[mythtv-users] HD-PVR horizontal bands

[Christopher Meredith]

On Wed, Nov 17, 2010 at 7:56 PM, john blue <rwc at bestpond.com> wrote:
> On Thu, 18 Nov 2010 08:53:42 am Christopher Meredith wrote:
>> On Wed, Nov 17, 2010 at 3:31 PM, Brian Wood <beww at beww.org> wrote:
>> > On Wednesday, November 17, 2010 02:08:31 pm Christopher Meredith wrote:
>> > > > Yeah, you can get magnetic ferrules for the cables, but if your
>> > > > hdpvr came with the same cables mine did (the 5 wire joined
>> > > > cable), it is very high quality (at least mine is)...
>> > >
>> > > Yeah, that's the one I'm using. I wonder what the problem is, then...
>> >
>> > The problem is not cable quality, it's most likely common mode AC hum.
>> >
>> > Try re-orienting your cabling, especially if you are crossing AC power
>> > wiring.
>> >
>> > Make sure all of your gear is connected to the same AC power outlet (as
>> > much as possible).
>> >
>> > Make sure all your gear is grounded or, conversely, don't use grounds
>> > except for the protective grounds in the power wiring.
>> >
>> > A fairly good explanation of ground loops is here:
>> >
>> > http://en.wikipedia.org/wiki/Ground_loop_(electricity)<http://en.wikipedi
>> > a.org/wiki/Ground_loop_%28electricity%29>
>>
>> In my case, the HD-PVR sits directly beside the STB and the component cable
>> goes directly from one to the other. The excess is coiled and bound with a
>> twist tie. Everything is plugged into a single power strip which is plugged
>> into a single outlet. Come to think of it, I actually have a second power
>> strip plugged into the first (I know, I know).
>
> Christopher, this may be a useless idea , but is relatively cheap to try.  Could I suggest you make your cable 'untidy'
> and try just uncoiling the excess, to see if that helps the problem. I have had problems with some cables that were a
> bit long and were coiled. Using a shorter cable of straightening up the cable usually sovled any issue. However, I have
> not had a similar issue to yours.
>
>>
>> I do have the monitor output from the HD-PVR connected directly to the TV.
>> I can't imagine how that could be causing it but I'll mention it anyway.


I'd like to resurrect this discussion (history here:
http://bit.ly/k9brVY ) because I have a little more info. To recap,
anything recorded with my HD-PVR has thick, horizontal bars of
discoloration running up the screen. I have tried different cables to
no avail. This is the new information:

1. I have a video clip showing the behavior here:
http://www.youtube.com/watch?v=1oiNXsJVd_0 . It's most easily seen in
the first scene on the wall behind the characters.

2. Most of the previous replies had to do with group loops and AC hum,
but I have noticed that when watching on the TV through the HD-PVR
passthrough (i.e. NOT recorded content) I do not see the lines. This,
even though there is a second cable through which the signal must go
when watching this way. That suggests to me that the artifacts are not
in the signal when it gets to the HD-PVR.

3. I recently had my HD-PVR RMA replaced. The old one was a C2
revision, the new one is an F2. I am still noticing the behavior on
the new box.

Does this information help any? Could it still be AC hum even though
it does not show up on the TV, despite the signal being routed through
the HD-PVR? Thanks!
http://www.youtube.com/watch?v=1oiNXsJVd_0