May a pop noise, now no picture but has sound. it is a Hitachi 42 in. plasma tv mod. 42edt41a

WARF135 I am sorry chap but you obviously do not know what you are talking about and I must point this out to you. PLASMA tvs do not have inverters or lamps in them! need to be careful as some people will follow the advice they are given here and we must be careful not to misinform. Well thanks for reading this. (by the way solution # 2 is probably correct)

I would say that your Y SUSTAIN board has failed, Take the back of your tv and look on the left hand side, Your board will have a fuse on it that should be short, (blown) if this is the case then it confirms the y sustain board will need replacing, Get the part number of the board and Google or Ebay for a replacement.
The big ic (IMP) under the heatsink overheats with time and pops, A common fault for many plasma TV'S
Hope this helps

Sounds like the Invertor for the backlights has blown. if you are lucky and it is just the invertor blown it could cost £50-£150 for a new invertor board, but if you are unlucky then the backlights themselfs have blown too which means the TV is beyond economic repair.