HOW DO I FIND THE PARENTAL CODE THAT MAY ALREADY BE ESTABLISHED. TV IS SECONDHAND AND I CANNOT DEACTIVATE THE CHANNELS THAT ARE PROGRAMMED IN AS A BLOCKED CHANNEL.

It sounds that your TV is locked by someway. Just unlock it. Proceed the following.
Many Jensen TVs have a parental lock that can be set to stop children from watching certain television shows or channels. In order to activate or deactivate the controls, you have to know the four-digit code or parental lock passcode. If you forget the passcode or if the lock gets set accidentally, you can still unlock the TV.

• Turn on the TV using the remote control. In most cases, you will need the original Jensen remote to unlock the TV if you aren't sure of the unlock code. You can purchase an original replacement online if necessary.

• Look at the screen. If you see a red key on the bottom of the screen, press "Function" and "Mute" on the remote at the same time. This will unlock the channel. Do this if you want to bypass the lock to watch a certain show or channel while leaving the TV locked. All other channels will remain locked and the TV will lock again when it is turned off.

• Unlock all of the channels on the TV by entering 0711 or 3308. These are the Jensen factory reset codes that will reset the TV to the original factory settings. By doing this, you will loose any information that you have stored in the TV, such as channel labels and schedules. You will have to program the TV again by going through the entire initial set up.

•Call the technical support service number in your owner's manual if neither of those codes work. A technician can help you troubleshoot the television as the problem may not be the parental lock feature. Have the model number and serial number of the TV available when you call.
• Take your television to a TV repair shop if neither of the codes work and the TV locked by itself while it was turned on. In this case, the TV may need to be rewired.

Many Jensen TVs have a parental lock that can be set to stop children from watching certain television shows or channels. In order to activate or deactivate the controls, you have to know the four-digit code or parental lock passcode. If you forget the passcode or if the lock gets set accidentally, you can still unlock the TV.

Turn on the TV using the remote control. In most cases, you will need the original Jensen remote to unlock the TV if you aren't sure of the unlock code. You can purchase an original replacement online if necessary.

• Look at the screen. If you see a red key on the bottom of the screen, press "Function" and "Mute" on the remote at the same time. This will unlock the channel. Do this if you want to bypass the lock to watch a certain show or channel while leaving the TV locked. All other channels will remain locked and the TV will lock again when it is turned off.

• Unlock all of the channels on the TV by entering 0711 or 3308. These are the Jensen factory reset codes that will reset the TV to the original factory settings. By doing this, you will loose any information that you have stored in the TV, such as channel labels and schedules. You will have to program the TV again by going through the entire initial set up.

•Call the technical support service number in your owner's manual if neither of those codes work. A technician can help you troubleshoot the television as the problem may not be the parental lock feature. Have the model number and serial number of the TV available when you call.
• Take your television to a TV repair shop if neither of the codes work and the TV locked by itself while it was turned on. In this case, the TV may need to be rewired

Apex TVs have parental locks that allow you to block certain programs based on
their rating. When this feature is no longer needed and you want your TV to display all programming no matter its rating, you must unlock your TV. Unlocking your Apex TV is done completely from your remote control and does not require any tools. The process takes less than 5 minutes.
• Press the "Menu" button on the remote control and use the arrow buttons to scroll down to the "Parental Guide" option, then press the "Enter" button.
Type in the default parental code "6688" if you have not set your own code. If you have set your own code, type it in. If you set your own code and forgot it, override it by using "6688."
Use the arrow keys to switch the parental lock to "OFF." This allows all programs to be viewed no matter the rating. Press the "Exit" button on the remote and start watching all your channels.

Apex TVs have parental locks that allow you to block certain programs based on
their rating. When this feature is no longer needed and you want your TV to display all programming no matter its rating, you must unlock your TV. Unlocking your Apex TV is done completely from your remote control and does not require any tools. The process takes less than 5 minutes.
• Press the "Menu" button on the remote control and use the arrow buttons to scroll down to the "Parental Guide" option, then press the "Enter" button.
Type in the default parental code "6688" if you have not set your own code. If you have set your own code, type it in. If you set your own code and forgot it, override it by using "6688."
Use the arrow keys to switch the parental lock to "OFF." This allows all programs to be viewed no matter the rating. Press the "Exit" button on the remote and start watching all your channels.

This is what I found in the instruction manual on this and I posted it here for you. Try using 3355 for the code and everything else listed here. If that doesn't work, try the very last tip which tells you how to do a factory reset and repeat the first step using the 3355 as the code.

Here's the instructions from manual:

Parental Control
Parental Control allows you to block certain channels or programs so children cannot view
programs that are not age appropriate.
To enter the Parental Control menu, you need an
access code. The first time you enter, use access
code 3355. See "Setting an Access Code" on
page 33 for information on creating a new access
code.
You can set the following options to block
content:
• Channel Lock — Blocks selected channels
• Movie Rating — Blocks movies based on their rating (G, PG, PG-13, R, NC-17, and X)
• TV Ratings — Blocks TV shows based on their rating
• Block Options — Turns on or off all your parental control settings
NOTE: You can use Clear All to unblock the channels and programs that you have set.
NOTE: If the Block Control in the Parental Control menu is enabled, all the sub screens in POP (POP1,
POP3 and POP12) mode will be blank



Setting an Access Code m
After you enter the Parental Control menu for the first time, you can set your own four-digit access
code. If for any reason you lose or forget your access code, you can use the default code.
1 In the Parental Control menu, select Change Code.
2 Using the number pad on the remote control, enter a new access code.
3 Select Exit.




Reset the original factory defaults. Press Menu on the remote
control, select Setup, and then select Factory Reset

hello The parental control menu enables
you to limit access to programs that
may contain objectionable material
or are not suitable for viewing by
children. The default access code is
0711
may contain objectionable material
or are not suitable for viewing by
children. The default access code is
0711.
The following table provides details
about the menu items:
Component Function Range / Options
Lock Enable Enables the parental control lock. When
enabled, channels with objectionable viewing
content are blocked and can only be
accessed with a password. You can block
channels according to the movie or TV ratings
of the channel’s programs.
Off, On
Movie Rating Helps you block programs based on their
movie ratings. See “Movie Rating” on
page 25 for more details.
–
TV Rating Helps you block programs based on their TV
ratings. See “TV Rating” on page 26.
–
Change Code Changes the password for the parental control
lock.
Press the number keys to
change the password.
Reset Resets all channels and programs to their
default factory settings.
–

regards
shaun
Parental Control Menu
Lock Enable
Change Code
Reset
Back
Main Menu
Picture
Sound
Size
PIP/PBP
Parental Control
Channel Setup
Setup
Exit
Press Right to Enter
Press Right to Enter
Press Right to Enter
Press New Code
Off On
TV Rating
Movie

get on the menu on the parents classification and deactivate

You may have solved the problem by now, but if you go into the menu and choose V Chip rating, then TV Rating. All the choices should say [VIEW]

Here is the download for the model you listed. I on page 36 is how to reset the code. I'd keep the manual out of your kids hands. ;-)).

http://tv.rca.com/RCATV/Assets/pdfs/27F520T_1641312E_IB_e-06.pdf

Child Lock

Combos--Should have original remote. Press and hold the power button for 6 to 10 seconds


Combo Model T25208, V-Chip Forgotten Password
If you forget your password, simultaneously press VOLUME down on the TV/VCR front panel and the 0 number button on the remote for a few seconds. This resets the password and you can enter a new one.

Combo Model 13TVR62, V-Chip Forgotten Password
If you forget your password, press STOP/EJECT on the TV/VCR front panel and MENU on the remote simultaneously. This resets the password, but not the limits you’ve set.
Televisions with Parental Lock Feature


If you forgot your password for this feature, press the following buttons on the remote, one at a time. (Note: You must be in the password entry screen) Press, Mute, Display,Clear and Reset, this unlocks parental controls and you can now re-enter a new password.
OR TRY THIS..
Press and hold Menu on the TV AND volume down on the remote for 3 seconds. Nothing will appear on the screen, and the Parental Controls will unlock, and you can re-enter a new password with the LOCK PARENTAL CONTROLS

CTC169AU
Channels that have been locked can be viewed only when the PARENTAL CTRL function is set to OFF. This can only be done with the remote control-it can not be changed with the buttons on the front of the TV.

Therefore, after you turn on PARENTAL CTRL, you simply hide the remote control so that your children can not watch the locked channels. The locked-out channels will remain unviewable even if the TV is unplugged or the channels are autoprogrammed again. The only way to view locked channels is to use the supplied remote control to set the PARENTAL CTRL function to OFF.

The PARENTAL CTRL and the CHAN CTRL functions work hand-in-hand. The instructions below will first tell you how to turn parental control on or off with the PARENTAL CTRL function and then how to lock desired channels with the CHAN CTRL function.
1. Repeatedly press MENU to select SETUP MENU, and then press + or - to display setup functions. Repeatedly press MENU to select the PARENTAL CTRL function. . When this function is set to ON, PARENTAL CTRL is activated and any channels you locked with the CHAN CTRL function will not be viewable. . When this function is set to OFF, PARENTAL CTRL is deactivated and all channels are viewable.

2. To lock channels, press the MENU button to select the CHAN CTRL function. Select a channel you want to lock by pressing CHANNEL up or down. Then press +. The CHAN CTRL setting will change from NORMAL to LOCKED when that channel is locked. To return the channel to NORMAL, press the - button. Repeat step 2 for each channel you want to lock. If the PARENTAL CTRL function is set to ON while you are locking out channels, each channel will go blank as you lock it. When the PARENTAL CTRL function is set to ON and a channel which has been locked out is tuned, the TV will display the words PARENTAL CONTROL to let your kids know you have locked it.

CTC185's
If the front panel function buttons don't work, (menu, ch up/dn etc.) but the functions work normal with the remote, enter the "Channel" menu with the remote and turn "Parental Control" off.

CTC203's
In the event you have forgotten your password, perform the following procedure:
Press and hold for 3 seconds the TV button on the remote while pressing the menu button on the TV.
This procedure will turn off the parental lock and erase the previous password .

Another Possibility To Try For Various Models: If TV's in the Parental mode and askes for a password that's forgotten, Press menu on the TV, select Parental Lock #4 on menu, then with the remote press Mute, Display, Clear, and Reset buttons in sequence.

TX808 Chassis
If Parental Controls have been set and you don't know the password, do this:
Press and hold the volume down and the channel up buttons at the same time for 5 seconds.
Now you can reset the password to 0000, and using that password you can now access the V-Chip menus.

TV's (Made by Daewoo or possibly Apex, ie. GE model 24GP653)
The factory default pass code of 6688 is also the override code, in case the owner forgets their pass code. If that doesn't work, another place in the owners manual says to push Function and Mute on the remote at the same time. Function is the top right button.