A couple of months ago I had problems getting a decent picture on one of my televisions, the one located in my living-room. The television is a pretty new set (less than 2 years old) and is an LCD unit from a 'good' maker; it had worked well in another location, but I seemed to have trouble getting a reliable, decent-quality picture. The unit I had there before (a conventional, but now obsolete CRT unit) had given a perfectly good picture. I traced that to a defective TV-antenna socket in an intermediate VCR/DVD-player, which was little used, but needed to be powered-on to feed the signal to the TV. I dumped the VCR/DVD player, as I had another DVD player in reserve (and rarely watch video-cassettes any more). In addition I replaced the SCART cable from the DVR unit in that room with an HDMI cable to connect to the TV, so that only the DVD player is connected to the TV using a SCART cable. Perfect, stable picture in all modes.
Now in another room, my dining-room/kitchen, I have another LCD TV (less than a year old, also of a 'good' make), to replace an equally-obsolete CRT unit. I replaced all my televisions last year with LCD units to prepare for digital switch-over in this area (which I wrote about some months ago). Prior to my departure to Spain for a few weeks last November the new television performed well, but ever since I returned home it has been performing poorly on an intermittent basis. I had assumed it was a defective unit that needed replacing (preferably under the guarantee), but I had been too lethargic to take definite action as it did perform OK some of the time. In the last week, however, it had begun to 'play up' more and more and earlier this evening the picture was breaking up persistently, so even I was spurred into action! Yesterday I went so far as to do research on-line on TVs I could replace it with. In the interim, this afternoon I thought I would replace it temporarily with another very new LCD unit from one of the bedrooms, which I brought through ready to do the switch. Of course I had to move the stand the TV sits on and, lo and behold, the picture became perfect. I think the problem was a loose SCART cable and the general jumble of wires behind the stand (for various items of equipment) causing interference. I think I may have cracked the problem! I'm also releived to know that the television itself is probably functioning perfectly normally. I won't 'count my chickens' too soon, however - assuming it's working well, consistently, over the next few days then I think it safe to assume the problem is solved.
Moral - the importance of ensuring cabling (even shielded SCART and HDMI cables) are fully connected and don't overlap too much with power cables.