how to fix ?

You need a sighal source. It can be an antena, a satelite dish or a cable box.
Make sure that you have one connected. If it's a cable box, it also need to be turned on.
Also, does your uncle still have the user manual?

Electro
April 2016

"when he switches it on the red light keeps going off"

As far as In know, that is normal behaviour for most TVs. When the TV is "off" (on standby) there is a pilot light showing, which goes off when the TV comes out of standby.

Would you like to be a little more forthcoming with your fault description.

Assume we have absolutely no idea what you are on about. Because we don't until you tell us.

XXX
April 2016