Interference on plasma?

tomsch · #1 11-24-2005, 11:23 PM

just got my first Plasma and the picture quality is very good with the HD channels and the DVD playback - but I have noticed a 3-inch bar moving from the bottom of the screen upwards in slow tempo (and then repeating it) - it is especially noticeable when the picture is all in one color (like a black screen or a screen full of green grass - wherever the bar moves the color takes on a very slight purple-ish tint.
The problem doesn't always occur.

I have a Panasonic ProLine 42-inch plasma - my cables in the back are somewhat organized, but they are in some proximity to the power cables - also all power cables share pretty much one outlet - the speakers used for the home theater are magnetically shielded.

Any advice?

Thanks!

mtrycrafts · #2 11-25-2005, 12:17 AM

Quote:

Originally Posted by tomsch

just got my first Plasma and the picture quality is very good with the HD channels and the DVD playback - but I have noticed a 3-inch bar moving from the bottom of the screen upwards in slow tempo (and then repeating it) - it is especially noticeable when the picture is all in one color (like a black screen or a screen full of green grass - wherever the bar moves the color takes on a very slight purple-ish tint.
The problem doesn't always occur.

I have a Panasonic ProLine 42-inch plasma - my cables in the back are somewhat organized, but they are in some proximity to the power cables - also all power cables share pretty much one outlet - the speakers used for the home theater are magnetically shielded.

Any advice?

Thanks!

Firstly, move the power cables away from any signal cables in the vicinity as a starter and see if it comes back. Has this issue come up on the previous TV?

tomsch · #3 11-25-2005, 03:44 AM

I played around some more: the horizontal bar is actually about 1 foot wide, where the bottom 4 inches or so of the bar are somewhat darker in color - overall it's a green bar - I can see it clearly on our CBS HD feed that comes through the Comcast cable box as CBS shows its HD picture with grey bars on either side - on which I can see the green bar slowly scrolling up very clearly.

And here the interesting bit: when I connect my cable box (or my DVD players) straight into the plasma via component, I don't get those green bars.

When I go through the receiver (Onkyo TX-SR503) I get the bars - I even unplugged all other connections (except the speaker cables) to see if another component or audio cable was causing this - but no difference.

So again, when I go straight into the TV, the picture is flawless
when I go via the receiver I get the bars - what's up with that? is that normal because the signal goes through another piece of equipment?

Eric Apple · #4 11-25-2005, 01:47 PM

Except for the intermittent part (that would be unusual for a ground loop), sounds like ground loop noise. Even though you are using the same plug for all equipment, the cable feed is tapped to ground at a different point.

You could try a ground loop isolater on the cable feed - http://www.*****************/pe/show...number=180-075

Edit: that url is for p arts e xpress.

tomsch · #5 11-25-2005, 03:01 PM

but I do get the same problem when viewing a DVD - could it be that my receiver has a different ground? would experimenting with different outlets make any sense?

Thanks!

tomsch · #6 11-25-2005, 03:07 PM

one more question: is it possible that any other component or composite or audio cable could cause this problem - or is this strictly a power cable issue?

also: the plasma hangs on a wall that has a furnace on the other side - overall our house is old and most likely has a loaded electrical system.
AND! (don't crucify me!) a heating vent is close by.

I turned off the heat to that vent yesterday to see if it made any difference and nothing was real obvious what causes the noise - after a while it just looked as if the problem was there most of the time, but sometimes it was gone in no obvious correlation to what I was doing.

Frustrating!

mtrycrafts · #7 11-25-2005, 03:48 PM

Quote:

Originally Posted by tomsch

one more question: is it possible that any other component or composite or audio cable could cause this problem - or is this strictly a power cable issue?

also: the plasma hangs on a wall that has a furnace on the other side - overall our house is old and most likely has a loaded electrical system.
AND! (don't crucify me!) a heating vent is close by.

I turned off the heat to that vent yesterday to see if it made any difference and nothing was real obvious what causes the noise - after a while it just looked as if the problem was there most of the time, but sometimes it was gone in no obvious correlation to what I was doing. Frustrating!

Yes this is frustrating for sure.
It is free to experiment with different outlets

If your plugs are 2 prongs, not polarized, swap that around too.
Also, a cable TV ground isolator is rather inexpensive, $10 or so, and solves many problems:
http://www.cencom94.com/gpage.html8.html

tomsch · #8 11-25-2005, 05:02 PM

I went back and did some more experimenting after some advice from Eric - I unplugged the cable feed and all of a sudden the problem was gone!

went ahead and ordered the little part - keeping my fingers crossed!!!

Thank you guys for your help!

mtrycrafts · #9 11-25-2005, 08:51 PM

Quote:

Originally Posted by tomsch

I went back and did some more experimenting after some advice from Eric - I unplugged the cable feed and all of a sudden the problem was gone!

went ahead and ordered the little part - keeping my fingers crossed!!!

Thank you guys for your help!

I am pleased that we are able to help with this headache. That is why we are here.