What could be causing this interference?

aranj · 19-12-2006, 23:39

I'd be grateful if anyone would take a look at this photo I took of the interference on my really old TV. Vertical bands to left and ghosting/shadowing. It's always done it to a certain extent but is getting worse. Or am I just getting fussier in my old age?

Nothing to do with my ntl box or my dvd recorder as the TV has the same left-hand-side interference when switched on without digibox, dvd recorder or even external aerial plugged in. I.e. no cables at all plugged in (apart from power!), switch tv to AV to display black screen instead of "snow" and you can still see the interference.

It is not the tv as the (equally rubbish but not quite so old) portable displays the same problem.

My electricity supply is causing this???

Thanks in advance for any ideas.

keithwalton · 20-12-2006, 00:01

the ghosting seems to be an effect of a magnetic field, is there anything with a magnet to it to the right of the screen.

If its an old crt it could just be the tube on its way out / loosing alignment

punky · 20-12-2006, 01:13

That's normally caused by magnets... Do you have speakers close to that side of the screen?

aranj · 20-12-2006, 07:16

Thanks for the replies. Well the left-hand speaker is about 1.5 metres away, and the right about 2 metres. Moving the left speaker as far away as it will go (about 3 metres) seems to have no effect, or is the damage already done so to speak?

I have the TV on a wooden cabinet, with the DVD/hard drive recorder underneath on a shelf, and the Pace digibox underneath that.

We also have an "antiference" signal booster plugged in for the analogue reception (which is necessary with our awful signal - and works well).

The whole lot is plugged into a power strip (but not a surge protecting one) but again moving the TV onto it's own power outlet doesn't improve matters.

Thanks.

handyman · 20-12-2006, 09:32

Have a butchers at this page on the bbc site.

http://www.bbc.co.uk/reception/analo...rference.shtml

r1ch · 20-12-2006, 09:48

The ghosting looks like it might be due to transmission line reflection problems caused by using a cable of the wrong impedence. Assuming that you're using an RF connection between your source and the tv, is it a 50 ohm cable? If you've used satellite cable instead (which is 75 Ohm) that could be causing the problem.

aranj · 20-12-2006, 11:35

Thanks for the replies, and for the BBC links. Am reading a few factsheets now.

I don't think it can be anything to do with the cables.
I used the RF cables that came in the box with my Panasonic DMREX75 DVD Recorder. Okay, the SCARTS are old and presumably cheap as they came free with a VCR ages ago.

BUT if I remove all the cables from my TV set (SCART and RF), switch it on and press the AV button (to make it black screen instead of "snow") I still see the vertical bars to the left hand side.

r1ch · 20-12-2006, 12:18

In that case I think that it's likely to be a problem with the TV itself. It seems unlikely that it would be external interference or a magnetic influence because you are getting ghosting of items within the picture. Magnetic fields generally warp things on a screen rather than causing them to repeat and external interference adds noise but again wouldn't normally cause the effects that you are seeing. I'd say that it looks like some kind of impedance mismatch or 'ringing' in a signal amplifier but the problem is almost certainly internal to the TV.

Wicked_and_Crazy · 20-12-2006, 13:45

Its not magnetic fields at all. Most TV's are sheilded appart from in front which is obvious.

That looks to me like ringing and will be an internal fault to the TV

aranj · 20-12-2006, 14:00

Thanks all. It may be an old rubbish tv but I didn't particularly want to replace it just yet - I have two toddlers in the house! Looks like I might have to now though. Thanks again.

Wicked_and_Crazy · 20-12-2006, 14:02

I dont think you will get a new tv for 2 toddlers

aranj · 20-12-2006, 15:06

Quote:

Originally Posted by Wicked_and_Crazy

I dont think you will get a new tv for 2 toddlers

Maybe I could put them on ebaBy?

Nikesh · 20-12-2006, 15:15

Quote:

Originally Posted by aranj

Maybe I could put them on ebaBy?

LOL

07-01-2007, 12:36

My old television has this, but it's very faint, and does not go though the whole pictures, it only has about an inch of it to the left of the screen ( NO speakers near it or magnets).