DIY Projector Lamp

[doozer]

This maybe a little off the normal beaten path for this group but it has some knowledgeable people and this certainly falls into the category of DIY. I have already asked on AV Forums BTW.

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 . 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.

[BigWallop]

What voltage does the lamp take? I know the projector needs something like a 250 watt UHP lamp, but you don't give a voltage, which would help. I know of a few places that will sell you lamps of that wattage, and a whole lot cheaper than the price you quote in your post, but I need to find out which voltage is needed to compare their prices for you.

They will deliver directly to your door as well.

If you get a lamp of the same brightness and focus quality, then it might just be a case of adapting the little housing that holds the lamp in place on the projector.

[Tim Mitchell]

In article , doozer writes

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.

[doozer]

Ok, so not quite everyone thinks that I am mad which is a good thing. I have checked out the manual and no joy on a voltage. Can anyone tell what it might be from a couple of pictures?

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

Thanks.

[Lee]

In addition to the other points mentioned, you will probably find that the logic control system of the projector will not allow it to operate with no/or a defective bulb.

If you *can* just replace the lamp itself, that should be cheaper than the whole housing.

Lee

[BigWallop]

It looks like it is a 12 or 24 volts lamp, but I couldn't be that sure which to say it is from the pictures.

Try contacting these people

for more help on this, and as Tim has said, ask if they do the lamp separately from the holder.

These people are always helpful and give the best advice on these types of things.

[doozer]

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. I can't help getting the feeling though that I'm being massively ripped off 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. I am wondering just how accurately I would have to mimic the real bulb to get a good solution.

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 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!

[BigWallop]

And bloody hot enough as well. Forced air cooled? You'd need to dip the fans in a bath of cooling oil to keep them from melting, mate. :-)

[bigcat]

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

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

surprised

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.

Quite likely youd need the same intense small spot.

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.

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

[Martin Angove]

Many lamp replacement "kits" also include new (air) filters and possibly other bits, so you have to include them in your comparisons too.

Went through this loop a few years ago with bulbs for NEC and BARCO projectors. The Barco ones were £450 and had a rated life of just 720 hours. You could reset the warning up to 750 hours but after that the projector put a big banner over the screen until you entered the serial number of the new bulb. Actually, any old number would do, but since these projectors were well over £15k new we didn't chance it.

We discovered that both the Barco and the NEC lamps (IIRC, certainly the Barco ones) were simply re-packaged standard Osram bulbs, but at a higher power rating than available through any of the usual outlets. I forget the specifics, but we could get the bulbs up to (say) 250W, and the Barcos needed 400W which were only available through Barco. Again, needless to say, the bare bulbs were a fraction the cost of the replacement lamp assemblies.

Eventually we managed to bulk-purchase the bulbs (we had 12 of the Barcos IIRC, on 8+ hours a day) and got them at £250.

The NECs were better at £350 to start with (they came down too) and 2000 hour life. We had 16 of those.

*If* we could have got hold of the right sort of bulb we would have tried it, BUT:

The additional problem with the Barcos was bleaching of the dichroic filters. No, I don't know how you can bleach a diffraction device either, but they seemed to do that quite regularly, especially if the projector had been apart for any reason (cleaning beyond the air filters for example). It is just possible that if it wasn't put back together absolutely perfectly a "hot spot" would develop. The dichroics were £150 each, again IIRC. With a DIY cobbled-together lamp assembly I suspect that the problem would have been even worse.

This is still a problem with projectors. Yes, you may be able to get a basic SVGA model for £500 from the right place, but if you are doing more than watching a couple of hours of television in the evening you really need to think about the running costs.

Have you ever *seen* the light from a discharge lamp? Ignoring the problem of UV exposure (they produce gallons of the stuff) they have to be the brightest source I've seen, Watt for Watt.

Hwyl!

M.

[Adrian C]

Just thinking. Do white LED's yet come anywhere close (even in an array?)

[doozer]

I did think of white LEDs as you can get extremely bright ones (used mostly on the tips of plane wings I believe) but they are even more expensive than the real thing and also don't last that long. A large (maybe even huge) array of small white LED's might work but I am not sure it would be that cost effective as they fail fairly quickly if they get hot. I think the cheapest solution is short florescent tubes. I could probably pack quite a few into a small area. Another possibility is just powering up the cheapest projector bulb money can buy. I haven't really decided because until I know how to get the projector to come on without a bulb in place the whole things a bit moot.

[doozer]

These bulbs, LCA 3111 for the interested, last about 1500 hours and I believe they are now out of production so I don't see the price coming down.

This projector have already been through two sets of analysers and polarizers for the blue and green channel but they were replaced under warranty (the parts are about £20). After the second change though something was different (the projector was much cooler) so I assume the guy who replaced them did something else as well they he didn't report.

We only use it to watch a film 3 or 4 times a week (tops) so the bulb has lasted about 2.5 years. Even so I still would much rather not have to shell out £450 as I am sure you understand.

Just seeing the amount of light that comes out the front (and back) tells me it's extremely bright. At least my solution would probably have less UV which should help the projector last longer.

[dennis]

Discharge lamps are about five times brighter than the equivalent fluorescent tube. Just imagine 200W of tubes in a 1" cube.

[Andrew Gabriel]

I don't know what sort of lamp this is, but if it's a short arc HID tube, it is started with a very high voltage pulse (many 10's of kV) which is a safety risk. Also the bulb itself is pressurised even when cold and will not just break, but will explode if dropped or scratched, and you should be wearing eye protection whilst handling it. If you damage it in handling, it can also explode later when running (at even higher pressure).

[Ian Stirling]

They are about as efficient though, the source is just much smaller.

[Ian Stirling]

But. IIRC, the luxeon 1W chips are about 1.5mm^2. That's about .2W power, when you compare it to a discharge bulb, as it's much less efficient.

1.5mm*1.5mm means you get about 36/cm^2, or 8W equivalent. Some new 'vapourware' LEDs claim about 3 times that, or 24W/cm^2, but that means a source size of over 3cm diameter to hit 240W. And if you're doing it at all, you probably don't want to use white LEDs, but work out some way to do it with RGB ones, and eliminate the insanity of wasting 2/3 of the light on a filter wheel. And the other problem I glossed over is that LEDs need kept well under 100C to function. The discharge bulb will be quite happy at a wall temp of 300C. And, with the better part of a kilowatt going into an area smaller than the contact patches of some CPUs, thermal design is going to be a real bitch.

[BigWallop]

It is under pressure Andy, that's what the UHP stands for on the lamp. It is Argon gassed to quite a bit of pressure in fact.

[Martin Angove]

Been there, done that. At the same place where we had all the video projectors, we also had some theatre-type lamps. The Mac2000s (robotic lights) had a very bright discharge lamp, but unlike the projectors, they didn't have an automatic timer-based safety cut out. Result (before I got into the habit of logging every bulb change) was that a bulb exploded inside one of the projectors, destroying the ceramic lampholder, rear reflector and (inch-thick) front lens. Bits of glass got into the rest of the projector and caused damage to servos, wiring and electronics. You can imagine the repair cost in parts alone.

The other thing to note with these type of lamps, and with other high temperature lamps which often have quartz-glass, is not to get fingerprints on the bulb. I hate to think of the mechanism, but it seems to soften the glass around the grease mark, causing the envelope to bulge and thin and eventually break.

Hwyl!

M.

[Tim Mitchell]

In article , Martin Angove writes

It just creates a hot spot because some of the light is absorbed by the fingerprint. If a lamp does get touched you can clean off the fingerprint with an alcohol wipe (before firing it up!) to prevent any problems.

Regarding the original question and having looked at the pictures, the reflector, lamp and housing look like a custom part. I don't think you would be able to get the lamp bit separately. Have you tried googling for the lamp code?