My TV has a white/gray screen when I turn it on. I get nothing else, no sound either.

SOURCE: sharp lc-19sb225u tv turns on with a "white noise"

The blue screen means the processor of the tv no longer finishes the loading of the firmware - hardware fault, either the chip that stores the firmware or the processor have failed.
Since the chips are soldered on the mainboard and cannot be removed separately that means that the entire mainboard will have to be replaced. This is it
http://www.partstore.com/Part/Sharp/Sharp/LC19SB25U/Sharp/Sharp/DUNTKE352FM02/New.aspx
Now you must decide if it's worth paying $400 for a replacement board or it's better just to buy a new tv - i'm for the second option.

SOURCE: there is sound, but screen is in gray,black and

Hello,

Problem is in either power supply or the Y-Sustain board.

The Y-Sustain is a relatively large board out of which go connections to the side of the display; it's therefore closer to either the left or the right side of the display, has at least one rather large heat sink on it and fat power cables connecting it to the main power supply.

Often there are fuses on that board - one or more. Check those.

if they are blown you can try to replace them, but expect them to blow again - usually the whole board needs to be replaced.

I hope this will help to solve the problem....