Sony TV model KDL-40V4100. What could cause a snowy white screen?

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. 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/ In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.
Before going further; try a hard reset first. If it does not help you, replace the main digital board. There are two methods to reset TVs. The first is simple to do; a Hard Reset. The other is somewhat skilled; is a Factory Reset (System Reset). To make it a hard reset, just unplug the TV from AC mains wall socket, and re-plug it back after 15 minutes or so. If you do this by overnight is better. This procedure will make it a hard reset. If you want to make it a system reset [Factory Reset]; you have to enter its service mode option, and select the factory reset option. If you wish to get some details; visit the site linked here. .

T'Con board fault. If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/
Faults & possible causes to LCD screen are given with illustrations. You can get an idea about the fault to an extent.

Sony Bravia KDL-40V4100 models have a problem with the screen going blank, faded or washed out ( negative ghosting) . It is caused by a bad chip on the T-con board. A replacement chip is available from shopjimmy.com (Sony 55.40T02.C08 T-Con Board Component Repair Kit) for $14.95- If your not an excellent solderer, send your board to them for a repair $69.95.

If you wish to get some details; visit the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/
Line faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent. Faults to all LCD & Plasma screen are similar, irrespective of its brand and screen size.
Search the site by type in the "BRAND NAME" of your device; (Exclude the model number), in the "Search box at the top right of the display window of the Homepage" to get gathered related posts.

It could be something like an ETC-inverter board, or the power board. I have the same TV with a cracked screen. Are you interested in selling yours?

Could be the power board or main board defective, but I suggest you do firmware update first. Go to http://esupport.sony.com/US/perl/swu-list.pl?mdl=KDL42V4100&LOC=3#div_pos_30 download the software.

I'd say about the blinking to a black screen would be your cable provider. As for the stripes that means that your board panels can be going bad, you can try updating the firmware of the TV to help but if that doesn't work you're getting very close to full failure on the TV.

turn cc on receiver

Probably the main board. This has a 1 year mfc parts and lobor warr. I would contact Sony for the nearest auth servicer. If you open it you will void the warranty.

ACTUALLY WITHOUT SEEING YOUR PROBLEM PHYSICALLY I CANN'T SAY ANY THINK, BUT FOR YOUR KNOWLEDGE LET ME TELL YOU NO TV MAKES ANY KIND OF SOUND DURING SHUT OFF. & you are saying for more than 30sec, i think you should call the SONY TECHNICIAN for visit.