Panasonic PT-L595U Retrofit - diyAudio
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Old 18th June 2004, 01:12 AM   #1
diyAudio Member
Join Date: Dec 2003
Location: Toronto
Default Panasonic PT-L595U Retrofit

Hey guys, new here so please take it easy...

I have a read a bit and thought of building from the ground up but decided against it. So here is my situation.
I bought a Panasonic PT-L595U projector for about 80 bucks on Ebay knowing damn well I might be throwing it out shortly. Since recieving it the lamp is shot and I the initial (what I bielive was a UV filter) is busted.

First off UV filter, to confirm if I hold this square piece of glass to the light and move it around the reflected light is violet and the passed through light is green at a 45 to the source. If someone could confirm this is only a UV filter I would appreciate it.

Second busted lamp. Well I will not be spending $500.00 to replace it only to find out the LCD's are no good. So reading the specs I have found out it is a 280W DC MH lamp, I have finished dissambling the dichroic lense assembly away from the actual lamp and saved it for future use. Now I work at a major electrical distributor and lamps from any of the majors is no problem for me to obtain.
Lamp problem one. I deal with lamps everyday and I have never seen DC refered to in a metal halide as it usally stands for double contact bayonette socket, but in this refrence it is refering to DC power. So a litlle concerned this was some special lamp I looked into MH ballasts and driving the lamps with Direct Current. I discovered all electronic MH ballasts used DC and it actually prevents flickering and extends lamp life. So all MH lamps will run on DC something I didn't previously know.
So knowing this I decided to test my projector with some longer leads running to a standard 250W Mogol base lamp. (looked kind of funny) Well what do you know first shot bang up and running. I ran it forr a few minutes a little nervous because the unit had a blown fuse I replaced with tin foil (I know stupid) so I wasnt sure if it was drawing to much current I would have no protection but a decent gamble as that is what a ballast does limit current.)
This is when I learned lesson two abhout these liitle projector lamps and there electronic DC ballasts. I had noticed in the lamp litreaure it refrencing hot restrike with a yes or no column, now I know why. You see MH lamps when hot are a ***** to restart unless you use a couple of spikes of High Voltage to jolt them back into exitement. My standard industrial 250W didn't like this much. So as long as the lamp is cool it should start first shot but don't try to restrike while hot.
So my questions are as follows does anyone know how to disable this hot restrike high voltage module on the ballast? Does anyone know if an HQI lamp can handle such abuse? Thirdly has anyone been sucessfull with this sort of retrofit?

My plans are to bust the end off an HQI (just the porcylin socket and re-insert back into the dichroic reflecter, try to center and affix the way it was. Does anyone know the smallest Arc Tube HQI in the 250w range?

I am sorry if this rambles but I think what I am trying is possible and feasible just need a small not so pricy HQI, some lamp cement (Have to call the boys at Osram to ask what to use) and a little patience.

Any input would be apreciated..
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Old 21st June 2004, 03:11 AM   #2
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Join Date: Jan 2003
Location: UK
greidy78, there was a post ages ago from a guy who retrofitted a sony LCD projector with regular Halogen 150w bulbs, so (if what I believe you wish to do is to replace the bulb with an inexpensive bulb) it is possible. The biggest problem is to 'trick' the projector into thinking that the original bulb is still inserted and is still working, so the projector will function correctly. As I seem to remember it was a case of shorting out a resistor, but it may be different for your projector, guess it's a case of looking at the circuits. The other problem is that projectors have built in compensation for changes in lamp output, e.g. when the lamp is new the projector recognises this and increases the contrast electronically and decrease the brightness of the individual tft panels accordingly, and when the bulb is getting old, they reduce the contrast and increase the amount of light than can pass through the panes ( I hope that is clear-ish....basically the projector compensates for changes in brightness of bulbs over their life span...) But I doubt that would in reality be a problem for you, assuming you can trick the projector into thinking the original bulb is still there/working.

As for the filter, if there is a greenish colour than it sounds like that is def a UV coating on it.

As for retrofitting a bulb into the projector using the same ballast, my understanding (any one feel free to correct me!) is that ignition voltage varies considerably among 'original bulbs' used in LCD projectors, so I would guess you would not be able to use another MH bulb without modifying the ballast.

As for $500.00 for a bulb, are you sure it is that much, I know most shops quote huge prices for a replacement bulbs as they don't ,make much money on projectors so they think they can get away with charging stupid prices for bulbs, but that does seem a little excess, I know here in the uk, when it comes to bulb prices, you can usually haggle them down considerably, e.g. at least 50%! The problem with bulbs/projectors is that in reality most projectors in commercial environments brake/become obsolete and are replaced long before the bulb goes, e.g. for example at many universities the projectors is usually replaced a long time before the bulb goes so demand for bulbs is actually quite small and if treated well, e.g. the air filter is replaced regularly and the projector used for a good period of time, e.g. 1/2 and hour at a minimum the bulbs usually do last a lot longer than the stated rated life!

Sorry iv'e ranted on a little long, but it is possible to use a different bulb in a LCD projector assuming you can trick it into thinking the original is still there and working, I will have a search on the internet for a link to the person who converted his sony projector that I have in mind....

Hope this post helps a little......

My sugestion would be to work out how to trick the projector into thinking the bulb is still there/working and replace the bulb with say a 250w halogen with a cold mirror or a 250w MH bulb with a seperate ballast.
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Old 21st June 2004, 12:06 PM   #3
Dazzzla is offline Dazzzla  Australia
diyAudio Member
Join Date: Mar 2004
Location: Australia
First off UV filter, to confirm if I hold this square piece of glass to the light and move it around the reflected light is violet and the passed through light is green at a 45 to the source. If someone could confirm this is only a UV filter I would appreciate it.
Hello greidy78

The projector you own is a 3 LCD type. That piece of glass is probably one of the dichroic filters which passes green and reflects the remaining light on to another dichroic filter to separate the remaining two primary colours.

have a look here

hope this helps
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Old 22nd June 2004, 12:29 PM   #4
diyAudio Member
Join Date: Dec 2003
Location: Toronto
Thanks guys for the posts!

With the help of DiyLabs I was able to trick the projector and power up as usual.

As for using the internal ballast I have decided against that.

I have been sucessfull in retrofitting with a 70W T6 Lamp and a somewhat awkward reflector assembly. But it worked all be it dimmly. But at least I was able to test the LCD's and everything looks to be ok.

The lens is in fact a UV filter and I have found a suitable replacement (in fact about 200 of them have been sitting under my desk at work for over a year).

All that is left now is to put in a 250W HQI and properly design a reflector for it.

Thanks Again
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Old 4th December 2005, 12:00 PM   #5
diyAudio Member
Join Date: Dec 2005
Location: Paris
Default Blue filter replacement / philips LC441

As for the filter, if there is a greenish colour than it sounds like that is def a UV coating on it.
I have been given an LCD projector (Philips LC4441 with about 30 hours of usage only) that has a defective filter which makes the picture unwatchable (big area with yellowish to blueish wrong colours).
I have opened it and seen (from above) that the blue filter is distorted, maybe by heat (as opposed to the green and red filters which seem completely flat).
Does anyone know how to replace a filter on this model without damaging the light unit and where to find the filter ?
Thanks in advance.
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Old 4th December 2005, 08:10 PM   #6
diyAudio Member
Join Date: Jan 2003
Location: UK
marceljack, try this firm:

they will probably have the filter you require, if not they will either make you one or tell you where you can get hold of one or have one which will be very similar.

can you give any more details as to the size, thickness, or any pictures? Maybe we could help then. My guess it's it's just a band reflecting dichroic filter. Is it at 45 degrees to the light path so blue light is reflected by it at 45 degrees?

something like:

item numbers:


on the following page:

maybe, but without further details or maybe a picture or two it's impossible to help further.

Can you give us any more details?

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Old 4th December 2005, 09:05 PM   #7
diyAudio Member
Join Date: Dec 2005
Location: Paris
Default LC4441 filter

Thanks jrhilton for your prompt help.
The filter in question is not a reflective filter but a transmitting filter on the light path just in front of the blue LCD.

There are of course 3 LCDs forming 3 sides of a square seen from above (after having removed the main electronics board).
With the lens "north", the green LCD is at south, the red is east and the blue west.

The filter seems orange in colour.
My first problem is to find how to remove the distorted filter without damaging anything in the optical unit, since I don't have the service manual.

Thnaks again !
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Old 2nd October 2006, 03:54 AM   #8
diyAudio Member
Join Date: Oct 2006
Default trying to retrofit PT-L595U lamp

I have recently acquired a Panasonic PT-L595U LCD Projector with a blown lamp. The start of this thread was about retrofitting one of these projectors with a cheaper metal halide bulb and I would like to attempt to do this.

Could anyone help me out with attempting to trick the circuitry into thinking the correct bulb is there and working? I know it's possible, I just have to figure it out.

Also, there is a glass plate that seems to be shielding the light cavity from the rest of the projector that has a crack in it. Is this a polarizing plate, a UV shield, or just a heat shield? Will the crack have a large effect on the output of the projector?

Any help would be greatly appreciated.

Thank you in advance!
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Old 2nd October 2006, 04:41 PM   #9
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Join Date: Nov 2004
Location: london
pictures/more detail
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Old 3rd October 2006, 05:45 AM   #10
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Join Date: Oct 2006
Default Metal Halide Bulb

I have managed to figure out how to trick the electronics on my PT-L595U into thinking the original bulb is there and can get the LCD to come on. For the time being I'm not going to worry about the cracked glass plate, if it becomes an issue I'll be back with more questions.

Now I'm trying to find small metal halide bulbs (250W). All of the bulbs I have found are around 8 inches long. Are there any distributors that sell metal halide bulbs that are around 2 inches long?

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