Samsung LE32R73BDX/XEU Dimming

[cossie]

Hi,
     This is my first post and first TV repair. My sons 32" Samsung LE32R73BDX will work great for about 40 minutes but will then gradually dim till you cannot make out a picture. Can someone diagnose which part I need to get on order please.
Also it fails to turn on first time, it recycles then turns on the second time but we can live with that.

Thanks