1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

CRT Video Noise - quest for perfection

Discussion in 'Projectors, Screens & Video Processors' started by helipilot, Dec 16, 2001.

  1. helipilot

    helipilot
    Active Member

    Joined:
    Sep 20, 2001
    Messages:
    314
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Hamilton
    Ratings:
    +19
    One for the Techsperts !


    I have an Imager 901E CRT projector, which is basically a rebadged NEC 9PG. I have fitted three new tubes and have had it ISF Calibrated by Gordon. The convergence, focus and astigmatism are all well set up. I do however have a slight problem with video noise. The noise is not perceptable at normal viewing distance but it is there when you stand a couple of feet from the seven foot wide screen. There is no visible line structure due to setup so perhaps the noise is more visible because everything else is so good.

    Initial thoughts were that my HCPC was introducing the noise. I have since connected an old Hitachi 20" PC monitor which has 5 BNC connectors in place of the projector. I did this by extending the cables from my ceiling down to the monitor. In other words the only thing that was changed was the display device. There is no visible noise on the PC monitor. My conclusion then is that the video noise is being generated internally by the projector.

    The projector produces a stunning smooth three dimensional image which is truly film like, as far as I can see at least as good as the local UCI. The point is I am "nit picking" here, just trying to get as close to perfection as possible.

    Does anyone have any ideas that would reduce internal noise within the projector. Initial thoughts :-

    1) Could I have a dry joint or a faulty component somewhere ?
    2) Could I have a struggling power supply ?

    Any ideas would be appreciated.



    thanks
     
  2. jrwood

    jrwood
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Could try changing the power lead to the projector or borrowing a friends PC to check its not your graphics card.

    James

    p.s Next time you go to the cinema, go to a UGC cinema imho they have far better screens than the UCI's.
     
  3. Chris Frost

    Chris Frost
    Well-known Member

    Joined:
    Jul 14, 2000
    Messages:
    2,743
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    86
    Location:
    Cheshire
    Ratings:
    +107
    Noise can come from various different sources. It's often difficult to pinpoint without seeing it first-hand, so here are some general areas to look at: (Check these, in this order)

    EHT noise - an interaction between the power supply and the frequency of the incoming video signal. Most often seen as fine horizontal bands running up or down the screen when using a PC source. Check the manual for a projector control to minimise this effect.

    Signal cable noise - a by-product of poor shielding or inadequate signal bandwidth in a cable. Shielding problems may appear as ghosting or random noise. Bandwidth problems are most visible where text from a PC develops softened outlines. If possible, try an alternative (or shorter) signal cable and check for mains cables running close and parallel to signal cables.

    Connection noise - poor electrical contact inside cables, at connections or inside the projector where ribbon or edge connectors are used. Unplug and reconnect connections.

    Inadequate signal strength. Similar to bandwidth problems. Try a shorter cable. Seek professional advice. RGB Communications Ltd imports the Extron range of computer video interfaces to solve these problems.

    Of course, you may have a dry joint or bad component, but I would expect the noise to be seen with a normal video signal as well as the PC. Then again, you may have simply reached the limits of your projector.

    Richard A, Roland, or Gordon may also be able to offer advice.

    Regards
     
  4. uncle eric

    uncle eric
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Alan,
    If you can describe what the Video noise actually looks like there is a fair chance it could be tracked down.

    Eric
     
  5. Gordon @ Convergent AV

    Gordon @ Convergent AV
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 13, 2000
    Messages:
    13,976
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Living in Surrey, covering UK!
    Ratings:
    +2,779
    When viewed Alan's system there was more noise on the external video inputs (presumably due to design of capture card, its enviroment and also how the products were connected to it). The WinDVD player and drive didn't suffer as much.

    CRT projectors are "noisy" enviroments. One of the things Runco did to the NEC chassis was try to eliminate this noise. Video noise can be compared to background noise in an audio enviroment. Noisy backgrounds make it harder to hear fine detail...same with video. Removing it should make the image more clean and believable. One of the things I'm going to try and deal with is the noise on my 1270. So, you can expect to read about how I'm going to try and track it down and remove it ...I guess it's going to be March by the time I get there though..

    Gordon
     
  6. Roland @ B4

    Roland @ B4
    Active Member

    Joined:
    Apr 11, 2001
    Messages:
    2,238
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Reading.
    Ratings:
    +32
    There will always be an amount of horzontal creeping with this type of CRT. Even the brand new ones have it.

    The Cinemax does too.

    The lack of line structure makes me think you are running too high a resoloution. Gordon knows these projectors well so I suspect it ius well focused

    Video capture cards are always noisey but that's one for the PC section. the ones with tuner options I've heard are worst.
     
  7. helipilot

    helipilot
    Active Member

    Joined:
    Sep 20, 2001
    Messages:
    314
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Hamilton
    Ratings:
    +19
    Thanks for all the advice guys.

    It sounds like I am expecting too much. As I said, the noise is not that bad and is not visible at normal viewing distance so its not detracting from my enjoyment of the system.

    I look forward to following Gordons progress with his Sony.


    thanks again :)
     
  8. helipilot

    helipilot
    Active Member

    Joined:
    Sep 20, 2001
    Messages:
    314
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Hamilton
    Ratings:
    +19
    Just fitted the most cost effective upgrade to my system ever. (outlay £56).

    Cured the video noise problem. Image quality now extremely noise free via capture card (Falcon) and direct from HCPC with software DVD player.

    The image quality from software DVD is now astounding. Sharp focus, 3 dimensional image quality from decent source DVD.

    I am finally delighted with my projector setup!

    What was this upgrade ?

    An Enermax twin Fan quiet 350W power supply for the HCPC.

    Added bonus the PC is virtually silent (in cabinet), a major drop in noise generation from previous PSU (both in sonic and video terms)

    Anyone else suffering video noise problems using an HCPC might want to consider this option!

    I read that Jeff uses a very expensive PSU in Kryton. I now know why !




    :D :D :D :D :D :D
     

Share This Page

Loading...