GS1200 MKIII 250W conversion

[Matthieu van der Sluis]

In the old Forum we had a topic for this in 2017 I think, but there we cannot discuss this any furter.

My Elmo GS1200 MKIII had some issues with sound, but after cleaning the head with alcohol and demagnitized it with a tool.
Sometimes it seemed like a mic was continu On and distort the sound, so most importand,... stay off from the knobs on the back.
So now this projector works perfect without any humming or high notes.
Sound is actually great now.

My GS1200 works with the origenal Fuji 24V/200W ESC lamps and gives a beautiful bright picture, but for this I had to clean the lens first.
At the moment I use this projector with the F1.1:11-30 Lens from my Bauer T610 with a converter made by Van Eck Videoservices which now fills my entire screen of my cinema (screenwide 240 x135cm, but only some films will use the complete wideness of the screen of course, cause most are 4:3)

Those origenal 24V/200W Fuji ESC lamps with extra Coil will not be there forever and are expensive, therefor I need to solve this with another kind of lamp.
Back then I did some tests with differend lamps and the Osram Xenophot ELC 24V/250W was VERY bright, but gave dark corners, which can be solved by replacing the lamp backwards.
More experienced people here said 10mm.

So I started the conversion today which was pionted out to me on the old 8mm Forum, by using a ELC lamp and an extern Transformator.
I shall write about it here while it goes on.

I have 2x 250W slide projectors and start using one of those to feed the lamp for testing.
If all works fine I buy myself a nice close Transformator, probably like this:
https://www.fpv24.com/en/isdt/isdt-s...l-24v-25a-600w


I screwed out my lampholder and could slide the socket out of the holder and keep that in tact while hanging in my projector.
I'm going to use a seperate socket for the ELC that will be connected with a long cable to the socket inside my slide projector.

My GS1200 MKIII is probably differend than on the photo's I've seen back then.
I wanted to drill a hole 10mm back, but the holes are somewhat lifted.
Also there is already a hole between the 2 that where used for the lampholder, but it is placed a bit higher.

Any tips: how to fit the lamp holder correct are welcome.

[Graham Ritchie]

No need to drill any holes in the projector, just make a bracket similar to this one I made from a piece of scrap steel, you are right though, the rear attachment hole is higher, but just allow for that when drilling some holes on the steel bracket. In this case I drilled the rear hole in a way that I could hinge the lamp on its front hole for adjusting the best alignment, with the lamp and projector running with no film and watching for even brightness on the screen during the initial set up. Thomas on this forum came up with the idea of moving the lamp holder 10mm back, and after following his advice I found it worked out fine.

One other thing I have found also since doing it, has been the Osram lamps seem to be getting a more efficient cooling, from the direction of air flowing from the projector fan onto the lamp. The results so far appear that I can see, are the Osram lamps seem to be lasting longer.

[Matthieu van der Sluis]

Oh wow, thanks,
I'm going to do it your way.
What travo do you use?

[Graham Ritchie]

Hi Matthieu

Not sure what you mean as "travo" I am guessing its short for transformer. If so I used a Elmo slide projector as a external power supply. The slide projector had stopped working long ago on the mechanical side of things so it was basically scrap but the lamp still worked, so I removed all the old mechanical stuff and ran a couple of wires direct from the old lamp holder. There are heaps of old slide projectors around, so there almost no cost involved in finding one.

Using a old slide projector in this way still means you can select a high or low setting for the lamp. Basically I turned the slide projector into a portable power supply The only thing you must remember though, is to make sure the GS1200 projector lamp switch stays in the "ON" position for the lamp cooling. I am sure someone can come up with a fail safe way of not being able to have the lamp on without the cooling fan running. But for me I just switch the GS1200 lamp switch to the "ON" for the cooling fan first, before going to the slide projector and switching the lamp on itself.

I have to say that for home use that the Osram Xenophot ELC 24v 250watt works well. I like the white light it produces, and makes "good" color films really stand out color wise on the screen.

The thing is by using a external transformer for the 250watt lamp you have completely eliminated any risk to the GS1200 transformer, even though some use a 250watt lamp on it. My thought is that these projectors are now over 40 years old, and if there is any doubt to damaging the GS1200 transformer this simple and no cost external supply takes care of it.

If as you say can come up with some kind of internal transformer that would fit inside the GS1200 then that might be even better, anyway its all food for thought, but do let us know how you get on

[Thomas Knappstein]

If the external Transformer has two Coils for 21 and 24V you can conect three Wires in the Elmo and you have all the Swiches (low and high) and pre- heat Function like an original Elmo. With the big Speakon Conectors it is easy to fit on the Back of the Machine. For the Lamp i get the best Results with the Osram base Pin Lamp 250W 24V. I have cut of the Back of a 250W ELC Lamp and stick this lamp in. Now I can focusing the Lightbeam exactly on the Frame. The Transformer is a big 400W Transformer in a metal shild Housing.

[Matthieu van der Sluis]

Ahh yes Graham, with travo I ment transformer.
I was planning to start by doing it exactly like Graham, with the slideprojector I have.

I messured the lampsocket ones and my projector did not give the amount of Amp you need for 24V250W.

Thomas, you're the one who got me excited to do this project.thanks
You did a fantastic job Thomas, but I do not think I dare to cut wires in the back.
Did you attached the Transfprmator paralel to the projector solderpoints, or did you first removed the connection from the print and than to the Travo instead?
To do this, I think I than need a close-up of the points where exactly to solder the wires.

Most of the time I use the intern speakers, but for the ones who never do,... by taking the speakers out, there will be space for an extra intern Transformator.

You even evolved this project with drilling the back of lamp that way.
Do you think, by doing that on a Fuji ESC Lamp the lampholder can stay on its origenal place?
you focus the lamp in the reflector, but how do you keep that in place.
Do you use some sort of glue for that?
or do you refocus the lamp everytime you setup the projector?

[Thomas Knappstein]

Hi Matthieu!
I desoldered the three Lamplines from the Transformer (Yellow, white, black) and solder them on the new Neutric Conector on the top of the Machine.
This Conector has 8 Contacts and I´m using 6 of them. The other three ones are going back to the internal Transformer. Now Iam able to use a Bridge Conector in the Neutric Bush and the original Transformer in the Elmo is working again. When using the external Transformer, only the three Lines to the yellow, white and black Wires are conected with the external Transformer. I hope you understand me.

[Paul Adsett]

Trying to find a 24v 250w transformer to use the ELC bulb in my GS1200. Will this be suitable? What a monster!!!!

https://www.amazon.com/Sebco-Industr...6643977&sr=8-7

[Brian Fretwell]

As it is stating they they don't know when of if it will be back in stock, even if it is suitable I wouldn't buy from Amazon. 18lb does seem rather excessive.

[Phil Murat]

Hi,

In ref transformer (P/N 1113) allows a power of 250W . Your bulb needs 250w, that means your transformer always works for 100% of its capacity, so that there is no safety margin.
I suggest you to choose model 1124 which allows a power of 300W, so that you increase margin fot 20% to prevent you from overheating , this should be safer.

I suggest also to protect Primary (Input) by adding a fuse for 2,75A (Maxi) in case input is 120VAC.

[Paul Adsett]

Thanks for that (as always) good advice Phil. Some of these transformers have built in circuit breaker protection in the secondary 24v line. The addition of a primary side fuse is a good idea.
I am just shocked at how massive and heavy this 250w transformer is!

[Phil Murat]

Woh.........Ok, I have just reviewed datasheet : 18Pounds , so, more than 8 Kgs!!

Sure this is a traditional copper unit.This transformer looks to be sealed, is it possible secondary is protected by a built in Auto-Reset fuse for exemple ?

If size x weight are not compatible with user needs , I assume it is possible to change for an Electronic Power unit.
An other interest of an Electronic Power unit is output voltage can be slightly adjusted so that it is possible to reach 26V to boost the bulb a little.

[Paul Adsett]

Are you thinking of a switching power supply Phil? Are these suitable for halogen lamps, I see them for LED lighting applications. Please send a link to something that you think would work.

[Dominique De Bast]

FFR, in Germany, converts GS 1200 projectors to a 250 watt lamps, I beleive they use small transformers. They are on holiday at the moment and their site is closed until they come back (as always when they are not open).

[Phil Murat]

Yes, switching Power Supply, this is something which is supposed to work for miscellaneous purposes. However it needs to be vented properly :

https://www.amazon.fr/Alimentation-T...dp/B077CK3NXY/

(This is in French language, this one is ok for 600w)