logik lcd tv

[Dee-M-See]

I am having problems with my 14" LCD tv the model number is LCX14LN1
It is operated through a transformer reducing the voltage to 12volts. However each time i switch it on it takes about ten minutes to get going, as soon as it is switched on the picture comes and so does the sound,but then the sound disappears and the picture goes hazy then after about ten minutes the set appears to operate normally, Can anyone tell me whether the problem is with transformer or the set itself?