I need to know how to unlock the parental lock on my daughter's Spongebob television model number sb305

There are different types of locks, one is a straight lock and others include parental control, most require a password and the original remote.

Not knowing brand or model number etc that is as much as I can tell you.

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

Most TVs have a parental control lock that can be set to prevent children from watching specific television shows. In order to activate or deactivate the controls, you need to know the four digit security code or parental lock control password. If you forget the number you chose or if the lock gets set accidentally, it is still possible to unlock the TV.
Instructions

Turn on the TV and grab the remote. In most cases, you will need the original remote to unlock the TV if you aren't sure of the unlock code. If you don't have the original remote, you will need to purchase one.

Look at the screen. If you see a blank screen with a red key on the bottom of the screen, press 'Function' and 'Mute' at the same time. This should unlock the channel. This is an option for people who want the TV to stay locked but, want to be able to bypass the lock to watch a certain show or channel. All other channels will remain locked and the TV will fully lock when it is turned off.

Unlock all of the channels on the TV by entering the factory reset code. There are three main reset codes that TV manufacturers set. These are 0711, 6688 and 3308. Try each one until you find the one that works. This will reset the TV to original factory settings. When you do this, you will loose any information that you have stored in the TV, such as favorite channels, automatic timers and the clock. You will have to go through the full initial set up.

Call the technical support service number in your owner's manual if none of those codes work. A technician can help you troubleshoot the television because the problem may not be the locking control. When you call, make sure that you have the model number and serial number of the TV.

Take your television to a TV repair shop. In some cases, a professional who access to wiring diagrams for your television set may have to rewire certain components in order for the television to unlock. This is usually the case when the TV locks by itself while it is on.

Omni TVs have a child lock that allows parents to prevent children from watching specific channels or television shows with certain ratings. To activate or deactivate the controls, you need the four digit pass code. If you forget the pass code or if the lock gets set accidentally, you can still unlock the TV.
• Use the original Omni remote control to turn on the TV. You need the original remote to bypass the child lock. A universal remote won't work.
Check the screen. If you see a blank screen with a red key on it, press the "Function" and "Mute" buttons at the same time. This unlocks only the channel that is on the TV. All the 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 "6688," which is the factory reset code. This code resets the TV to original factory settings. Once this is done, you will have to go through the initial setup.

• Call Omni technical support at (416) 260-0047. A technician can help you troubleshoot the television as the problem may not be the child lock. You'll need to know the model number and serial number of the TV.
•Take your television to a TV repair shop if you are still unable to unlock the TV. The problem may be with the wiring, so the repairman may have to rewire the TV

Most TVs have a parental control lock that can be set to prevent children from watching specific television shows. In order to activate or deactivate the controls, you need to know the four digit security code or parental lock control password. If you forget the number you chose or if the lock gets set accidentally, it is still possible to unlock the TV.
Instructions

Turn on the TV and grab the remote. In most cases, you will need the original remote to unlock the TV if you aren't sure of the unlock code. If you don't have the original remote, you will need to purchase one.

Look at the screen. If you see a blank screen with a red key on the bottom of the screen, press 'Function' and 'Mute' at the same time. This should unlock the channel. This is an option for people who want the TV to stay locked but, want to be able to bypass the lock to watch a certain show or channel. All other channels will remain locked and the TV will fully lock when it is turned off.

Unlock all of the channels on the TV by entering the factory reset code. There are three main reset codes that TV manufacturers set. These are 0711, 6688 and 3308. Try each one until you find the one that works. This will reset the TV to original factory settings. When you do this, you will loose any information that you have stored in the TV, such as favorite channels, automatic timers and the clock. You will have to go through the full initial set up.

Call the technical support service number in your owner's manual if none of those codes work. A technician can help you troubleshoot the television because the problem may not be the locking control. When you call, make sure that you have the model number and serial number of the TV.

Take your television to a TV repair shop. In some cases, a professional who access to wiring diagrams for your television set may have to rewire certain components in order for the television to unlock. This is usually the case when the TV locks by itself while it is on.

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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

Could be anything,not possible,only tries reset every setting.Ask Emerson for how to unlock.Go to their website might show how to reset codes.

A model number for your Magnavox TV would be helpful because the Parental Control Reset procedure varies. There should be a sticker on the back of the TV showing the model number. If you have a newer LCD model, the unlock code is usually 0711. Ignore any "Incorrect" warning and enter 0711 again. Then set or clear the Parental Access Code.

Look for a button cell battery, from what I've seen they're common in small CRT television sets.