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DIY Projector Lamp

Discussion in 'Home Cinema Building DIY' started by dooz, May 11, 2005.

  1. dooz

    dooz
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    Hi Folks,

    You're probably going to think I am mad for even suggesting this but I am toying with the idea of building an external light source for my projector to reduce the cost of lamps.

    I have a Philips cBright XG2 which has just finished it's first lamp (cuts out after about 10 minutes). I went to buy a new one and nearly passed out when I saw that it would set me back £450 at least :eek:. I pulled the old lamp out and was surprised to see that not only did it look fine but it consisted of nothing but the housing and lamp - I had expected some fancy control circuitry for some reason.

    Well that got me thinking.

    Thought #1: Would it be possible to but a cheaper lamp for another projector make and put it in the current lamp housing? Trouble is I don't know the exact spec of the current lamp (it's 200W) or where to look for it.

    Thought #2: At the end of the day you just need to shine (a lot of) light through the projector. The bulbs are expensive because they are small and very bright to make the projector mobile. I don't need that mobility so a huge cheap bulb wouldn't be a problem on that front. Assuming that I can make a light box and position mirrors such that the light is shone through as per the normal bulb my only problem would be tricking the projector into coming on without a bulb in place and that is where I am hoping to get some help.

    I don't think the light box will be that hard to make. I realize that the real bulb produces very white light etc etc. I was thinking of using either low voltage halogen or perhaps short fluorescent tubes as both produce fairly white light and I think a tweak of the color settings on the projector should take care of the rest.

    Anyway I think I have rambled on for enough for now. I am really interested in getting this working so any ideas will be greatly appreciated. My electronics skills aren't fantastic but I am willing to learn what I need to make this work.

    Thanks.
     
  2. Daftboy

    Daftboy
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    Spec for the bulb should be in your operation manual under the general product specification.
    A word of warning, BE CAREFUL as the voltage and amps are lethal. Like a magnatron on a microwave.
    You may find that you could also do some damage to the ballast unit.

    Anyway, without wanting to scare you.......BEST OF LUCK
     
  3. dooz

    dooz
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    Ok, so not quite everyone thinks that I am mad which is a good thing. I suppose the first thing to do then is figure out the voltage of the real bulb. That way I might be able to find a cheaper replacement. I have checked out the manual. It just tells me the part number and wattage. I am hoping someone will be able to give me pointers about where I might look formore detailed information.

    If it helps here are a couple of shots of the bulb unit:
    Complete Bulb
    Writting on Top

    I have tried switching the PJ on without a bulb, BTW, and no joy. It just tries to start the no existant bulb three times and then gives up. :(

    Thanks.
     
  4. nigelbb

    nigelbb
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    You could go the whole hog & build a projector using an LCD panel & large powerful but cheap bulb. www.lumenlab.com
     
  5. gaz

    gaz
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    I have built my own crt projector and are in the procces of building a complete lcd pj at the moment i'm making it in a old PC case so it not too big esspecially if you compare it to a CRT projector check out the link in my sig,
    you can succesfully retrofit a different light source into your pj as many people allready have check out Diy audio as well http://www.diyaudio.com/forums/forumdisplay.php?forumid=12

    this is what my Pj looks like so far:
    Some simple wiring and voila
    [​IMG]
    The back
    [​IMG]
    The front
    [​IMG]
     
  6. dooz

    dooz
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    Thanks for the replies so far.

    I have considered building my own projector but to be quite honest it feels like a waste to do it when I have a perfectly good projector just missing a bulb. I suppose the problem is that the cost of a new bulb is about half the cost of a new projector that potentially has a bulb that lasts much longer and is cheaper. Sigh. Anyway enough moaning.

    Any ideas how to proceed? I am wondering if the PJ has a test mode or something that allows you to start the electronics without starting the lamp. Maybe <clutches for straws/>

    Cheers
     
  7. shodan

    shodan
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    Gaz, I'd be very interested in doing the LCD one as a kind of project. Any chance you could PM the details of where to source the parts from? I'll be combing through the diyaudio website looking for directions on building one as I don't want to pay $20 to get the instructions!!!

    I've just read another thread on their where a chap talks about using white LED's in a cluster. that sounds like a "brilliant" (pun intended) idea to me! I've got a 21 LED torch which is far too bright to look at, runs off 3 AAA batteries and produces no heat so would not need a fan!
     
  8. dooz

    dooz
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    I've considered using white LEDs but when I looked in to it they didn't seem to be worth it. They are still quite expensive, especially when compared to low voltage halogen. They alos loose brighness fairly quickly especially if they get warm so you would probably still need a cooler. I imagine you would need a huge number of LEDs as well to give you enough light to make a worth while PJ. Still YMMV.
     
  9. shodan

    shodan
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    Gaz, I checked out the link in your sig and have registered there.
     
  10. gaz

    gaz
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    To my knowlege i don't think many (if any people) have succeded in making a projector on indeed retro fit LED's into a projector the principle of the diy projector and also commercial projectors are the same when you break them down its simply:
    Bright light-lens-lcd and then finally a triplet projection lens all shop bought ones will be of a folded design by using mirrors and a diy design also sometimes also use mirrors, naff resolution of small (ie smaller than 5") LCD screens is the reason why these pj's are bigger than shop bought ones

    Going back to the question though you can change the bulb to different one though it will have to be done with caution if your ballast were light a different model bulb of the same wattage if may even work the projector but the new bulb may run a greater temp, and or the ballast may need to draw more power to light it meaning more heat inside your pj case resulting in a fried LCD screen which could result in dead pixels you could however as you suggested before use an external box of some kind and add a couple of pc fans blowing across the bulb this would cool things down but increase projector noise and you could also attach a heat sink and fan on to the light box similar to the heatsink on your proccesor on your PC
    At the end of the day it will be possible although if your still under warranty then you would have to kiss it goodbye

    By the way the bulb i am using in my Pj is a 250 watt metal halide bulb which cost me from a local shop £25 its 19000 lumens and can outlast pratically and projector bulb on the market...................... so if you mange to sort it out its "CHEAP PROJECTING AL THE WAY HE HE HE ......"

    Regards Garry

    Shodan I look forward to seeing you on there unlike lumenlab we don't charge for for any info or design's and we have listings of places to get parts from, mods on there are Myself, Matt site owner and Mark

    Anyone else interested come along :D its free........
     
  11. gaz

    gaz
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  12. AVmaster

    AVmaster
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    Dooz. The thing I can't quite get my head round is why your projector actually works for 10 minutes before switching off if it's the bulb which is causing the problem.Does this mean that it actually lights up and produces a picture for 10 minutes?
    If this is the case then I would reset the lamp meter as it seem that it's the projector knows how long the bulb has been used for and may be shutting the PJ down as it has reached its expiry limit. Therefore in theory, by setting the meter back to zero should fool the PJ into thinking tht you have fitted a new bulb as you may have to do this eventually anyway.
     
  13. theritz

    theritz
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    dooz,

    The primary issue with using a different lamp is the "strike" voltage - the balast produces a serios "hit" - in the thousands of volts, to get the lamp to start. If you substitute a different lamp from a different projector, then it needs to be rated to start at the same voltage that your projector produces at start-up, as well as the same voltage to continue runing. I dare say that you might be able to find a similar rated lamp with some research, but if it's outside tolerance it could refuse to strike/destruct/heaven knows.....

    If resetting the lamp counter doesn't work then the lamp is fubarred. The projector won't power up without a lamp because it's start up routine expects the lamp to strike and the voltage to stabilise - some part of the logic circuits is not getting a message to say that all is well with the lamp startup, so the projector is (presumably) going into/staying in stand-by mode.


    S.
     

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