Television and Home Theater

i did a self diagnostic check on my toshiba 51h83 and came up with this code - NG QA152 Does anyone have an idea what this means?

hello this is first time trying to repair a plasma tv i was givin a 42" grundig planatron plasma display.but there is a small fault somewhere i fix pcs by day so started bit of trouble shooting any help or advice would be greatly appreciated
1.plasma appears to power up okay takes a few seconds then light goes from red to green and you get a menu appearing (i think its to select languages or input) but then after that it disapeers and you are leftwith a bank screen the plasma does not display any picture but still seems to be recieveing power!

I have an eight year old Zenith TV connected to a dish - the set seems to work fine but the picture has become dimmer over time - letters, such as the channel number and other info that is displayed white on a black background, is somewhat fuzzy - so, my question is, is it time for a new TV or is there something that can be done with this set that is cost effective? Thanks for your help, Dave