51 philips yellow streak

It depends on what the problem actually is; are the streaks colors like red or blue outlines around lettering etc?

The more you tell me the better I can help. I will post a photo or two of what convergence problems look like.
This set is also prone to another problem, on a blank video input look at the screen: you should only see Video 1 (etc) and if you see faint curved lines (red, green or blue) and or the back ground is also wrong color you have the second problem.

let me know which it is.. If this information helped you rate this solution as very helpful as I do this here for free.

SD TECH

Sounds like the CRT tubes are going out which is fairly common on Sony. Inside the back of the TV there are 6 knobs - 2 for each color...one is for focus - dont touch - the other for brightness...turn down the brightness just a hair untill the lines go away.

Get a convergence kit from www.TvRepairKits.com

move any magnetic sources from by the tv (ie speakers)

Sounds like the convergence IC's went south.  

The TV is in factory or demo mode - turn tv off and unplug it from wall outlet for 30 seconds - turn tv back on after 30 seconds and see if problem goes away. If not, press the (volume -) and (channel -) buttons repeatedly for about 10 seconds to see if "C" will go away. If this fails call 1-888-PHILIPS for further assistance (they do Magnavox also).

The screen probably needs to be degaussed, which will require either a degausser or a technician. Try turning the television off, and then unplugging it from the wall outlet. Then replug after 30 seconds and turn it back on. Also, try plugging any cables from a cable or satellite box into another set of in-ports on the back. If the problem persists, the screen needs to be degaussed.

sounds like you need to do convergence.

Probable bad blue CRT and if blue goes bad guess what might
happen to the red and green.........T.

I had the same problem with mine 2 years ago (TV was 1.5 years old at that time) I had extended warranty on TV and it was fixed by Sony at no cost to me. Now yesterday I have another problem with it. All of a sudden screen went BLUE. No Sound either. It could be the CRT (That's what I read here) Out of luck this time. Will call local Repair shop (70 miles away) and see how much it will cost to fix it. Good luck.