[mythtv-users] Horizontal lines with NVidia TVout

Fedor Pikus fpikus at gmail.com
Mon Jun 27 00:53:04 UTC 2005

On 6/26/05, SÚrgio Gaspar <smmg at nukitel.com> wrote:
> Try pluging your myth box, TV set and AV system all to the same wall socket.

PC is UPSed, plugging TV and the amp into the same UPS did not help.
Tivo is also on the same UPS and there are no lines there.

> If this doesn't solve your problem then it's probably a ground loop caused
> by your cable provider.

Bingo! Disconnect coax from wall - perfect picture. Connect coax -
lines start scrolling. I guess Tivo is not affected because it does
not have its own ground, it has a two-wire plug (so do TV and amp).
I'll have to figure out a way to tie the coax shield to the ground. I
hope something blows up at the cableco when I do and they fix their
floating ground :)


> > Typically, a slow rolling band comes from a 60 Hz (or 50 depending on
> > your localation in the world) AC source.  Check for proper ground
> > (ground loops will cause this).
> >
> > # Endaf
> >
> > Stuart Morgan wrote:
> >
> >>On Sun 26 June 2005 21:16, Fedor Pikus wrote:
> >>
> >>
> >>>I've had my Myth box connected to a CRT and a small Toshiba TV (NVidia
> >>>composite TV-out), and had excellent picture on both. Now I moved it
> >>>to my AV system and connected it to a 32" Toshiba TV (CRT), I tried
> >>>SVideo and Component out, and I always get the same problem: light and
> >>>dark horizontal lines or bands slowly drifting up the screen, one or
> >>>two lines at a time. Very visible when picture is dark, very annoying.
> >>>It is not really specific to Myth: I see these lines on Fedora login
> >>>screen, on my window manager screen after I log in, and in Myth
> >>>everywhere. Interlacing options in Myth don't seem to help at all (and
> >>>of course they would have no effect before Myth starts). The other
> >>>problem I'm seeing is pretty strong pincussion distortion: left edge
> >>>of the screen bends inwards. Increasing overscan helps with the
> >>>distortion, to a degree, but the scrolling lines are unaffected. Any
> >>>suggestions?
> >>>
> >>>
> >>
> >>Sound to me like interference - particularly magnetic. You haven't just
> >> stuck
> >>two huge speakers next to the TV have you? Or failing that is there
> >> anything
> >>with a strong EM field nearby (Microwave, electric motor or spacial
> >> anomaly)?
> >>
> >>
> >
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> >
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Fedor G Pikus (fpikus at gmail.com)

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