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Stacks and reversed red and blue tubes

Discussion in 'Projectors, Screens & Video Processors' started by Gary Lightfoot, Aug 7, 2005.

  1. Gary Lightfoot

    Gary Lightfoot
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    This is probably a daft question, but I won't know unless I ask, and my curiosity has gotten the better of me so here goes.. :)

    I was reading another thread and someone mentioned the Barcos have their tubes the other way round to other CRTs (RGB instead of BGR I think).

    I then started thinking about the colour balance across the screen and how most CRTs fix that with modulation, but what of you stacked two identical CRTs so that one was RGB and the other BGR - would that help in any way? Would it help non modulated models, or would it just make matters worse as the colours were now being mixed R/B on the outside? I guess that would be a daft way to do it as one would be ceiling mounted and the other floor mounted. Would that help in the same way a Torus screen can help though??

    The gains probably aren't worth the hassle but things like this make me think about different ways of doing a job so wondered if anyone had tried it and what the results were.

    Also - can you swap the red and blue tubes in a CRT so they go from RGB to BGR and do things still work the same (swapping red and blue component cables over as well? Obviously s-video and composite won't work) or is there something else involved?

    I'll get me coat....

    Gary.
     
  2. Godfather

    Godfather
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    Interesting question Gary, one I've pondered myself without getting very far! I don't know if you'll get much of a response though (other than from James) as there aren't many guys with stacked setups and most CRT owners don't seem bothered about colour shift. I find it very annoying without some form of modulation.
     
  3. Gary Lightfoot

    Gary Lightfoot
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    Hi Henry,

    I guess it's more of a hypothetical queston more than anything, but it's nice to know that I'm not the only one who has these thoughts. :)

    Gary.
     
  4. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I think you'll find that stacks that are side by side will have the r and b tubes swapped omnm one PJ and that one above the other stacks will have one PJ inverted to do the same job.

    Gordon
     
  5. crteaman

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    Hi Gary, Barco and electrohome have their tubes run RGB (looking at front on ceiling) whilst Sony run BGR.
    By running an inverted stack i.e one floor and one ceiling you solve the red/blue push on each side of the screen, and most importantly give yourself enough light output for the Americans to want to crash a satellite into it :rotfl:

    I set up a stacked pair of Marquee 7500 in my lounge some time back, and a short time ago done the same with a pair of 9500, a few of the local guy's came over to see it, 'Speedbird' got to see them and was wowed, bit lounge unfriendly but a picture to die for.

    james
     
  6. Mad Mr H

    Mad Mr H
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    Currently I am working (VERY SLOWLY) on a twin projection system

    I have asked on "the other" forum for people to clarify the word "Stacked"

    I originally misunderstood this word and thought it meant one above the other, this could be in a one directly above the other "stack", as used in large screen projection to gain brightness - usually now dlp's with lens shift. or even one on the floor and one on the ceiling still what I would consider a stack.

    HOWEVER - the USA guys ALSO use the word stack for a side by side setup - this confused me to start with.

    I am trying to build a side by side set up, using edge blending contrast modulation, and with swapped tubes.



    The question has also been raised about which pair of tubes should be together, R or B (I suppose you could even do green!)

    4 of us think blues together, 1 thinks red - So a 80% 20% split :D

    WOW! a factual % post! that should please some of you ;)

    As fas as I know it is a physical tube swop and then reverse the inputs (R/B)


    PLEASE if anyone has pictures post them there, I have been compiling as many as I can.

    If all goes well then I would hope to end up with a pair of G90, 1209 series 9500 etc. (one set only!)

    conv on green is a must, I have that for my Barco's (thanks Henry)

    My reason for this was that tubes are 4:3 format and all of my films are some form of widescreen, side by side split projection would use the full tube and increase definition - I did not see the point of buying a 1209 and not using all of it......

    See my thread here http://www.avforums.com/forums/showthread.php?t=219126

    there is chat about the tube swop in that thread.

    Gary - As always your post is thought provoking and a pleasure to read, wish there were more like this.....
     
  7. crteaman

    crteaman
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    Yes you can indeed swap the red and blue tubes.

    james
     
  8. Gary Lightfoot

    Gary Lightfoot
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    Gordon et al: So I'm not completely mad then? Cool. :)

    MadMRH,

    I also thought stacked meant literally one on top of the other until I saw Art Sonnebornes pair of G90s side by side over on AVS (I'll try to dig out some pics if you can't find them over there). I hope you have good results with your project and of course, pictures of the set-up are mandatory so get a move on. :)

    James,

    I've noticed that about some (though fortunaltely thewy seem in the minority) of the USA guys on the digital forum - they like huge amounts of brightness - around 50ft lamberts (400% more than recommended for you % people out there :p ) and that seems utter madness to me. You'll get loads of image noise and artefacts and is IMHO a pefect example of how not to set one up. I think the reason Art needed two G90s was so the image brightness was enough for his screen which I believe is quite big. His set-up seems to be the Cadillac of set-ups (gee, my first car analogy, this forum is getting me into bad habits, lol) :D

    Gary.
     
  9. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    MadMrH: The stacks I have seen in US have all been side by side......You want to contact someone like Richard Ansell on the forum. One of the sde by side stacks I sw was a dual Runco 9" unit in 98.....It was on Snell and Wilcox stand at CEDIA New Orleans. Richard may have been there and can tell you who did it....

    Gordon
     
  10. Mad Mr H

    Mad Mr H
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    My post is also on avs

    Art's Stacked G90 "Really rock baby - Yeah!"

    his G90's were brand new!

    12 seat HT (so is mine) but he has loads of space....

    Spoken with Art, the one thing they did NOT do was change the tubes round, this was/is to be the next stage if required. I think the reason it stayed original could be to do with warantee and that the G90's were so sharp that they was little need, Ken who set the system up did say that a tube swop was about the only remaining thing to do....

    that system uses 2 G90's set at an angle to each other, each produces the FULL picture and so gives 100% redundancy and a bright picture.

    If work stops being busy I will actually get started, loads of kit sitting here, and I mean loads just no time to play.....
     
  11. Mad Mr H

    Mad Mr H
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    Mad Mr H :D
     
  12. Roland @ B4

    Roland @ B4
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    The reason for swapping the tubes is even out the colour shift that will occur due to one side of the screen reflecting more of one colour tube than the other. The colour shift will depend on where you sit in the room and the reflectance of your screen.

    If you are going to use a modulation system to control colour shift. Do it wisely because most of these systems reduce the lightoutput significantly before they even start working.

    Swapping tubes is fairly straight forwards in mechanical terms but check that the EHT leads are long enough. quite a lot of manufactures cut them just to right length to stop having loads of slack lying about.
     
  13. Gary Lightfoot

    Gary Lightfoot
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    Hi Roland,

    Henry showed me his Barco with the modulation cct on and off, and the difference was markedly better for colour shift. The brightness from center to edge was almost 50% dimmer (101Lux, and 54lux IIRC), and the best we could do at the time was to get it close to 40% using the modulation control, but that did mean the center became quite a bit dimmer. It did answer my earlier question of how to adjust a CRT for 12ft lamberts though. :)

    Are EHT leads easy to swap (solder?) or even replace?

    Gary.
     
  14. Mad Mr H

    Mad Mr H
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    Roland,

    Quick Q.....

    Do you really need to swop the EHT leads?
    I considered this to start with then came up with the following....

    1. Physical swop of R and B tube in second PJ
    2. Reverse R and B input on RGBHV
    (FORGOT SWITCH IT OFF FIRST :eek: )

    thats it, job done, cup of tea.

    if video composite or svhs then yes extend or replace EHT leads but that wont be for me, PC based system.

    in fact thinking about it.....

    no matter where the EHT run from in any PJ they will always run to all tubes, so think it stands to reason the the correct lenght should always be there just need to swop them over as well or you end up shortening one and lengthening the other.

    EHT leads are (all I have ever worked with) either 1. just a press fit - most tv chassis, or in the PJ's a press fit that is then sealed in place, fairly easy to remove, replace, no soldering required. on the Barco's the other end is in a nasty plastic clip fit - very easy to break!
     
  15. Paul D

    Paul D
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    I thought Art Sonnebornes twin G90 set up was unique in that each PJ fires at it's own bit of screen.

    Ie his screen is 2.35-1, and each PJ projector fires either to the left or right etc.
    He then uses a "blender" to join each picture edge together, making the picture whole.
    This way, he can use the maximum amount of phosphor(spelling?) without having to stress the tubes due to weird projection angles etc.

    Maybe the blender didn't work well and he reverted to the normal twin stack method?
     
  16. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Paul; Actually I think Art went to look at the blender at Tim's and found it didn't work well enough so he did his current stack overlayed...it was so long ago though in AVS post land....

    G
     
  17. Mad Mr H

    Mad Mr H
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    look at his pictures.......they are at "wierd projection angles"

    equipment list shows no blending kit,

    he was going for brightness as I understand, pj's look too close together to be a blend image.

    there are several other USA people playing with blending I am in touch with most of them.

    My latest 9 projector 360 deg project just changed as I did not read the spec correctly....ITS TWELVE projectors in a 360 deg projection, good tricks with the graphics designers give us our edges, will try and post pictures due to finish early october.
     
  18. Gary Lightfoot

    Gary Lightfoot
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    :eek:

    Mad Mad MadMrH!!

    What will you be watching on that array?

    Gary.
     
  19. Paul D

    Paul D
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    He plans on using it with his new XBOX 360 :devil:
    :D :rotfl: :hiya:
     
  20. Boy Lex

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    I know i'm not Roland!

    But isn't the problem that if the splitter is say underneath the blue tube, the blue eht will be shorter than the red. As far as I can tell, swapping eht leads for the two around isn't an option, as the end connected to the tube becomes part of the vacuum (someone correct me if I'm wrong). Would you not need to carefully extend one ensuring that your extension does not leak?
     
  21. Boy Lex

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    Oh yeah and switching the PJ off first... that's like tightrope with a safety net - where's the thrill in that?!
     
  22. Roland @ B4

    Roland @ B4
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    Barco are clever they make all the EHT leads the same length they know some fool somewhere is going to put the tubes rounfd the other way
     
  23. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Or perhaps it just makes the parts inventory simpler......which is also clever.....

    Gordon
     
  24. Mad Mr H

    Mad Mr H
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    I resemble that remark :D :D :D

    AS for what to watch......

    Sadly a load of drunk punters with no real care for my projection efforts, with seriously loud music in the ears till some ridiculous time in the AM using their mobile phones to send text (txt msg for the trendy ones!) messages to the screens via a pc that removes all the (fun) rude words . Will also do some graphics if the operator bothers!!!

    for those that care a bit more projection is 2.8m high 360 deg and pj's are 6m+ above the floor in a custom built ali/perspex enclosure directly linked to an air con unit

    I will of course test the system with one of my fav's - baywatch bikini special.

    BOY LEX - EHT leads DO NOT FORM PART OF THE VACUUM. dont play with them though.....
     

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