I have a hp plasma TV 55 about 9 years old there are red dots all over screen in the dark areas. Is the TV shot or can it be repaired?

If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/
Faults & possible causes to LCD screen are given with illustrations. You can get an idea about the fault to an extent.

Usually either the main board or the power board--if set is 6 months old---no warranty?

Probably not a circuit board problem but rather an overheated display. Perhaps the TV is mounted ttoo close to the wall or has just worn out. Not usually a repairable problem.

I had the same problem a few months after buying the TV, called LG and they sent a tech to replace two boards in the tv. No further problems since.

Panel is bad. Contact Samsung to see if they will replace the panel.

This is know as diffusion. You will need to locate the Vs adjustment inside the TV and vary it up and down by NO MORE THAN 10 volts. If this does not correct the problem then you will need to replace the Plasma panel.

red and green dots on screen

This is called diffusion, it is caused when the power supply voltages do not match what the plasma panel requires. Unfortunantly this is not something you should do yourself, high voltage danger and possible damage to the tv if you are not very experienced with this repair. A technician can however read the voltages and adjust them to specifications and this will get rid of the dreaded red dot diffusion. Very common in samsungs but not that expensive of a repair. Hope this helps.

I have the same tv - change the power supply. Corne Bronkhorst

The driver board is going bad it sounds like and if you do not call up and get it fixed under warranty, as it should still be under a warranty, then its going to be a nice hefty repair bill. Good Luck Ps Please dont forget to rate this thread