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My problem is a little unusual. I run a digital media company and have deployed an instore advertising system to Australia national electrical goods retailer. A simple view of the system is a PC outputting component video to a high definition bandwidth 8 way distribution amplifier. This then connects to more amplifiers through expansion ports to around 60 TV screens with component inputs. They are a mixture of LCD and Plasma screens from Sony, Samsung, Panasonic, Hitachi, JVC etc.

The PC is a local supplied unit with Intel Core 2 chip, ATI1650XT video card with 256Mb RAM using a component break out cable from the S-Video output. The PSU of the PC is 275 Watts and the card I found out should have 400 watts minimum. The card outputs at 720p at 60Hz. We show a loop of WMV and Flash files, some encoded to HD, but most aren't.

The problem is that in around 40 of the 100 stores I have deployed this to, some but not all screens in the TV wall suffer highly visible flickering on the screens. The system was installed by different installers around the country and not all stores suffer the problem although they all have the same PC. Recent testing in some stores had also found the following:

* If I connect a digital STB to the system instead of the PC and run it at 720p 60Hz, or 1080i there is no problem
* If I connect the PC directly to an affected screen, there is no problem
* If I swap cables on the screens, the problem follows the screen
* If I increase the PC output to 1080i the flicker improves but does not go away entirely. (Note, this card can only do 1080i at 30Hz)

Everything points to the PC, but when connected to one screen there is no problem. One last thing I noticed is that when I had my helpdesk VNC in to increase to 1080i while I watched in store, one screen I was looking at was flickering with the PC desktop on, but as soon as they opened up the ATI Catalyst Control Centre on the desktop, the flickering stopped.

When they closed it down it came back. This is just bizarre and I would welcome anybody's ideas or things to test further as my customers are at their wits end.

Thanks.

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Last Post by dewabo
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Sounds like you need to up your psu to 400ws or better. you are 125watts short for the graphics card needs. A 500w psu should help the problem.

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Let me add a rule of tumb here, in the power chain, whatever compontent requires the most power will take it and everything else in the chain will settle for what's left. A 275w psu is doing double duty trying to power a 400w requirement. It is also a fire hazard. A 550w or even a 600w psu would be better suited for the job.
Just another through, some of that fliking could be caused by the lighting system in the stores.

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Thanks dewabo. We are aware of the PSU issue however I just tested another PC the other day with an nVidia card in with ample power and still this flickering occurred. We also turned off the fluro lights and saw the same problem. Still no luck.

One that line of thought though, shouldn't the PC have the same problem when connected directly to a screen. In this case it doesn't, it's only when run through our distribution system it happens, but only on the PC input.

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might I ask what type of cabling are you using? Are your installers makeing up the cables as they set up the system? I don't think the computer is the problem. which one seems to have the wrost flicker, the ones closes to the source or then farest ones away from the source. If it is the closest ones than it could be over ampiflied and the farest seems like a lost of signal. If it is the far ones try a RG6 duel sheilded cable.
Sorry it has taken me so long to get back to you on this.

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might I ask what type of cabling are you using? Are your installers makeing up the cables as they set up the system? I don't think the computer is the problem. which one seems to have the wrost flicker, the ones closes to the source or then farest ones away from the source. If it is the closest ones than it could be over ampiflied and the farest seems like a lost of signal. If it is the far ones try a RG6 duel sheilded cable.
Sorry it has taken me so long to get back to you on this.

HI the installers had the cables prebuilt but I'm suspecting they weren't the best quality cables. Some runs are up to 20metres long despite connecting to the first distribution amplifier only 4metres away. The excess cable is just coiled up by the equipment cabinet. (Have some shocking photos of the installation I can send if interested).

The only question with that is that each site has been live for up to 6 months now, yet these problems haven't always been there since day one which you would think if installation was the problem.

Cheers,

Dave

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Forgot to add - sometimes these idiots mixed RG6 with RG11, have used audio connectors to join video cables, run power alongside video cables etc so it's really hard to tell. Having said that, I've had a different, trusted AV team go in and rectify some sites and they can improve the quality by recabling correctly but some screens still show the flickering.

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At these sites that still have the flickering, is there any type of high voltage equipment close by. This is sounding more like some type of interference or it could be the monitors themselves. By any chance can you fine turn the moniters. Is there an amp close to the ones that are flickering, if so can you make adjustments at the amp? I've seen this problem before and it almost always turn out to be interference of some sort. It can drive you to drink!

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I've reread your post where you said you had 20 meters of cable where the unit was only 4 meters from the dist. amp. Let's see, a meter is just a bit longer than a foot(12 inches) so 4 meters would be like 5 feet. 20 meters would be close to 25 feet, there would be signal lost in that cable unless you turned up the amp to compensate for the lost and most video amps don't boost the signal by much. I think most video amps will boost like 10db,which is maybe a milivolt, so acturally the closer the monitor is to the amp the better the picture.

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