RE: [OT ish] PAL/RGB TV problem

["Keith Doxey" <ukha@xxxxxxx>]

Hi Paul,

The problem is caused by the TV detecting a voltage on Pin16 of the SCART
which indicated RGB mode. Different TV manufacturers impliment SCARt
switching in their own preferred style.

Some TV's will only allow RGB signal into the TV if Pin 8 is also active
and
displaying that input on the TV. Because the Digibox is permanently on then
boththe pins will be active and the TV is allowing the RGB signals to
directly drive the tube. However, because you have selected the TV's own
tuner to view terrestrial TV you are getting the audio and video from that
but the RGB signals are overriding the output of the colur decoder in the
TV. The sync pulses from the Digibox are not getting through so it is
trying
to lock the picture to the sync of the terrestrial video. The vertical sync
timing of the two is slightly different so the picture is rolloing and
scrolling.

RGB will give you the best picture quality from the Digibox but you need to
put it on standby when not in use.

One thing you can try IF your TV allows you to manually select an RGB input
( I have a 25"JVC and a 14" portable that ONLY allow RGB to be
selected by
SCART Pin 16) is to disconnect Pin16 of the SCART. If the TV is correctly
switching RGB signals via the SCART input then the problem will go away but
I did once have a Philips TV that would display an RGB over the top of
teletext even if Pin16 wasnt active. The only way for me to read teletext
was to turn my BBC B Computer off before I looked at text.

It thats as clear as mud and you are going to Hatfield I will explain it in
person :-)

Keith

www.diyha.co.uk
www.kat5.tv


> -----Original Message-----
> From: Paul Robinson [mailto:ukcueman@xxxxxxx]
> Sent: 12 May 2003 16:50
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] [OT ish] PAL/RGB TV problem
>
>
> A friend has just bought a Thomson digibox for viewing the
> FreeView stuff.
>
> When connected to his TV via both RF and Scart leads,
> changing the TV to
> view analogue stuff via the RF lead produced the correct
> audio but with a
> very dodgy picture. It would show the channel being shown by
> the digibox,
> but very dark and unstable in that it would be constantly
> moving right, as
> if it had lost "horizontal hold". So it was showing the
digibox video
> regardless of which analogue channel was selected on the TV,
> but the audio
> was the correct analgoue audio channel.
>
> Apart from these symptoms, everything worked as expected.
> Connecting an LCD
> TV produced a perfect picture with none of these problems.
>
> After much playing, I fixed the symptoms by changing the
> digibox so that it
> used "PAL" instead of "RGB".
>
> What would it mean if the digibox uses PAL? Does anybody
> understand what
> this means the problem was? Is there a better solution?
>
> Thanks,
> Paul
>
>
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