Hi i am a north american warranty tec,your tv has a failing picture tube,happens more on other brands than sony usually,the cathodes,red green blue are out of balance causing akb system fail,the only repair is to adjust the g2 and have htr resistors lowered in value this will restore a like new picture in most of these tv sets for about 2 years until total crt fail. The g2 adjust will in most cases stop the flashing and restore the picture,the resistor change will stabilize the colour output if necessary,also reducing rgb cut off in service mode will add another year or so to tv lifetime. Both repairs are lethal if you dont know what you are doing,the voltages on these boards will kill if handled,so authorized servicepersons only should attempt this one,we have restored around 90 or so various brands including your one in the last year alone for this type of problem. Also have soldering redone on hv and related circuits while it is being serviced.(a real tv tech will know exactly what I am mumbling about) Your power supply is working perfectly as is the rest of your tv.