I'm almost done with a big job, and found a new problem, One H-10 is distributed to 3 different TV's around the house over Component Vid, used a CE-Labs Component splitter, 2 TV's work just fine, (32" sony wega, 52" Mits DLP)

The 3rd, 37" LG LCD, has horizontal purlple lines that slide upwards on the picture.

had the same problem in the showroom with a new projector install a while ago, ended up using 3 Kramer Composite video isolators,

you guy's have any other (prettier) solutions??

Yeah, that sounds like a variety of ground loop problem, especially if it is moving upward real slowly. Or it could be a poor ground on one of the video leads; I saw something similar with NTSC video several years ago, but the picture was even worse because there was only one shield and it was poorly connected.

Check to see if the noisy display is on the other phase of the power line. This has been discussed many times in different threads and is too long to go into at this time of night.

Also, temporarily disconnect the display ground (it DOES have a three-wire plug, right?) and see if the problem goes away. That would still indicate ground loop or power phase problem, I can't tell if it would pin it down.

DON'T leave the ground disconnected as it is neither legal nor safe.

You could test the ground loop theory by running an extension cord from the offending set to the outlet where the good sets are plugged in. If that fixes it. Have sparky swpa the breaker to the other phase

Yes it's moving rather slowly, and I think that there are green bars in-between the purple bars.

I'll try both your ideas, they sound great.

any one else???

I had the same purple & faint green bars/lines slowly rotating through last year, moto hd box, avr3805, se50hd proj, component vid cables. Solution - run cable feed through surge strip before cable box. Problem gone. Simpler system, but sounds like same type of ground loop situation. Other techs had also suggested ground issues on line voltage which may certainly turn out to be the problem in your sitch. I come from the land of mobile 12 volts where we either had to get everything to the same potential to stop errant eddy currents or isolate to stop them. I always liked getting everthing at the same potential, seemed like a more simple, direct route to solving problem. Sometimes isolation was the only solution especially when dealing with different manufacturers stuff in the same system. We don't ever seem to have that set of circumstances here now do we? Erik

Brent, Another question would be does the 3rd TV have a cable box, or cable hooked up to this set...???? cable is notorious for ground loops...actually most of the time hum is from cable...even more so than electrical...Because most hum bars are D.C. created...If cable is hooked up to any of these check that out..DC groundbreaks are cheap...


THXRick

No cable

I have an in-house cable system (five modulated channels) , but the antenna is going through a Panamax surge strip before going into 2 Channel Plus 3x8 distribution amps.

The LCD has a cable coming from the head end, and the component video, The modulated channels don't have any problems, just the Component video.

Would it help to tie a ground wire from the distribution amp to the surge protector, (the wall wart does go through the surge strip.)

Does the problem go away if you disconnect the cable from the lcd?

Brent,


Your problem is definitely a ground loop.

Moving the offending electrical circuit to a different breaker (changing the phase) should correct it. But that doesn't ALWAYS work.

I suppose you could use three composite video loop isolators to break the loop....

Power phase could be the problem. The extension cord idea is a GREAT one, and be sure to use a grounded cord.

Grounding could be the problem. You have to think creatively and deeply about the grounds.

For instance, you only have an antenna. Sometimes the antenna output has an electrical connection to the mast and the mast is clamped to an old cast iron vent pipe. That could be a ground, or could be one when it rains. Or even gets foggy (just for real complications!

Your cable runs might have been pulled around an electrical box and the insulation scraped off, making a very unpredictable power ground connection.

rguy's idea of grounding everything is basically the way video and RF products are grounded. They don't hum; we had hum in audio/video back when amplifiers were star-grounded with no attention paid to the possibility that an actually grounded input, such as audio and video from a cable box, would be connected. Somehow they fixed that, and I think it was by combining judicious use of star grounding for audio-only circuitry and grounds all over the place, that is, ground planes, for other grounding.

I had a system with horrible hum bars in it, but that was at the end of the first day of interconnection of three rooms at quite some distance from one another. I told my client I would troubleshoot the hum the next day. By the time I had everything connected, there was no hum anywhere. Enough overlapping grounds often reduces ground problems.

Just went through the same problem. Had an electrician put the TV and stereo on the same circuit, something the original installation company failed to do, that reduced most of it. The rest of the interference was coming from the Russound A-Bus system that was on the same circuit as the stereo. Three car stereo floating ground eliminators connected between the A-Bus inputs and the receiver fixed the problem.

Usually a ground problem for sure. I have always used a furman AC 215 conditionor/ supressor. WOrks like a charm. I once called fujitsu about this, and their tech told me to cut the ground off the plug to fix the problem.....??? what a nut. Good luck

Probably not related to your problem, but I had a strange one in the store yesterday. We put up one of the new Black gloss Sharp 32's (Sweet looking, by the way!) and hooked it up to the HD Sat box that runs both it and the plasma next to it. (hint here) The plasma is gone at the moment, so just the Sharp was hooked up to the CV Distribution Amp. There were horrible wierd bars moving around in the picture. Played around looking for loose connections and power wires - nothing. Unplugged the component video wire that used to go to the plasma, and were just lying there not connected... Problem solved. The unterminated CV wire was creating reflections back into the amp, and ruining the picture. Just something to keep in mind...

Hi everyone,

I have almost the identical problem with the slow, upwardly scrolling purple and green bars. I'm using a Sony plasma connected over component to a Sony amp that has two component inputs for DVD and HDTV.

As suggested above I tried disconnecting the cable feed and that solved the issue. However I obviously would like to have cable TV in the bedroom and was hoping that someone could tell me how to fix this.

I tried, again as suggested above, to pass the cable feed through a surge protector; but to no avail. Now it was a "cheap" surge protector ($40ish), and after reading around a little more was wondering if using a Monster Powerbar, retailing around $200. I have read from numerous people that the Powerbar solved this problem for them. Will this do the trick for me, or am I wasting my time? And can I save some bucks and find a better/cheaper solution?

I see THXrick suggests a DC Groundbreak. I don't know what that is, or whether it would help in my situation. If it is what I need, who makes them and where could I get one from? And finally, will a DC Groundbreak work with my HDTV Cable Box and a modulated CCTV channel that I soon plan to add.

Thanks for any help in advance, it is greatly appreciated.


Ed.

This message was edited by edfraney on 10/12/05 22:35 ET.

That amp does not have any isolation between its outputs, then. It might be a distribution amp in that it can feed the proper voltage to more than one 75 ohm load (per cable), but the thing that distinguishes good video DAs from audio DAs and from cheap video DAs is some kind of isolation from output to output.