doozer wrote:

As someone who has worked with optics for projectors, I can tell
you
that it won't work. You need an immense amount of light intensity
and it
has to be focused just so (if you've ever fired up the projection
lamp
with the housing open, you will know just how bright it is - you
can't
see anything else for a few minutes). Many man hours of research go
into
producing efficient optics for the projection beam. The lamps are
discharge (arc) types and have control gear in the projector - you
can't
just replace them with any old lamp.

What you can sometimes do is buy the lamp itself separately, as the

manufacturer replacement often includes the reflector and housing.
This
can cut down the cost considerably. Find the manufacturer code from
the
lamp itself and google for it.

Hmmmm, that bodes badly then.

The bulb and reflector come as a single unit (see links below) so I
imagine the majority of the cost is in the bulb.

a front view of the bulb would have been very helpful.


I can't help getting
the feeling though that I'm being massively ripped off

yep. Always check the run cost of products you buy: I think you will in
future


and its the
housing not the bulb that is expensive. I wouldn't be at all
surprised
to find that practically every Philips projector uses this exact same
bulb.

As for the light being focused. Yep I agree that it is focused but,
and
here's the interesting bit, there is obviously a reflector in the
bulb
but there is also a lense in front of the bulb that diffuses the
light.

Perhaps, but I expect it more likely to be condenser optics than
diffuser. If thats the case, youre fairly well stuffed. At best you
could produce a very dim image without that bulb.


I am wondering just how accurately I would have to mimic the real
bulb
to get a good solution.

Quite likely youd need the same intense small spot.


I think there might have been a slight misunderstanding as well. I
wasn't intending to just stick a low voltage halogen into the hole
occupied by the PJ bulb as I realise that wouldn't be even close to
good
enough and wouldn't work anyway.

I'd try it, not very optimistically, but it might. The control gear
might assume its started and run the thing ok, and the central element
might be adequate to get something out. Might be your best shot, even
if not a very good one.

Youll need to match run voltages tho. Not sure what that one is, the
1=2E6kW Beck carbon arc I used was 40v 40A. sci.engr.lighting should be
able to give you more info on this bulb and any possible solutions.

If you get a dim image that way, you can then max the power out as much
as poss with an external supply, adding heavy forced cooling to avoid
meltdown.


I was thinking more like a dozen in an
internally mirrored and forced air cooled box that sits under the
projector with a mirror array to take the light into the PJ. Surely
that
would be bright enough!

if you can direct it all onto one spot, sure. Maybe you can do that
with mirrors.


I would probably be looking first at a legal solution. I would argue
that =A3450 for a 10 hour lightbulb, if its an essential spare part
supplied only by philips, was unreasonable. There is a law against
unreasonable prices in UK, but it is only invoked in cases of wild
excess, but I would think this does come into that category. Its
=A345,000 for 1000 hours of light. Compare that to a 1000hr GLS at 20p,
or a 2000hr halogen and =A31.

I would also consider contacting the mrfr, giving them an opportunity
to refund the goods cost, pointing out that you will be a publicity
rampage if they dont. Not much chance of them doing so, but it shows
youve given them a chance to resolve the situauion

Ianal tho, and wouldnt be surprised if you were right out of luck.

That is, assuming you dont want to build a carbon arc light... they
dont last any longer, but are way cheaper.


NT