[mythtv-users] My TV doesnt like input from computers

Shanon Mulley shanonmulleyster at gmail.com
Sun Jun 4 09:14:30 UTC 2006

ok. That sounds like its worth a try.

So how do I find out what frequency to use? I have tried googling it,
but found nothing. Do I just try frequencies at random? Should I put a
range in, or a single number?

On 6/3/06, Chris <gchris at bellsouth.net> wrote:
> > Thanks for the reply - I have only just been in a position to give
> > this a try (2 months later...).
> >
> > And... no go. Turning the brightness right down does nothing. It is identical.
> >
> > Does anyone else have any ideas?
> >
> > On 4/11/06, Marco Nelissen <marcone at xs4all.nl> wrote:
> >> >I have a bit of a weird problem with my TV. When it takes input from a
> >> >computer, the image is never quite right. It seems (for lack of better
> >> >words to describe it), that the horizontal stretch is off. That is,
> >> >the image pulls away from the sides of the tv (left and right), to
> >> >leave a few cm (sometimes more then 5cm) of black space on either
> >> >side. This gap isnt consistant either - it varies depending on the
> >> >brightness of the image being shown. And if the brightness varies for
> >> >the current image (say the top is bright, and the bottom is dark), the
> >> >gap at the sides varies to.
> >>
> >> I've seen this with many CRTs, even computer monitors, or TVs with
> >> non-computer images. It's certainly not something that's specific
> >> to feeding a computer signal to a TV.
> >> Basically, the horizontal deflection voltage isn't stable and being
> >> influenced by picture brightness. It could be that the signal you're
> >> providing is simply too bright for the powersupply to supply adequate
> >> voltage to all its sub-circuits. Try reducing the brightness and see
> >> if the problem goes away or is reduced to acceptable levels. If not,
> >> your TV's power supply may need to be repaired. If you don't want to
> >> spend the money on repair, you could try making the problem less
> >> obvious by dialing up the image size until the gap is no longer
> >> visible.
> If this condition (called "blooming" in TV parlance) is visible ONLY
> when the picture is generated by the computer, the problem is very
> likely to be that you've set the horizontal refresh frequency
> incorrectly (either too high or too low) in your modeline.  The high
> voltage needed to operate the CRT is developed by the horizontal
> deflection circuits which are "tuned" to operate within a narrow band of
> frequencies.  If you are at the edge of that band, or outside it, the
> CRT's high voltage will go out of regulation causing just the effect you
> described.  It's not good for the TV's deflection circuits (may cause
> overheating) and if the CRT voltage gets too high it may cause the CRT
> to emit xrays so it's not a good idea to live with it.
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