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New Power Supply

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  • #16
    Hi Paul

    I removed the grill but forgot to mount the fan on the outside, however with the speaker grill removed its a lot better, even without the projector switched on you can feel the cool air flowing past the lamp. I will leave it the way it is for the moment, I dread lifting it on and off from where it usually sits. I pulled my sciatic nerve a few weeks ago on my side and lifting that thing around ain't nice. I have done that nerve before and it usually comes right after a while, usually after doing certain exercise. must be age catching up with me


    I found my old bits and pieces, the reflector I cut the end off was from a Philips ELC 13163/5H lamp. Thomas is the EHJ lamp you are using the same filament as the one below. I was hoping to find a lamp with a vertical type lamp filament, as I think the spread of light outwards to the reflector would be more even.
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    Where the projector sits there is not a lot of room at the rear.
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    Present lamp.
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    This is the one I made up but at present don't use it, the lamp can slide forward or back inside the mirror. There is plenty of adjustment and have tried in the GS1200 but light wise by moving the lamp while it was running just didn't quite make the grade.
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    • #17
      Well Graham, the GS1200's weight is a function of the age of its owner. My GS1200 now weighs about 50lbs!
      I have to say that mounting the fan inside the case is a much neater arrangement than on the outside. Even though the air flow rate will be improved by mounting it on the outside and pushing air in, the fact that you can feel cool air flow at the lamp with the projector off means that you have improved the cooling situation. One thing I am looking at is the use of a 'plenum' which is basically a short piece of air duct which will lift the fan away from the inside surface of the metal grill of the back cover by about 3/4 ins. Done right this will prevent the fan from running in a stall situation, while still mounting the fan inside the projector as you have done. This can also be acheived by using spacers to lift the fan away from the metal grill, thus introducing some 'by-passing' of the air and moving the fan operating point to a higher air flow condition.
      Last edited by Paul Adsett; January 16, 2024, 07:13 AM.


      • #18
        Hi Paul

        That's a good idea about moving the fan away from the grill. I used thick stick on rubber feet between the fan and grill. The fan is not pressed hard against the grill, there is a gap, not sure how much but there is some, moving it away further would be even better as you suggested. Food for thought the next time I lift the projector off.


        • #19
          Ran a 1200 foot Scope reel last night, great way to see how much light I am getting on the screen, as there is always a drop of with Scope. The image did look brighter than in the past, going from the max 21.5 volts on the old power supply to 23.5 volts on the new one did make a noticeable difference. Glad I put in extra cooling in at the same time, it does need it. I took a screen shot last night which I think the title of the film below sums up of owning a GS1200. Considering they are around 45 years old now I don't think the Elmo designers back in the 1970s ever expected the GS to be around this long.

          PS I still cant figure out where all that weight comes from.
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          • #20
            I have now added a 4 ins 24vdc fan to the outside of my GS1200. It connects to the external lamp power supply and only powers up when the external supply is switched from preheat to full 24vdc. It is pushing cool outside air into the interior electronics and also into the inlet of the main projector centrifugal cooling fan. I have removed both speakers and both cloth mesh coverings and I can now feel air coming out of the rear speaker grills and also coming out of the lamp house cover, so it will certainly help keep things cooler. I have installed a quick electrical disconnect to permit quick removal of the back cover. No doubt that the air flow would be much greater if the metal grills were machined away to permit a free flow of the fan, but I am not about to do that as it means a non reversible modification to the projector.

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            • #21
              Fantastic Paul at present we are into the 30C summers which is pretty warm for those old projectors, extra cooling that you have done can only help the electronics and lamp cooling which by now are getting on a bit.


              • #22
                Hi Graham! That looks good with your cutted Mirror, but you must turn the Lamp 90 Degrees. The Coil in the Lamp must be stand horizontal not vertical.
                Look at my Photo.


                • #23
                  Anyone has done a lamp conversion with projector LCD bulb? The LCD bulb is indeed expensive, around $250 but with now there are plenty dead LCD projectors lying with active bulbs, it becomes cheaper here in Asia for the second hand ones. What will you think the quality compared to Graham's method here?


                  • #24
                    Thanks Thomas

                    I will do just that, this time in the horizontal position


                    • #25
                      For some reason I seem to be getting exceptional bulb life with my DIY external 24vdc power supply. The present 250w ELC bulb is now up to 60 hours, and that's with it overrun to 24,5 volts! Not sure if this has anything to do with it being DC voltage (no possible filament vibration) or the very gentle warm up of the lamp provided by the power supply circuit, or a combination of both. Or have I just been lucky with this particular lamp? I don't know the answers right now, but I do know that my unmodified GS, using the 200w ESC lamps usually results in ESC lamp failure in less than about 25 hours. Or is the ELC just a much better bulb than the ESC?
                      Whatever, I am just happy that right now I seem to be getting both exceptional lamp life as well as significant increased brightness.