Problems with my HTPC (interference?)

[push]

Everything is fine, except for occasionally I get 'noise' on my monitor. I am doing VGA out through my 8800gts to a 32" sony bravia. 60-70% of the time it's fine and dandy. But every once in a while I will get noise on the screen that looks like a tv channel that isn't coming in just right. The background color will change a little and it will get some horizontal lines. My first thought was unshielded VGA cable which is being affected by my wireless mouse/keyboard, or wireless network, etc. Well, looked at the cable and it has an RF choke on it, so I thought I may be able to rule that out, unless there is a short in the cable somewhere? I hooked it up to my laptop and didn't see the same problem, but I didn't run it nearly as long and at the same resolution (1360x768). I read something about a ground loop, but I have the TV and PC plugged into different outlets and only the pc is grounded. Any other ideas?

 

[Informant X]

Hmm, not sure it's interference from the wireless sources around it. My HTPC sits next to my TV and I have no problems using a HDMI cable. Also my HTPC has a wireless nik in the back, plus a wireless usb keyboard/mouse dongle out the back too. Also next to my tv there is my Wii which is wirelessly connected as well.

 

[Modelworks]

If it were a ground loop it would happen all the time.
It could be a failing cable or connector, how long is the vga cable ?

 

[kalrith]

I'm not sure if this will help, but I've been getting something similar on my HTPC (also running at 1360x768) ever since I replace my 9500GT with a 4550. It will frequently flash some horizontal lines all the way across the screen about 20% from the top.

I didn't change any settings when I installed the new video card, so I might have to change some decoder settings or something like that. I was using a DVI-to-HDMI cable with the 9500GT, and now I'm using an HDMI cable with the 4550. I might just have a bad cable.

Do you have another VGA cable you can try? I'm going to try swapping my HDMI cable to see if that helps.

 

[push]

Hmm, not sure it's interference from the wireless sources around it. My HTPC sits next to my TV and I have no problems using a HDMI cable. Also my HTPC has a wireless nik in the back, plus a wireless usb keyboard/mouse dongle out the back too. Also next to my tv there is my Wii which is wirelessly connected as well.

I sat there for a good 20 mins moving wires around to see if I could get two wires close to eachother and reproduce the problem consistently. No luck so far.

If it were a ground loop it would happen all the time.
It could be a failing cable or connector, how long is the vga cable ?

My cable is about 4-5' in length, I may go pick up another cable and swap it and see if the problem disappears.

I'm not sure if this will help, but I've been getting something similar on my HTPC (also running at 1360x768) ever since I replace my 9500GT with a 4550. It will frequently flash some horizontal lines all the way across the screen about 20% from the top.

I didn't change any settings when I installed the new video card, so I might have to change some decoder settings or something like that. I was using a DVI-to-HDMI cable with the 9500GT, and now I'm using an HDMI cable with the 4550. I might just have a bad cable.

Do you have another VGA cable you can try? I'm going to try swapping my HDMI cable to see if that helps.

My next choice is to get a dvi -> hdmi converter and see if that doesn't work if the vga cable fails.

 

[JoeBleed]

with it plugged in and giving you the problem, try wiggling both the monitor cable at both ends and the power cable for the monitor on the monitor end making sure it isn't lose. As well as wiggling both ends of the vga cable, try and bend it back and forth going the whole length of the cable to see if the color shift changes.

Your failure sounds like a common problem when vga cables go bad for what ever reason and cause color shifts and picture objects.

 

[push]

Just as an update, it looks like it was the vga cable. Bought a new cable and tried it out, nothing on screen so far. I compared the cables, and the new cable was much thicker which makes me wonder if the old cable was even shielded or if it just relied on the RF chokes. Anywho, thanks for the help!

 

[JoeBleed]

When you have used the new cable long enough and are sure it is the old vga cable that was the problem, you can always cut the old one to see if it was shielded. IT probably was though just using a little thin foil. I use several of the thin ones, even with out the rf chokes at work for extension cables and they are fine.

However, when i had to run a few through the celling at 50 feet or so for projector mounting i did spend a little more for the thicker ones to hopefully avoid interference from the florescent lights.