Purity Problems

[lucerne20]

I put up a thread a month ago with the problems I have had trying to get a 28" widescreen television. I have given up now and decide to save my money for a LCD or Plasma screen I have resorted to a Philips 25" 4:3 Television with no bells and whistles.

Now what I don't understand is why this set intermittently shows the same problems, usually on BBC 1, as all the previous 12 widescreen tv's in some way. It is most noticeable when the BBC show their red background with what programmes are on that evening. On the right side of the screen there is _sometimes_ a pink patch with a yellow patch on the left, never the other way round though.

People have said it is speakers near the TV, there aren't any now except for the ones built in. However, the purity problem comes and goes. If it was the speakers that I had near the set from the surround sound system then, correct me if I incorrect, but the purity fault would be there all the time?? Or maybe the other suggestion (from a man at the BBC) that our neighbour has a piece of medical equipment that is causing the problem, all they have is one of those automatic beds!

If anyone can help I would appreciate it.

Andy

[Tight Git]

This is a strange one!

What you describe is certainly a purity problem and, as we know, purity problems are caused by magnetic objects too near the set.

The puzzle is why it comes and goes.

I can only suggest that you see what happens if the TV is used in a different part of the room (or preferably in another room).

Incidentally, I assume that you mean it comes and goes whilst you watch.

If you mean that it's ok at switch on but gets worse after a while, then that's much easier to explain!

Please let us know how you get on.

[lucerne20]

Unfortunately I have tried the sets in different parts of the room, most along one wall, but the current set we tried on the opposite corner entirely with much the same result, even to the point of only connecting the sat receiver.

(At one point I thought it may be some interference from that so I took the one from the bedroom to no avail)

Last night whilst my son was watching cbbc (Clifford etc) I noticed the pink patch move whilst my neighbour was reversing their car off the driveway! But that evening whilst watching BBC1 the patches had gone and the set hadn't been turned off for the degaussing to work.....

After a lot of sets doing the same sort of thing I am beginning to believe one of the tv engineers who said it was something about the location.

The only thing that has changed whilst all this has been going on is that the electricity company installed a new main fuse and meter, surely that can't affect it?

[Tight Git]

Originally Posted by lucerne20

I am beginning to believe one of the tv engineers who said it was something about the location.

"Location, location, location".

I always thought that was Estate Agents!

Well, if you've had the same problem with other sets, that would seem to be the answer.

Perhaps someone else has an idea.

The only solution that comes to mind is to move house!

[GaryB]

Purity problem can come from any ferrous metal - I've had to degauss a few radiators in my time. It can even come from magnetic rock. The current trend for converting old industrial buildings into flats has also caused a few problems. Most of them contain steel RSJs which also become magnetised over time.

If you're in a Semi-Detached or terraced house a speaker on the other side of the wall can do it.

[Tight Git]

Gary B,

Agree with everything you say, but why is the purity problem coming and going?

That's the puzzle!

[GaryB]

Why it changed with the car is a complete mystery. The usual reason for varying purity is a detached shadowmask. This is the fine stell mesh just behind the front face of the tube. It's usually held firmly in place but can become detached, usually if the set has been dropped or otherwise abused. If this has happened you can sometimes hear it pinging slightly if you put an ear near the set. If it is detached, you will also usually find that the purity varies if you tap the front face of the tube.

As several sets have been tried, none of this will apply here though and, as you say, it will remain a puzzle.

[lucerne20]

Maybe a daft question but how you degauss a radiator then?

[GaryB]

Originally Posted by lucerne20

Maybe a daft question but how you degauss a radiator then?

Using the same type of degaussing coil that you use to manually degauss a TV. Something like this would do the job but a bigger version makes the job easier. You switch it on, wave it all over the radiator and gradually walk away, waving it as you go. Then switch it off.

[lucerne20]

Many thanks, I think the audio department at work have one of these. I'll give it a go, all else has failed........

[GaryB]

Just a thought. If you do suspect something in or around the house, try walking around with a compass. That should show if there is anything magnetic in the area.

[lucerne20]

many thanks to all, some things I need to try.

ps. how do you close a thread off?

[Tight Git]

I think you just edit your first post so the title reads "Solved:xxxx".

But please don't leave us all up in the air wondering what the solution is!

[GaryB]

Especially why the purity changed when the neighbour was reversing his car. I've been in this trade for 20 years and I've never heard anything like that before!

[lucerne20]

Dont know why it changed with the Neighbours car, but before trying the degauss wand which arrived yesterday I thought I would give the compass a whirl. Lo and behold the pointer moved the completely opposite way, from pointing at north at the back of the house to directly at the radiator. Gave the wand a wave but to no avail, the radiator was exactly the same magnet as when I started.... I think it must of been my eyes wanting it to move. So in a nutshell I have magnetic radiators in 4 of the 6 rooms in the house........ Some plumbing to be done I think, or save up and go plasma..... Thanks again to all that gave advice.