuit boards (transistors and integrated circuits) can be damaged by static electricity discharge from your body. Avoid touching the circuitry unless you first discharge your fingers to circuit ground (look for circuit metal surrounding the screw holes that would be connected to the metal frame of the TV when the board is installed). Handle circuit boards only by the edges.
I found your second comment after I posted my reply to the first. The next step is to check the power supply (I would have done that before changing the LCD unless the LCD had visible physical damage).
Did the set work well for a while after you replaced the panel, or did it come up with this problem immediately? If it worked for a while, we can continue looking at the power supply. On my model, the power supply is a Delta DPS-336AP. Look for a similar marking on the circuit board. I strongly recommend checking the supply output voltages before replacing the unit - if they are all correct, the power supply is probably working properly. It isn't easy to get at the voltages - you may have to connect the common lead of the meter or oscilloscope to the chassis and attach a small pin or fine wire to the lead to get it down into the pockets of the power supply connector - a standard probe tip is too large. The voltages are marked on the board next to each connector.
If the problem came up immediately, check all of the connectors removed for panel replacement to make sure they are properly seated.
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I just replaced the panel, it does light up briefly but I can not see the image or hear any audio.
I tried that and the source doe not show, and their is no audio. I had just replaced the panel, but this issue existed before I replaced it.
yes there was another issue with the lcd panel. when this unit comes on it does light up. is there a part number for the power supply board? the caps all look good..
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