www.diycinema.co.uk

[silverdollar_uk]

Hello Everyone!

Is there anyone here!! Ok just want a few opinions, I am going to retrofit my OHP but i am unsure whether to use a 250w or 400w HID setup. In both instances i plan to use the doubled ended HQI-TS bulbs. I don't think the dimensions of these bulbs are too restrictive, being 163mm and 206mm in length respectively. But i am concerned that the heat from the 400w may be too great and unsafe in a smallish enlcosure like an OHP. I do know that my 240w halogen gets damn hot, probably not as hot as a 250w MH but how does it compare to a 400w setup?

I look forward to any suggestions!

P.S. Anyone know of a cheap supplier of 32uF/250v lighting capacitors?

[kingmully]

this is exactly what i did, i first fittef a double ended MH lamp which was super, but it the died, so i had a spare 400w longer bulb hich i the sqweezed in the ohp.
my opinion is that the long lamp would just about fit like mine did but only i a diagnol position.

i later decided to buld a projector 15 inch casing because the ohp casing was made out of metal. the ohp gets really hot but the fresnel can take the heat. but i wanted to be comfortable so i built a box with the parts of the ohp.

once again i recomend a double ended lamp of 250w because my ohp got real hot with a 250w ballast fitted to a 4oow lamp.
i also tried to buld a heat shield in the ohp but with the casing being all metal after 20minutes the heat get conducted all around.

if ur sticking with the ohp desighn allow cool air to enter from the top or the lid as it cools the lcd and fres lens,
cheers
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hi

[silverdollar_uk]

Thanks Kingmully!

It seems that the 250w setup may be my best bet then, did you get a noticeable improvement in brightness with the double ended MH over the halogen? Do you have any pics

[doug]

Hey mate, sites been very quiet recently probably due to all these new cheap projectors you can get!

250W Metal halide will give out roughly the same amount of heat as the halogen lamp, so cooling wise you shouldn't have to do anything but you'll get about 3 times as much light output! Sounds like a good choice to me. 400W will definitely need extra cooling in your OHP.

I've got 400W lighting kits if anyone needs one, won't be much either, about £15 + £10 delivery and includes capacitor and igniter but no lamp. There are some pics in the for sale section.

One thing you have to watch out for with metal halide is the UV. A normal halogen lamp doesn't emit too much but metal halide lamps do. The Fresnels will probably absorb most of it. The glass plate on the projector should also absorb a bit of the high energy stuff but you should really think about getting a filter. I used palram 'palsun' polycarbonate on mine.

[silverdollar_uk]

Hi Doug!

Well I've just bought a 250w ballast inc. Cap and Ignitior in a metal box, one of those budget boxes you see in Hydroponics shops, bit of a gamble hopefully i can use HPS and MH with it, only 15 quid delivered so we shall see.

On a side note, i almost bought a ballast and ignitor separately, but it needed a 32uF/250v cap which is quite difficult to find, what would happen if i used a 33uF or 30F Cap given the tolerance levels should cross the 32uf mark?

Another thing, the bulbs of choice nowadays appear to be the ceramic Philips CDM-T and Osram HCI with their shorter arcs higher lumens and higher CRI. Better for PJs than the older HQI style technologies. However, they "require" ballasts fitted with thermal cutoffs to use them, since they draw a lot of current when they are approaching the end of their life. However, such thermal cutoff ballasts are only really required when you are to leave the lighting system unattended, provided i can spot when the bulb is dying/dimming whatever, then there shouldn't be a problem, same with timed/untimed ignitors, or am i way off base here?

Oh yeah, i've been searching for faulty projectors on ebay recently always seem to get outbid....wouldn't be you would it!

[doug]

Hmm.. i haven't really bidded much on faulty projectors recently, nothing's really caught my eye! You'd know it was me though by the name!

Still they are some great deals to be had on ebay. The CP-SX5500 i posted a repair of is my all time favorite projector. LCOS really blows everything else i've seen away and the whole setup cost about the same as my first DIY pj!

Sounds like a nice cheap deal on the lamp!

I am sure you would be fine with the capacitor, like you say, things like that are made to a fairly low tolerance so it should still satisfy the manufactures spec.

To be honest i haven't kept up with the latest lamps people are using as i've been using commercial lamps ( i got lucky and won a large job lot of 'faulty' lamps off ebay which are mainly fine!! )

I see your reasoning with the ballast but i wouldn't like to say one way or the other. It sounds like a step in the direction of the electronic ballasts used in commercial pjs which have a lot of control over the lamp.

What did interest me were the lamps YWH was selling on diyaudio. I'm not sure if you saw them but if you can get an old ballast out a projector and order a lamp from him you've got a really nice small arc setup just like in a real PJ. Great for retrofitting or repairing old lamps as well! Problem is it can get expensive!