Have flat screen tv has sound no picture

Fred, Unplug for a couple hours then try, if does not reset, board,capacitors or power supply gone bad.
Check the attached links for TV's problem.,
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Fix Your TV Instantly

how to fix 42 RCA flat screen

RCA 276046 Power Supply Unit PSU Boards Replacement Guide for RCA LCD TV...

http://v6.tvrepairtips.org/anon/supertips?page=1&make=&model=LTV46W1%20HD&problem=

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electro-medical.blogspot.com/
http://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

The T con board is faulty. It is the board with flat ribbon cables going to the bottom of the screen. It is not hard to replace this board. You can get one from here:
TV Parts Universal TV Stands DLP Chips ShopJimmy

This is an exact problem that I am facing with my Seiki 50" TV. From my research, here are the probable issues:
1. Main Board/T-Con Boards are fine
2. Power Board : MIP550D-5TB could be defective - most probably the culprit. There is a power test to try but w/o schematics, it is not possible to identify component
3. If Power Board replacement does not solve, it is the backlight LED strips that are defective - tought one to replace.
Will update this thread at a later date.

The board that controls the picture is in the middle of the screen when you remove the back of the TV. It has 2 flat ribbon connectors going down to the bottom of the screen. Make sure all the voltages on the power supply board are present, then take off the metal cover to expose the board. Look for obvious burnt parts. Sniff the board to see if there is a burnt smell. If there is then go to
TV Parts Universal TV Stands DLP Chips ShopJimmy to get the replacement board.

Ur tv the LCD inverter board it dead.This board it help to get a backlight to ur LCD screen panel go through the Tuner board to produre a picture.Replaced this LCD inverter board u will get ur picture back.Tries websites like Shopjimmy.com,Ebay.com to buy a refurbish LCD inverter board for the replacement.It a long board in shape.

In most cases with flat screen TVs, the power supply for the screen has failed. Most commonly the Backlight Inverter Board or related power supply board. Best to have a Tv repair shop look at it and tell you which board when bad. Then, determine if it cost too much for the shop to replace the bad board for you.
If you want to replace the board yourself, you can find a replacement board on the internet by running a search by the part number on the board.

If the TV is still under warranty, definitely go that route.

When the TV is on, need to check the back light is on(go back side & look into through)

If the back light is on -- need to exchange the Main Board
no back light -- exchange the Power Board --- 95%
exchange the LCD panel --- 5%(inverter)

on your remote control click menue and than select sound and go from there

LCD TV TroubleshootingThe defective LCD TV may have the following common symptoms:

Symptom: No picture on screen but LCD TV still has sound.
Solutions: The problem is cause by defective inverter. Replacing ivnerter will solve hte problem. Symptom: Screen flash on and off between 1/2 to a few seconds, but power indicate light stays on and TV still has sound.
Solutions: The problem is cause by defective inverter. Symptom: Blue Screen but no picture
Solutions: The problem is cause by defective Main Board(AD Board). In some cases, this problem may cause by the defective Screen Controller board. Thsi board is mounting on teh back of LCD TV Scree. Symptom: Power light stays on but no display and sound
Solutions: The problem is cause by defective Main Board(AD Board) or Power supply board. Symptom: No Power or Power indicate light does not lits
Solutions: The problem could cause either by defective Power supply board or defective Main Board(AD Board). Symptom: Screen is half dim and half bright
Solutions: The problem is cause by defective LCD Panel.It needs to be replace.

This is a power supply problem. Try to check the fuses ,fusable resistor ,capacitor and transistor in power supply board.

Hope it may help you;

Regards,
VOTIT