Just bought a second hand philips 20hf5474 with universal remote but no user manuel. cannot get into menu to set channels, clock etc

Check this link to download the user manual.

I just bought the same TV second-hand and had the same problem. Solution: Use remote to change channel to 00. You can't display channel 00 using front panel - a remote is required. I have a very basic RCA universal remote, & it does the trick.

Somewhere in it's lifetime, a user has set the 'user preference' to 'mute' while this channel was active. I don't know your specific set, but most TV's need a remote to work 'mute'.
Second hand set?
[A] check all buttons on TV for a crossed-out speaker symbol, or
[B] buy a universal remote and select pin for your set. Then,
Try these:
ZENITH - 000,001,004,023,038,058,059,064,073,121,135,136,153

To get all the functions you need, a universal remote will not do - you need to get the OEM remote for the unit OR a remote for another unit manufactured around the same time since they usually employ similar frequencies and have similar functions.

http://www.remotecodelist.com/remotes/magnavox/Philips-Magnavox_PM525S.pdf
Thisis the user's manual for a Phillips remote control. There is a list ofcodes in it. They should be rather universal. There's also instructionsas to how to program it. I believe that there is a way to program itwithout using the codes.

Programming with Code Search

1. Manually turn on the device (TV, VCR, etc.) to be controlled.

2. Press and hold Code Search button until the red indicator stays on. Release the Code Search button.

3. Press and release the desired mode button (TV, VCR, etc.). The red indicator blink, then stays lit.

4.Press the Channel Up button repeatedly (up to 300 times) until thedevice could be controlled changes channel. The red indicator blinks,then stays lit. If you accidentally overshoot the code required, pressthe Channel Down button to backtrack through the library until thedevice changes channel. Pressing Channel Up changes direction toforward again. Press and release the Mute button to install the code.

Hope this helps :)

http://www.remotecodelist.com/remotes/magnavox/Philips-Magnavox_PM525S.pdf
This is the user's manual for a Phillips remote control. There is a list of codes in it. They should be rather universal. There's also instructions as to how to program it. I believe that there is a way to program it without using the codes.

Programming with Code Search

1. Manually turn on the device (TV, VCR, etc.) to be controlled.

2. Press and hold Code Search button until the red indicator stays on. Release the Code Search button.

3. Press and release the desired mode button (TV, VCR, etc.). The red indicator blink, then stays lit.

4. Press the Channel Up button repeatedly (up to 300 times) until the device could be controlled changes channel. The red indicator blinks, then stays lit. If you accidentally overshoot the code required, press the Channel Down button to backtrack through the library until the device changes channel. Pressing Channel Up changes direction to forward again. Press and release the Mute button to install the code.

Hope this helps :)

1. Manually turn on the device (TV, VCR, etc.) to be controlled.

2. Press and hold the CODE SEARCH button until the red indicator stays on, then release the CODE SEARCH button.

3. Press and quickly release the desired mode button (TV, VCR, etc.). The red indicator blinks off once.

4. Press the CHANNEL UP button repeatedly (up to 300 times) until the device to be controlled changes channel. The red indicator blinks off with each button press. If you accidentally overshoot the code required, press the CHANNEL DOWN button to backtrack through the library until the device changes channel. Pressing CHANNEL UP changes the direction to forward again.

5. Press and release MUTE to install the code.

http://www.remotecodelist.com/remotes/magnavox/Philips-Magnavox_PM525S.pdf
This is the user's manual for a Phillips remote control. There is a list of codes in it. They should be rather universal. There's also instructions as to how to program it. I believe that there is a way to program it without using the codes.

Programming with Code Search

1. Manually turn on the device (TV, VCR, etc.) to be controlled.

2. Press and hold Code Search button until the red indicator stays on. Release the Code Search button.

3. Press and release the desired mode button (TV, VCR, etc.). The red indicator blink, then stays lit.

4. Press the Channel Up button repeatedly (up to 300 times) until the device could be controlled changes channel. The red indicator blinks, then stays lit. If you accidentally overshoot the code required, press the Channel Down button to backtrack through the library until the device changes channel. Pressing Channel Up changes direction to forward again. Press and release the Mute button to install the code.

Hope this helps :)

http://www.remotecodelist.com/remotes/magnavox/Philips-Magnavox_PM525S.pdf
This is the user's manual for a Phillips remote control. There is a list of codes in it. They should be rather universal. There's also instructions as to how to program it. I believe that there is a way to program it without using the codes.

Programming with Code Search

1. Manually turn on the device (TV, VCR, etc.) to be controlled.

2. Press and hold Code Search button until the red indicator stays on. Release the Code Search button.

3. Press and release the desired mode button (TV, VCR, etc.). The red indicator blink, then stays lit.

4. Press the Channel Up button repeatedly (up to 300 times) until the device could be controlled changes channel. The red indicator blinks, then stays lit. If you accidentally overshoot the code required, press the Channel Down button to backtrack through the library until the device changes channel. Pressing Channel Up changes direction to forward again. Press and release the Mute button to install the code.

Hope this helps :)

Universal remotes are limited. Power, volume, channel and mute is often all you can get to work. Others buttons such as menu and source and video and antenna and CC (closed caption) will not work with any universal remote. I always recommend the original to my customers.
The original can be bought here:
http://www.replacementremotes.com/store/index.cfm