There's a few things you can try.
Sounds like what you need is to reset to factory default if possible(unless the set is actually damaged).

On most magnavox's this will get you into the service mode.

Using the power button on the tv (not the remote), turn the tv on, then off , then back on again.
Now the tv is on for the second time, now you use the remote punch in these numbers in this order
0, 6, 2, 5, 9, 6 then hit menu button.
Then channels will change as you hit the numbers but when you hit the menu at the end it should enter service mode. Check your service choices and try to find the default settings.(note: this works with most but not all magnavox)

The only other thing I could sugjest is, supposedly if you unplug a magnavox for 4hours or more it will reset to factory default.

best of luck chris