Tv automatically powers off by itself within seconds.

The most common reasons for the TV to turn on by itself is having foreign matter around the power button of the remote control, external devices connected to the TV, and your settings. If the power button is stuck, clean the remote control.

I would try a factory reset. If the router is physically powering itself off chances are you have defective router.

More than likely, the power supply portion of the TV is going or gone.

It is an indication that you have a problem on the power supply on the main board.
Nowadays tv will automatically shuts off if there was a problem on the power supply.
It is quite technical so if you are not an expert I've advice you to send it to a repair shop or look for a qualified technician to isolate the faulty parts on the low voltage power supply and do re-soldering on some dry joints on the main boart because sometimes dry joints affect the performance of the regulated power supply...

Thanks for using fixya...

If it is not a bad soldering joint somewhere, it could be the mode switch. They can sometimes be cleaned with Servisol Video 40, but you might have to replace it.

1. Might have a power supply issue take the back off and see if there are any bulging caps on the power supply board. If you dont know what your doing call a tv service tech.

I had a similar problem with my Phillips 42 in. LCD HD TV.

Here's the problem. The Power Supply Board. I opened my TV up(warranty was up of course) and found several bad capacitors. Phillips and several other companies were sold capacitors that although were highly rated failed within 5 years because of a lack of preservatives. All sorts of electronic equipment is now being effected due to these defective capacitors.
Solutions?
1. Take it in and have it fixed
2. Open it up, check the board for faulty capacitors(bulged or leaking) Buy a new Power supply board and install it.
3. Remove PSB, remove faulty capacitors and replace with compatible new ones.

Hope this helps

just had this tv fixed for this exact problem-it cost 577 bucks to fix- some sort of control panel that had corroded

happened with my 2002 42" model. they say the convergence circuit.