Sorry to go off air and miss your reply.
The model number of my tv is tx26lmd70 which I have had for five years with no problems. The problem has occurred in the last three months.
I am connected by my Sky HDset top box aerial and hub. Also there is a set top box DVD player. I do not have this problem with other devices in the day.
I switch on usually in the morning and the picture arrives then some seconds later picture and sound vanish for a little while after which both return perfectly then both switching return again some minutes later, this annoyance continues with less frequency many times as time passes. A lot later the set performs perfectly.
If the set is turned on after being switched off during the day the whole process often starts again.
set working well at this moment will try again tomorrow morning to see if "menu" etc. works.
Intermittent electronic faults the very devil!
I switched on at 10:15 got the sky box on at 10:17 after setting up - 10:18 everything ok.
Blank picture and sound at 10:20 for 1 second no time to press menu.
From then the sound only was interrupted for one second at 10:23, 10:24, 10:24:30 an;later at 10:34, 1035 .......
blank picture and sound at 10:30 lost briefly - returning to perfect vision afterwards.
Apart from the losses the TV is perfect and useable. I feel you have been most helpful and patient and we have not got to the bottom of my problem. Unless you can continue, I feel we have covered most aspects and there is little point in continuing.