My apex tv has a blue screen with a red lock key on the left side

SOURCE: unlock apex tv model # AT2702

• If you have a blank screen with a red key on the bottom left, simply press the (function or F) button and the mute button at the same time. This will unlock the screen and allow you to view the channel as desired.
  
  
• If your TV asks for a 4-digit code or password please enter 3308 or 6688 to unlock the screen or reset any preset rating levels.
  
  
• If you have a GT2011J or GT2011S Television, hold the (Display) button for 10 seconds, it will unlock the screen. If password or code is requested, try 3308 or 6688.

SOURCE: unlock apex tv model # AT2702

try this manual;

[PDF] AT M C T
On the remote try pressing the ( F ) button and the mute button at the same time on your remote control.
Here's the link for the 2402s manual:

http://www.retrevo.com/search/v2/jsp/downloadPage.jsp?doc=4db1185db9d3369 Pass Code Menu
This menu allows you to change the access code for the Parental Guide
functions of the TV set. Pressing the “Menu” key when Pass Code
Control is highlighted. This will turn on or off the Pass Code function. With
the Pass Code function ON, you can also change the Pass Code. Use
the down arrow key to highlight “Pass Code,” then enter the new Pass
Code using the numeric keypad. Press the left arrow key when finished.
1. The factory default pass code of 6688 is also the override code, in case
you forget your new pass code.
2. The factory defaults have TV-MA and MPAA-X ratings blocked . Hope this may help you

DON'T FORGET TO RATE:

SOURCE: Apex TV locked out picture

• If you have a blank screen with a red key on the bottom left, simply press the (function or F) button and the mute button at the same time. This will unlock the screen and allow you to view the channel as desired.
  
  
• If your TV asks for a 4-digit code or password please enter 3308 or 6688 to unlock the screen or reset any preset rating levels.
  
  
• If you have a GT2011J or GT2011S Television, hold the (Display) button for 10 seconds, it will unlock the screen. If password or code is requested, try 3308 or 6688.

SOURCE: my apex tv is locked.

You have to hold the button that looks like a flag (top left) and press either the mute or video button. I don't remember which one 

SOURCE: APEX tv model #AT1302 My tv screen is black with a

child lock is active. Unlock press function and then mute on remote. only way to do it.