Unfortunately, it's impossible to diagnose the cause of failure from those symptoms as the TV will go into protection mode and cycle on/off (LED blinking) in many different fault conditions.
However, it can often be due to the failure of a single 'minor' component (eg. faulty capacitor or short circuit diode) and is not necessarily a sign of an expensive repair. Although that is possible too, eg. if for instance a transformer has failed.
So, if you take to a repair agent, ask for an estimate.
Cobweb, November 2007