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BarcoData 808 Green tube focus problem

Discussion in 'Projectors' started by tomgilmartin, May 3, 2006.

  1. tomgilmartin

    tomgilmartin Guest

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    I am running a BarcoData 808 (not s version) with a laptop VGA output at 1024x768 60hz refresh. I have a couple questions for the more experienced guys on the forum regarding focus/convergence:

    1. Why does one need green only convergence? What do you converge to?

    2. My green tube has a ghost image above and to the right of any green object on the screen. I created a black screen with yellow letter "A"s all over it. With binoculars I can converge the red onto the green, but there's always a sort of green "halo" above and to the right of the converged A. I didn't try adjusting the neck magnets yet. I removed and re-installed the lens. I also didn't adjust the G2 yet. Red is focused razor sharp, blue not too bad (has burns on CRT) but the green is really bad. Movie images really look quite good except for the green halo visible in certain high-contrast types of shots (white on black for example). Also the EM focus doesn't have any effect at all. Looking through binoculars and cranking EM focus from 0 to 99 I can't see any difference in the green focus at any point on the image.

    3. The bottom of the screen is focused much sharper than the top for all tubes. Is this a schliempfung problem? I tried playing with the washers on the lenses but it didn't change anything.

    Thanks is advance, this forum is great.
  2. cosaw

    cosaw Member

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    Its useful when aligning one or more projector images either on top, or partly on top of, or next to each other. Look at the blending edge blending thread and you'll see what I mean. For one projector on its own convergence on green is not really needed as far as I know so just do red and blue on green and you should be fine.

    Regarding the haloing on green - seeing as you're not getting it on red or blue then it sounds like an astigmatism problem rather than an input problem. You're astigmatism may need adjusting to get rid of the halo. I did mine recently as I was getting a shadow which was visible on text causing it to smear so that it looks like the text is beeing written twice - one time on top of the other but in slightly different positions. Make sure you've tried everything else first mind before twidling with you're astigmatism and be careful as well around those Killer voltages. I used rubber gloves and only ever one hand in the machine, rubber sole shoes and all that!

    Sounds like it - if you've got electronic focus correct that is! Don't bother messing with washers till you've checked the rest of you're install - particularly whether the pj is level and the screen is square and you've got toe in of lenses roughly right. Once that's all spot on THEN start with the washers.

    A couple of recent threads on this:
    http://www.avforums.com/forums/showthread.php?t=319028

    And check further down on this one:
    http://www.avforums.com/forums/showthread.php?t=332014

    Hope this helps :)
  3. tomgilmartin

    tomgilmartin Guest

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    After finally getting the cover off I played with the astig magnets on the green tube - WHAT A DIFFERENCE! Now I just need a new blue tube (it has some burns on it - little icons on all images). Anybody selling one? I don't mind used, just want one without burns.
  4. Alaric

    Alaric Member

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    Hi there,

    I've been looking for a green tube for my BG808 (non S) which has the same tubes as the data. There is a red, blue and green on ebay, but the green is worthless, i'm not sure the blue is much better though.

    I've not tried playing with the astig magnets on mine, how did you do it etc ???

    Prior to you doing that i was going to surggest it may be the dynamic astigmatism in the service menu as that can give ghosting.

    Corner/edge focus is done by Shemflug (lens flapping) the Graphics have infinetatly adjustable which is a screw thread (Gee, wow) the data's are done by washers....Some guys here have had sucess in calculating the washer overall thickness from the barco Lens program and manufacturing the thickness out of various materials to pack the lenses.

    Cya,
    Lee
  5. cosaw

    cosaw Member

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    Lee,

    Have you read all the guides to astig adjustment on the internet? Curt's, Moe's Realm, eboytoyz, barco manual stuff etc. I can post links to guides if you need so won't go into a step by step procedure here. Instead I'll post a few things I learnt. Just ask if you need more guide links.

    I think on this page there is a link to a guide for the 808:
    http://www.curtpalme.com/CRTReplacement.htm

    A couple of things maybe worthy of note.

    Firstly watch you don't kill yourself! I wore tightly fitting rubber gloves with only ever my right hand in the projector (the left glove was a just in case my brain wasn't in gear) and thick rubber sole shoes. THESE ARE THE PRECAUTIONS I TOOK - I AM NOT QUALIFIED TO ADVISE ON ELECTRICAL SAFETY AND SO ANY ATEMPTS AT THESE ADJUSTMENTS ARE AT YOUR OWN RISK!

    I found the adjustment procedure noted in the Barco manuals by far the most easy to follow and successful. You'll find overall flaring and centering of the beam "core" much easier with the cross hatch than using the dots alone. To observe this you'll need to get handy with ramping up and down the electronic focus while observing the magnitude and direction of the flare/core relationship. The core should be centred equally within the flare - a cross within a cross. Roundness is done with the dots - although many say the Barco dots are not round I still found them good enough and by far the easiest to see and adjust, I tried other dot patterns but still found the Barco cross and dot the best overal pattern especially as dots and hatch can be observed at the same time. Before you start anything make sure you centre all your software astigmatism settings.

    Regarding the astig rings - on Barcos each little knob on the astig rings opperates a single pair of astig magnet rings. Rotating the little knob moves the rings of a pair in opposite directions. So depending on you're machine you'll have 1, 2 or 3 little twidly knobs per tube neck. Knob 1 (closest to the neck card) operates the pair of "Two Pole" magnet rings, knob 2 operates the pair of "4 Pole" magnet rings, knob 3 operates the pair of "6 Pole" magnet rings. 2 Knobs is most common giving adjustment for two and four pole magnets. Note - rotating a pair of magnets in the same direction by keeping the knob still but dragging the whole ring and knob either clockwise or anticlockwise will sometimes cause a raster shift - you' can use this to you're advanatage sometimes in final mechanical positioning of the raster.

    The adjustments take a bit to get your head round and can be confusing until you've actually experimented yourself - I spent several hours at a first attempt and didn't get the things quite right. I re-read and re-thougt and had another go in a couple of weeks and got things as best I could. The improvements were quite visible as the settings on my machine were no where near optimal to begin with.

    Start on green and practice (its by far the easiest to see this colour), blue you will find the most difficult as with every adjustment it seems! Once you get it right - undo all your hard work and then recorrect it - its a good way to practice and it allows you're brain to work through the routine. Make sure you're completely happy that you know what you're doing on green before attempting red and blue - reds not too bad but I found blue a bit of a nightmare.

    So how do you know what you're looking for in the finished picture? I found, through experiment, an extremely good test in looking for ghosting which the eye can see with a fair amount of accuracy - not sure if you're using a PC but I'll post this anyway for the benefit of all. Use your computer desktop and set background colour to a medium grey and icon text colour to white. Drop around 8 - 10 .txt files around the perimiter of your screen with a few in the centre. Rename each text file with names HOHOHOHO1, HOHOHOHO2, HOHOHOHO3 etc. Make sure you use CAPS LOCK, you can use a plus sign instead of H if you like but I found H works better.

    You're gonna use the text of each file name to check for ghosting. Starting on green (cover your blue and red lenses with lens caps). With the text and the contrast control you can see which way the ghosting is skewed and also how crisp the picture should look once astigmatism is done. As you'll be turning the contrast control down you'll need the room nice and dark to observe the effects.

    Leave brightness at normal viewing level, and start with contrast normal. Stand at the screen and turn contrast up until definite flaring on objects is perceived. If your astig is bad on that tube you'll see a distinct divergence of the HOHOHOHO text into text that looks like HOHOHOHO is written twice (that is once and then once again ontop of itself but in a slightly different place). As you turn the contrast higher and higher the text will diverge more and more allowing you to see the magnitude and direction of the error. If the text does not diverge when it flares but just gets fatter in all directions equally then your astigmatism is fine! I beleive flaring occurs much sooner than people actually beleive - to view what tight astigmatism looks like turn you're contrast lower and lower and watch the divergence dissapear and the text become tight, with you're contrast down at around 25-30 you may find that you can no longer perceive flaring and your picture looks really crisp - keep this in mind as the sort of picture quality you're aiming for with normal contrast levels - this will ensure your astigmatis is adjusted optimally.

    Hope this helps - my astigmatism is great now and the picture looks better than ever. Remember though this won't get rid of ghosting from cables or ports so don't confuse the two.

    Edit: Thanks Mr H for putting my warnings in Red, should have thought to myself! He really does read every post you know!!

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