I will try to help you with this question.
The issue you describe is consistent with an inverter board not working.
Unfortunately there is nothing you can do from outside the set,via customer adjustments to correct this issue.The TV will need to be serviced by a professional.
Now,based on the models,this inverter circuit board may or may not be available as a replacement.Sometime they are considered part of the LCD panel,and this whole LCD panel will need to be replaced(very expensive !)
Sometimes,based on the panel type used inside,the inverter board still can be replaced,even though there is no Hitachi part# XXXXX it,just by trying to get the generic part# XXXXX it.
If this inverter board is available,it will cost around-$100-$130,based on the tv model#.
Add another $100 as labor fee,and the total repair cost can be as high as -$250.
Now if the tv is less than 1 year old ,it will still be covered by manufacturer warranty,and Hitachi will fix it for you at no charge.
I hope this will help you to get an idea about what is going on with this tv set.If you need more info about this issue,please provide the model# XXXXX I will gladly help you!
Thank you and Happy Holidays!