Cost to replace plasma on Sansui 42 inch TV

The main power supply regulator section circuit fault. Either it will be a separate board, or the part of main 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. Pull up older posts.
http://electronicshelponline.blogspot.com/
It will be best to replace the power supply regulator board as card basis rather than making "Surgery" to it; which usually will make loss for both money and time. Even though you can make it right, it will cost around an amount equal to the cost of a new board; including the cost of (spare parts + service charge) More to say, most of the spare parts to it will be difficult to get from open electronic spare part market. This is true to most of the flat panel TV power supply boards; irrespective of its brand and screen size.

Tcon board faulty / Check the link to know more about tcon board problems.
http://electro-medical.blogspot.com/

It will cost around 80% of the total cost of a new Sansui 50" Plasma Tv.

How long? My old plasma took several seconds to come up before it died.

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I have sansui television 42"model number STY0342, plasma 3D.when l turn it on sometimes it takes time to switch on after turning it on.it will change the standby light to blue.what might be the problem.

No--this is called a PDP or plasma display panel and no two (even same brand) can be interchanged.

The cost of a Panel exceeds the cost of a new set--broken screen=fatal issue.

Tries websites like Shopjimmy.com,Ebay.com to buy the refurbish Tuner board.

howto get the hdmi signal thro hdmi to dvi cable in plasma pdp42 sansui tv in dvi input

You don't have any magnet anywhere near the TV do you ?
If not it sounds like something magnetic is interferring with the picture.

If not get the warranty out :D