@sugamama bad power capacitors on the power supply can cause that. However, there are plenty of other things that can do the same. You got to start somewhere, so you might as well remove the back (unplug your TV) and take a look (don't touch) on the power supply.
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Check for domed, leaking caps. Post some images with our question so we can see what you see. Use this guide [guide|21499|for that.]