Sorry to slip off-topic a bit, but it seems a lot of 575watters read this thread so...

Is anyone getting a pinprick hotspot in the center of the screen? I know most are going split to dampen the glowies, but I need to go unsplit for a couple reasons and I can't seem to find any suggestions for taming the hotspot other than going with split setup.

I'm curious, ignorant, and inexperienced. Deadly combo. But when you say pinprick you mean like the size of a dime on the projection screen or what? (I'm toying with the idea of having a stab at a 575 someday so am following along.) I won't be going split unless absolutely necessary so this has caught my eye. Would maybe slightly misaligning the optical centers of the fresnels have any effect at all on what you are seeing/describing??? Just a thought.

Edit: With the gains realized from the 575 one could also "dodge" the hotspot.

Yes, dime-size is about right. I've tried misaligning the fresnels, and moving the reflector further away. Both seemed to lessen the problem a bit, but not solve it outright. I guess more experimentation is in order. I last saw this problem in my first noobie build, when I simply slapped a LCD on top of a 575w OHP. I read about it back then over at diyaudio, and everyone reporting the problem was also using the 575. They all said going split was the answer. Problem is, a split setup magnifies my projection too large for my screen and my PJ placement is pretty much locked.

p.s. the hotspot became significantly worse after I introduced the condenser.

So what about dodging it then? Has anyone had a go at that solution? Think you might make that work for you?

Even after two cups of coffee I can't quite wrap my head around what you mean by "dodge". Turning on room lights a wee bit does help keep it from being so obvious.

I tried a 575W lamp the other day. I also had this hotspot. I assumed that it was from the nipple on the arc chamber. I had it pointing towards the reflector. I was gonna try pointing it downwards to see if the hotspot went away. Actually that hotspot might just be the arc ! ... in which case i'm not sure what can be done about it....

By dodge I mean placing something into the light path which would attenuate the hot spot.

It's a photographic term whereby one artificially alters exposure or development. The opposite term is burn. I think I got that right.

You need some neutral filter between your source and collimator to darken the bright spot.

Implementation of this idea may prove absolutely impractical.

I actually have a small dark spot, but that is the very center of the fresnel blocking light. It was not noticeable with large arc lamps, but the small arc 575 shows the small black dot of the center field fresnel (unsplit setup).

If you guys are getting the center of the panel too hot, i would reccomend a fan blowing on the panel in the front end of the projector like i have.

My light is pretty even, it is only about 5 lux brighter in the hotspot vs. a few inches away from the hotspot.

The smaller the arc the sharper the arc image and the more any imperfection will be seen.

I had this light pattern before I moved the light back 10mm or so.

http://www.lumenlab.com/forums/uploads/pos...-1159686499.jpg

I then painted a small spot on the reflector so it would not give any gain in the middle of the screen. The final spot was larger about 25% of the whole reflector.

http://www.lumenlab.com/forums/uploads/pos...-1160431689.jpg

It takes a lot of fine tuning to get a even light pattern. I would start by moving the condenser a little further away from the LCD.

With the pro reflector there is no going back. a slight rub on the coating and it will come off but it need to be nice and even.

So shipping to me is like 35 so is this a great deal for the triplet, fres and 575 and bulb for 135 hmmmm you guys need to stop finding stuff but seriously this is a great deal right ?????????? and if I do get it where the freak are the bulbs for it and the price for this 575

Give that man a cigar

For an extremely scientific test, I placed a little piece of popcorn shipping foam in the center of the condenser while the projector was running. Well, I forgot how hot it gets and the foam promptly melted, but once I stopped seeing spots I saw to my surprise that it did in fact attenuate the hot spot. Not entirely, mind you, but enough for me to stop nitpicking for a while and at last place my build in the completed section.

There are several reasons for the spot.

The first is the nipple of the lamp. it needs to be pointed up or down , and not forwards or backwards.

The second is with such a nice bright light you will see the small center spot that is formed at the center of the fresnel when it is made. On some fresnels it's worse than others. That is why going to a split setup gets rid of it.

The third is the Lcd getting to hot. Proper cooling is a must.

Umm . . . would you mind . . . I mean . . . well, how's about a lithe and supple - and very flexible if possible - errrr . . . never mind.


It didn't cause a mess??? I hope not!!! Sorry sensi!

Click to view attachment

Drinking straw?



It did cause a mess but that's my point. The goop seemed to help, by making the dead center of the condenser slightly more opaque.

I guess the straw will have to do.

You're going to leave the goop? Wow! Well, that's cool I guess. But I'll bet you no one else uses your technique.

Forgive me but I'm very spatially challenged. Because my build is vertical, "up" and "down" are throwing me off. By forwards or backwards I'm assuming you mean not obstructing the arc or the arc's reflection? Or the opposite?

Exactly

OK I officially HATE 575 watt ballast

I was working on my Ask 880 today putting on a shower drain focusing mechanism for my 220mm triplet. Spent 2 hours perfecting and painting it and then went to test it.

5 minutes of enjoying my success and pop, there goes a fuse. So I replace the fuse with another and pop there goes the ballast. Smoked up my theater room too. The sad part is I didn't do anything to the projector yet other than add the 220mm lens. So theres no way it was an error on my part. these 575 watt ballast are just to damn fickle.

Guess that project is shelved for a while.

Dam, this is not good news for me since we pretty much have the same ballast make. Sorry to hear this jonjandran, think the lack of the EMI filter (and again, I'm not sure if you had it place) could have anything to do with it blowing itself up? Seems a magnetic core is probably the best way to go seeing that they are built more ruggedly than these electronics as I have seen. Problem is they aren't very efficient especially with power usage.

Nope this was the Ask 880 I have. It's still factory , I haven't modded it at all. Original Eballast is in it with all original parts. All I did was add a triplet because I bought it without one (it was mia).

It does look very similar to the Proxima Eballast, in fact I would bet it's made by the same company. It even has the 400w dimming feature.

I guess after 10 years they just wear out

Hey,
Do you think if I kept my 575 ballast with on the 400w dimming feature on all the time it would help me ballast last a little longer. I would hate to waste all those lumens but I just can't have mine blow every 5 minutes like everyone elses.

Sorry to hear that, man. If you're up for it, take a look at the capacitors. One of mine blew in my Dukane 680 ballast. Replacing it brought the ballast back to life. Just a thought...

Yeah, I read on a couple forums that the main thing that blows on these units is the capacitors. They may be relatively easy to fix.

I'll take a look at it today then

Well, I spoke too soon. The center hotspot is back. Maybe the goop burned off the condenser. Thing is, I'm fairly certain it can't be explained by any of jonjandran's reasons (the nipple is out of the arc path, lcd is not overheating, and the spot is a bright point, not a shadow reflection of the fresnel center). No way in hell I'm going to try to spray paint a perfect black circle on my pro reflector, though I wonder if some kind of circular sticker or even a coin might work?

I guess these 575w lamps (and their ballasts) are turning out to be more problematic than we thought...

I'll get a photo of exactly what I'm talking about sometime soon.

Try hi-temp paint on the condensor? At least that should be easily cleaned with some "Goo Gone" or similar.

Well that idea is a bust.

The Ask 880 575watt Eballast is epoxied in on both ends and probably throughout the whole thing. What a stupid thing to do

Well, here's the thing. Any outright obstruction on the condenser creates an equally annoying dark spot. What is needed is something that is just a wee bit more opaque than the condenser itself. This afternoon I actually tried applying some glue from a glue stick, then I "diluted" it a bit with some goo gone, so a thin film was left. It worked pretty well, and dimmed the hotspot to a fairly acceptable level. Unfortunately, it also dimmed the area around the hotspot, so I'll have to keep playing with it.

If I knew for certain that the reflector is contributing I would explore "dodging" that as well, but it's a whole lot easier to experiment with the condenser without doing irreversible damage.

Dang . . . touchy, touchy procedure. In the past there have been suggestions regarding using a heat fusing transparency sheet run through a laser printer (the kind used for lecture overheads) which had been grayed out appropriately by the following method. Take a screenshot of a white image from your projector. Process it to enhance the vignetting to get a visual handle on just what's what. Use that image to print out a "filter" of sorts to darken the light areas. Place the sheet in an appropriate plane in the light path. I know it doesn't sound much more appealing than what your doing maybe but it's just some food for thought.

Ok, as AV suggested, it looks like dodging the reflector is turning out to be the best course of action for dimming the pinprick hotspot. I popped a nut in the reflector (and yes I know how that sounds) as another experiment and that cut the spot quite a bit. Next I think I'll try painting a coin with high heat black. Still not inclined to try painting the reflector itself just yet, as even if I managed to do it perfectly, it seems to me that having something metal absorb the heat would be better than super heating one spot in the glass.

i know why my hotspot is minimal! my reflector is offset about 1 cm. try it see if it helps

Does anybody know whether a lamp can also flicker towards the end of its life? As if the hotspot wasn't a big enough pain, my lamp started flickering over the weekend. I noticed on one of jonjandran's ASK retrofit thread that flickering presaged a ballast meltdown. I'm praying its the lamp and not the ballast.

If you mean off-center, I'm SOOL on that because my reflector is JB-welded to the fan guard, and the fan guard is centered by default on the all-thread.

Maybe a crinkly circle of foil would be good to drop on that reflector? Or even the foil lightly spritzed with some hi-temp black paint?

So far I haven't seen a suggestion to move the reflector back a tad, the down side is - might cut down a bit on brightness.

Well, I've actually tried that already, but I guess I could always go farther.

If you look at the lamp reflection from the front triplet (with the LCD removed) you will be able to see two images one from the lamp and one from the reflector. If the reflector is too close the image will be larger than the real lamp image. It is hard to see the reflector image if it is smaller. This is with the power OFF!

The arc does curve up slightly so it may be better to move the lamp down 1mm or so.

I do all my adjusting with the lamp running which is vary dangerous. (radiation burns and electrocution hazard) First with the reflector set way back and after the lamp and condenser is at its best add in the the reflector.

I would mess with the reflector last. Just remove it if you can or place some black high heat painted foil between the reflector and lamp. I still thing the lamp and condenser need to be further from the fresnel.

You don't need to paint the reflector just rub off the coating. I would do last. There is no going back.

Thanks for all the suggestions, AV. I have been trying to do small adjustments with the lamp running, but the soreness in my eyes is beginning to worry me a bit. I've tried all kinds of things -- removing the reflector entirely, removing the condenser and putting the lamp at the rear fresnel's focal length again, keeping the condenser and not moving it forward at all -- and though all dampened the hotspot to greater or lesser degress, nothing really fixed it entirely. It's beginning to drive me a bit batty, actually, to the point where I am seriously considering going with an Ushio 400w or something else. Maybe I need to try another rear fresnel. I guess that only other thing left is to try split setup again, but that introduced a light ring related to some small leakage around the condenser.

Let this be a lesson to all those who dare put their projectors in the "Completed" section -- you are just damning yourself to a perpetual limbo of nearly finished.

You're just trying to make us fence-sitters feel better heading into the holidays! Honestly, it's very refreshing to hear you say that.

I just got mine fired up again and although I've been really thinking about the 575 it just looks so dang good with the 400 that I may put off pursuit of more wattage. Then again, mdmfootball does have that sale currently.


Amen to that, brother. Amen!

My 2 cents on this is I've tried the 220mm fres on 15" panel using a 4.5" x 6.5"fl precon. Couldn't get coverage enough with it but when using a 5"x 12"fl precon I was able to, however, vignetting was really unacceptable. I found there was more brightness towards the middle than the corners and this was while using a 400w'r. When using a 317 or a 330mm rear fres with the 4.5" x 6.5"fl precon the spread was dam near visually perfect with the brightness blending better to the sides and corners. So I can imagine what would happen when using a higher wattage lamp like a 575w and it's shorter arc. The center must be pretty intense on screen as what you found in your situation. I'd say, based on my experience and NaturalNewb's 575w build (which he found worked best for him) you might be better off just changing the rear fres to one of the 317's or 330's.

Thanks for the input, Sim. I've actually considered this, and have a 330 cut and ready to go. I'm just afraid I might not have enough room in the enclosure.

Hey NN,

If you have a minute, can you chime in with your current lamp>precon and 6.5"FL precon>330 fres distances. I found some in your PLOG, but I think they were related to the Ushio lamp and/or the larger condenser.. Thanks.

ya that was for the ushio and the larger condenser.

tonight or tomorro i will put the distances in my PLOG, ill send you a PM when i get them posted!

Not to add fuel to the fire or anything.....

http://cgi.ebay.com/Dukane-670-Overhead-Pr...ksid=p1638.m118

http://cgi.ebay.com/Dukane-680-8000-Lumen-...1QQcmdZViewItem

http://www.ddav.com/used_equipment.htm (Dukane 680)

Well, for the record, I'm relatively confident I have isolated the pinprick hotspot, or at least its seemingly extreme manifestation in my case, to a small raised bump in the very center of my 220 rear fresnel. I tried a 330 and a 200 today, after checking that neither had the same kind of tiny protuberance, and the hotspot was significantly lessened. More so than anything else I've tried anyway. Unfortunately, a downside of their brightness is that these 575watters pick up any flaws in your fresnels. So if you plan on using this bulb, take extra good care of those fressies and hope they arrive without any flaws from the factory.

p.s. apologies to all concerned for this small thread hijacking...

I don’t think it’s the brightness that shows up flaws in the fresnels but more the arc length.

Try holding your suspect fresnel near to the projection screen so that its image is projected onto the screen, hold it somewhere with in its FL. This will show all the flaws you’ll even see them in 3D if you angle the fresnel.

I'm installing a 575 ballast from an Elmo Solar Delux and had some questions. Figured this is as good a thread as any to ask. Hopefully, lots of 575 users out there that can give me a clue.

In the past, I've calculated roughly that a 10% decrease in power for a lamp increases lifetime by about 2 times. This is a rough calc, but it makes sense to me. So if I drop the power of my ballast from 575 to about 400 using the low power mode I should be able to increase a 750 hr lamp to about 750x2x2x2=6,000 hrs. this is about perfect for me (if it works) because it would mean buying about one lamp per year.

My question is has anyone seen a significant increase in lamp life by using the low power mode on their 575 ballast? Any anecdotal observations?

In addition, has anyone tried a lamp other than the typical 95V small arc lamp with their 575 electronic ballast. What would happen if we put an HQI in with the electronic ballast. The HQI requires about 125V. Any speculations or experience in this area?

I would be interested in prolonging a 575w'r life to 6,000 from 750 hours but I wonder how much of lumens difference would there be by dropping to 400w. Phutton, I take it your ballast as jumpers for 400w as well?

Personally, I would be a bit afraid to try any other lamp with different voltage requirements on these ballast's. They seem a bit sensitive and have tendency to die unexpectedly. Perhaps a magnetic core instead since they can take a great deal of beating to test with but on these rare electronic 575's?

I have a Dukane 575 watt light engine I will be using in a build soon that came with the high/low switch. So it will be easy to flip the switch and take measurements. But that will be a week or two from now.

Yeah, the ballast I have has a switch that provides low and high power. I assume the low power is 400 watts.

I agree with you. If this were a magnetic ballast then no poblem. But I don't know about electronic ones. Anyhow, the point would be mute if the low power provides 4000-6000 hours. That would mean changing out the bulb only once per year. A typical 750 hour 575 what bulb puts out 49,000 lumens. At 400 watts I would assume a linear drop in output to about 34000 lumens. Not bad, but not great either. You're looking at a decrease of 30% in lumens on screen compared to the 575 watter. By my calcs and typical 575 watt outputs I would estimate about 180 lumens on screen at 400 watts. that's a little better than the typical 400 watt long arclength bulbs.