No picture...Sound is fine.

Vertical scan output section circuit should be checked. Contact any service technician.

Fault with the main power supply regulator board. Check and replace damaged component/s at its main power regulator [SMPS] section circuit. Contact any service technician. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/

Might have been a power spike that flashed channel memory. try rescanning for channels. And make sure physically that you antennas wiring is good and anywhere on it. post what you find good luck...

that silver box is called TV tuner (see picture ) ............ but in your case that is not the problem ......... after 4 or 5 yrs (depending on usuage ) in some TVs on mainboard & CRT tube's circuit board at some soldering joints cracks develops ... then due to loose contact TV behaves as you have described ........ when you are hitting that lightly on its side then these cracks at soldering joints are getting connected temporarly & for few seconds or minutes you are getting normal picture ....... so solution is most of the soldering joints on mainboard & on CRT circuit board has to be resoldered ....... only good tv service engineer can do this without shorting joints or damaging components..... so that silver box ( TV tuner ) is not the problem because when it gets deffective then you will get picture that comes when tv is switched on ---- usually it will be blue screen ......& also if you connect dvd you will get picture normally ...only thing is that you won't get picture from cable or antenna ..............

I ran into this problem with a VIZIO TV. I had to change the main display board. It is the board that all the components hook up to (example HDMI, coaxial cable, any input to the TV will be on this board) . Hope this helps you

RGB is a computer connection input.

take to a service station i think just changing the displsy IC would do . but check in service centre

Did you mean the picture is collapsed only in the middle horizontally(white line appears on the middle part of the screen)?
If that is the case, maybe vertical IC failed or loose connection.

turn off your CC or closed caption

1.Check audio/video RCA jack cables
2.check S-video(if you use S-video cables)
3.check with another dvd player to get normal picture on your tv system. if picture is normal in this process. then problem with your old dvd player.
4.if same problem occurs in other dvd player. then problem with your television. external audio/video processing circuits
5.if the tv is ok. then the problem with your old Dvd player audio.video converting circuits
6. if can be rectified by authorised service engineers
7.Contact service engineer. as there is no recitification process from user part