Hello, I've got this Vizio 42" that has a loud buzzing sound and sounds like it's comming from the transformers T-701 and T-702. The backlight caps right by the connectors CN-203 seem a little discolored which or C-743 and C-764 but other than that everything looks ok. No bulged caps or burn marks. Any ideas ?

KB

I don't know much about flat screen TVs, but here are a few tips I found while browsing the support community website for Insignia, the house brand for TVs sold by Best Buy.

A buzzing sound from the power supply area, especially near the power transformer, is almost certainly indicative of an overload somewhere in the set. In fact, in the days of tube-type TVs, this was an unmistakable symptom of power supply overload; if it is left unchecked in either type of TV, however, it could severely damage the set.

If your TV is still under warranty, I'd return it to the store from which you purchased it for exchange or repair. If not, and the set is more than a year or two old, I'd junk it and get a new one. Flat screen TVs, particularly those with screens 19 inches or smaller, are often not worth repairing when they develop problems as the cost of repairs, including the often hefty diagnostics charges made by most TV repair shops, at least those that will repair flat screens, could and often do exceed the price of a brand-new set.

If the backlight capacitors are even slightly discolored, they could be going bad and should be replaced. Capacitors that are obviously bulging, at the top or elsewhere, are definitely defective and must be replaced immediately.

Those sets suffer from backlight transformer failure. Also, not on the main power supply but on one (or two if the set has them) of the backlight modules, if they are separate, you will find bulged capacitors. Also, look under the backlight modules and you may see dark marks under one of the transormers. This means the transformer is failing. I have managed to get backlight modules fairly reasonable on our "favorite" auction sight. They are a common failure.
Is the picture bright, no flickering at all?

Those sets suffer from backlight transformer failure. Also, not on the main power supply but on one (or two if the set has them) of the backlight modules, if they are separate, you will find bulged capacitors. Also, look under the backlight modules and you may see dark marks under one of the transormers. This means the transformer is failing. I have managed to get backlight modules fairly reasonable on our "favorite" auction sight. They are a common failure.
Is the picture bright, no flickering at all?

Thanks Jeffhs that helps and no bulging caps on this thing at all but that did help.

Zenith26kc20 I'm in Baton Rouge and noticed you are in N.O. so thats cool.

This isn't my set but I'm an old tube guitar tech working on a buds TV.
He said the set sometimes when turned on lights the LED on but nothing comes on. Other times it comes on and works for awhile but starts buzzing and then dims down and shuts off. Sounds like backlights to me but not sure. No burn marks on the transformers or discolorization except for the two backlight caps by the connectors which are two small blue ceramic looking caps.

Can you post a picture of the backlight modules?

Can you post a picture of the backlight modules?

I'll see if I can get co-worker to bring them all. All I have is the main pcb board.

http://i420.photobucket.com/albums/pp283/kbullion/c18585ee-ed56-4fec-91d7-37a47059bb6e.jpg (http://s420.photobucket.com/user/kbullion/media/c18585ee-ed56-4fec-91d7-37a47059bb6e.jpg.html)

http://i420.photobucket.com/albums/pp283/kbullion/87cdff54-7aa7-4704-b09a-2b1e84553afc.jpg (http://s420.photobucket.com/user/kbullion/media/87cdff54-7aa7-4704-b09a-2b1e84553afc.jpg.html)

Anybody ?

Sorry, those look like the backlights themselves. The inverter has some small
(1 inch by 3 inch) transformers that are flat on them. Look around the board that they are on for dark spots, especially under transistors.

http://i420.photobucket.com/albums/pp283/kbullion/20130808_074920.jpg (http://s420.photobucket.com/user/kbullion/media/20130808_074920.jpg.html)

http://i420.photobucket.com/albums/pp283/kbullion/20130808_074822.jpg (http://s420.photobucket.com/user/kbullion/media/20130808_074822.jpg.html)

There are no burn marks on the transistors behind this photo at all or anywhere else on this board.

Chect the three capacitors on the left for leakage. They look overheated. These little blu caps are a continual source of trouble. If they get warm when running that is a dead giveaway.