Projector so far,
LCD: Samsung 15.4" Wuxga 1080p
Controller: Pixelworks from an old johnzo1995 group buy
Triplet: 18" Beseler
Fresnels: 220/550 UnSplit
Ballast: 400w M59 Sola, Now Overdriven to ~450w with extra 2uf Cap, heat sink, & fan.
Bulb: 400w T-15 6500K 95 CRI
Reflector: 68mm Cold Mirror
Lexan UV shield
FS Mirror cut from an old CRT RPTV
Modded ATX power supply
Attic fan thermostat

Here are some work-in-progress pics.


This style projector was seemingly wrote off a long time ago without much explanation. One tester stated discoloration on projection caused by the salts in their 400w lamp settling in the light path of their bulb towards the LCD due to gravity.Another confirmed it and that was it. The problem is that there is no pics or more discussion of this problem. No one else ever complained about this that built one, other than these two. Most people who started builds after this had everyone point this old info out and were scared off before completing their invert verticals.

Now I admit it sounds bad, but how bad is it really? I figured I would try it out, and find out for myself. There is a minor color shift of a few degrees to the warmer. How minor? Well, my camera won't record it, and my wife just says, " Where... where.,, I can kind of see it I guess, can I go now?" Lets say <200k just to be safe. Nowhere near the difference of overdriving to 450w. The "metal salts shadow" affects about an 16+:9.25 area. On a native 4:3 LCD this would be a very big deal to me. With a 16:10 15.4" LCD it is only noticeable on pure white screens when you are looking for it, and when used at 16:9 (centered) it might as well be nonexistent. This is also with only a 220 fres. I don't think you could use a condenser lens in this configuration. A reflector is also a must. 15.4" 16:10 and smaller LCDs, no >13" 4:3 LCDs.

I have also experimented with overdriving these bulbs, and found 450w to be the best choice. At 500w there is a very BIG jump in brightness and reds, but yellows become very orange tinged, enclosure temperatures jump way up, and worse the deep blues are gone replaced with a kind of pastel awfulness. If you are familiar with Sesame Street Grover's color is the same as Herry's at this level. 450w gives you a small brightness bump, blues stay blue, and you get much better reds. This really improves skin tones. The slight drop in color temp also shifts the big orange MH spike a little closer to yellow, this give you better red and orange contrast ratios. I've tried this with three different identical bulbs with ~200hr, ~800hr, and a used bulb with over 2000hr.

The only screen pic I have right now is from a bedsheet I threw up on the wall until my BO cloth came in. It was a little too transparent.



This is strait 480p on a 130" 16:10 "screen" 400w.

The BO cloth looks a lot better, and brighter. I'll post some pics in a few days before I take it down and put the final screen up.

I'm in the middle of building a high gain Silver PVC torus screen at 115" 16:9. I have it up flat right now over the BO cloth to stretch the wrinkles out. It looks like I will end up with a gain of around 3-6 with no noticeable loss in black levels. Here's a preview.


In room the bottom looks like the top and the top hurts your eyes.

They were trying to use this material with CRT projectors back in 03, but found the gain was to high and cause too much color shift. Luckily, single lamp projectors don't have color shift issues.

neat , this is the first inverted vertical build i have seen

good job

I like the vertical build and the T15 is a nice CRI lamp too.

It does look like a slight over drive is all that most lamps need or want before the colors start to shift.

Not all the lamps have a salt problem and as they age some of the salts get used so I'm glat to see someone trying the vertical idea again there is a few advantages like having the heat go up and away from the LCD which is a bit of a problem with the 575 and 1000 watt lamps.

If the salts are not much of a problem with your setup I don't see why you could not use a condenser lens. Some of the lamps do burn really clean with no salts after warm up.

How have you measured the color shift?

Did you cut a hole in the roof?

jeffek, Thanks

AV,
There is a hole in the ceiling. I have a three foot crawl space between my 1st and 2nd floors, so I decided to vent the projector up there. The cardboard is going to be the template for the finished wind tunnel. The PJ is sealed like normal with an exhaust fan pulling air out. I cut a hole in the ceiling and installed another 120mm fan above the PJ exhaust. The cardboard is designed with two air vents at the back which are unseen, and prevent light leaks. The ballast with heat sink and fan is located near one vent on top of the PJ. Since the ceiling fan is not run under pressure it pulls more air than the PJ fan, so it pulls cool air in through the air vents to help cool the exiting PJ air before getting trapped in the crawl space.

I compared the color shifts using a complex mixture of a computer with dual monitor capability, a calibration disk with color filters, a couple of now dead light switches, LCD controller card with multiple savable settings, time, sun glasses, oven mitt, a color wheel, time, and a lot of Sesame Street DVD frames.

I can't tell you the exact temp k change. The metal salts effect is about half way to what I got when I added 50w, so using the numbers you found from OSRAM I just guessed it was <200k. I figured this out by turning the bulb to get the salts out of the way. I could get about 30min before they started to creep back around.

I could possibly use a condenser, but I believe the way it shapes the light it will shrink the profile (top to bottom on wall) of the shadow making it apparent onscreen. This is why I am experimenting with with DIY high gain screens, which make a condenser less needed.

Top SPVC material not tensioned, thus waves.


I did forget to add that this is with extended on times. If you just leave the lamp on for an hour of two a day the salts build up and start turning more and more thick and yellow. A good 8hr or more burn is needed every few cycles to keep things powdery white with small yellow balls near the electrodes it seems.

Too much heat also increases the amount of the yellow salts, fast. If you start seeing little black (not gray) pieces of round grit mixed in the yellow, the bulb is not going to last to long. Starting problems will be the first sign. If you keep running the bulb without cooling it down somehow, the mercury that should pool around the electrodes will leach off onto the side of the arc chamber and short it out. Ask me how I know...

Hi Soho

I'm new to all this, but I've spent the past few months collecting parts and planning my design..... It just so happens that an Inverted vertical suits my final resting place for the PJ and after hours of designing I was happy with the overall look and build-ability.

Then I discover there could be issues with this orientation..... I'm glad someone else is currently building this style and I'll keep an eye out for updates as any info on the pro's and Cons could save this Newb a great deal of hassle!!!

Give me a little time and I'll do a write up of my build with pics, measurements, and a few of the things I would/will do differently.

You may want to consider a ceramic MH if you're experiencing shadows/ghosting from salts. I used a Ceramic 150W in my inverted build. No issues.

No ghosting, just a minor color shift "shadow" to the warmer side visible at 16:10. With my 15.4" in 16:9 mode I have no issues.

Getting there...

The Fifth Element DVD 480p

OK, as promised here is a series of pics with measurements added. These show the modifications I am going to make to change from a side air intake to a front intake for improved air flow.

I have zero LCD cooling problems now. The LCD registers about 5deg over ambient. The sides of the light chamber just get a bit warmer than I would like at 450w. At 400w there is no problem, other than I would like to put the fan on the intake side to pull more air over the reflector. This is what the extra 80mm fan in the pic is for. It was a mistake., I was in to big of a hurry to finish with the router that day.

Getting closer...

The Fifth Element DVD 480p

Switched to a 6 gain screen, so I'm having to use different camera settings. The new pic washed out if I went any higher.

Here is an example of the difference between the new screen and BOC.

That Fifth Element shot is a pretty amazing picture! Kudos to you!