Panasonic TH-50PX70EA HAS A HALF SCREEN PERFECT BUT OTHER HALF IS LINED AND CHANGES COLOUR AND SOMETIMES GOES BLACK GETS CLOSE TO PERFECT THEN GOES LINED AGAIN PS sorry for caps

Bad panel, not repairable

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/
Line, faults & possible causes to LCD screen are given with illustrations. You can get an idea about the fault to an extent.

Check the left connector from the Tcon to the panel, if its ok replace the board

The set uses two boards to drive the screen --one for each half or side.

Different names are used like sustain or in LCD sets inverter.

From your description it sounds like your power supply if faulty. You can get parts for this TV at www.interliquidparts.com

I had the same issue. I am going to replace my scan buffer boards. The upper half of mine works but the lower half is black so I would replace the lower Scan buffer board but in case of future issues I have ordered both upper and lower for $44.
The scan buffer boards are fairly simple to locate. Open up back of tv there are two biffer boards identical. The item or product code on them contain letters either SU or SD (Scan up and Scan down)Look up tv parts and item code you will find a place to order or just get the 1 800 number from tv manufacturer.

my panasonic th-58pz800u well not even come on no blinking lights at all

NEED REPLACED SU BOARD Manufacturer Panasonic Part Number TXNSU1HNTU Description PC BOARD

satelliteand cable TV is only comes in black and white.
this a HTML type plug or a coaxial
select menu and source
very weird... should default to colour

if no luck try plugging in a desk top digital box tune using that

TH-42PX20 TH-50PX20 Operating Instructions High Definition Plasma ...

ftp://ftp.panasonic.com/television/om/th-42px20_en_om.pdf

turns on and off by itself