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Old 7th March 2004, 07:51 PM   #1
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Default DIY replacement lamp for projector

Hi, I just bought a Ampro LCD-150 projector off ebay for really cheap. The only problem is it's bulb is out. I was thinking I could manage to set up a metal halide bulb instead. The problem i have is that it won't dispaly anything probably if there's a burnt out lamp, since the "Lamp" lcd is lit up. I was wondering if anyone had an idea to fool the thing into thinking the lamp works, so I can use it. I thought that maybe I could just close the circuit, and reduce the current to that used by the buld. Anyone wanna give me some advice here?
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Old 7th March 2004, 08:27 PM   #2
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Some projectors have a reset button for the lamp.
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Old 8th March 2004, 12:24 AM   #3
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If you're talking about the saftey switch that won't let it run if the cover's not on, I keep the switch pressed, but no luck. Do you guys think that the LCDs will still display without the light being on? if so, i have nothing to worry about
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Old 8th March 2004, 03:01 AM   #4
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And the unit uses a 250w MH light, so maybe I could use a regular 250w MH, but not one for projectors, and make a custom reflector and stuff, but still have it wired where the bulb is. Any thoughts?
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Old 10th March 2004, 01:31 PM   #5
Tuga is offline Tuga  United Kingdom
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Hi,

I have been reading this forum for a while now, but never had the time to build anything. Although I bought the Fujinon lens and a small lcd etc to try and build a basic projector, it never happened.

Anyway, I have bought a Projector with no bulb either.
It took a while to fool it but it’s done now.

before we start..
DO NOT PUT YOUR DVM ACROSS THE IGNITOR OUTPUT.
altough it created a nice blue arc between the meter probes...lol


You need to look for a few things:

Safety Switches:
it won’t power up if any of the covers is open.

Fans:
they might have rev control, if the projector knows they are not working it might not power up to prevent overheating or fire.

Temp sensors:
Self-explanatory.

Lamp:
Mine (Mitsubishi S120) had the lamp led flashing red.( over 1900hours gone)
After looking on the manual all I had to do was press 2 keys to reset it.

And of course, the current sensing.:
This is the tricky bit!

First I fitted a small 150W halogen bulb in the lamp compartment with the hope it would only have optical sensors…L nope!!!
So I had then to take every screw and part of the projector to open the power supply.
It’s common to use Opto Isolators or Opto couplers for current sensing on power supplies.

http://uk.farnell.com/jsp/catalog/vi...prodId=3565683

So look for these components. There will be at least 4 of them but the ones you want will be on the low voltage DC part of the PSU close to the igniters.
You should have one going active when U press “power” and the other should reply to the board once the lamp fires.
Look for 3 wires going to the psu from the main board, maybe.

All I had to do was to pull one line low and that was it…J.
The ballast, the igniter, and low DC part of the PSU ( made of 2 PCBs) aren’t even in the projector anymore.

I am sorry if it sounds complicated but English is not my native language.

I now have it working with a 15v 150W halogen bulb image is only visible with the room lights off but its ok, maybe a bit on the green side.

Hope this helps….





Any one knows how to build a 24v @ 10-15A PSU??
Or where to buy a cheap one?
Or maybe an easy and cheap way to power a 250w halogen bulb?
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Old 10th March 2004, 02:44 PM   #6
Tuga is offline Tuga  United Kingdom
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I know it ‘s obvious but I better say it any way.

DO NOT connect an Halogen bulb to your projectors PSU. The Halogen bulb must powered from an exteranal power supply.

DO NOT work on the PSU with it connected to mains.

DO NOT disable any of the safety features (switches, sensors etc) built in your projector.

DO NOT TOUCH any of the mains part of the PSU even after powered off. Capacitors can still give you a violent discharge.

DO NOT try to measure the striking voltage…lol
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Old 10th March 2004, 09:33 PM   #7
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Tuga: you said "All I had to do was to pull one line low and that was it"

I'm not sure what you mean here. Do you mean that all that you had to do was disconnect one cable? If I post a few pictures of my circuits, can you give me some advice? I think I've narrowed the Opto things to only a few possible ones, and you might be able to tell me which one I need to concentrate on.
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Old 10th March 2004, 10:04 PM   #8
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And will it work to just throw a 250 watt MH in, and forget all the bypassing stuff... since the original lamp is a 250 MH projector lamp, is the circuit compatable with that of a regular one?
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Old 10th March 2004, 10:18 PM   #9
Tuga is offline Tuga  United Kingdom
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Hi,

I mean there was a line that was high (+5v) until the Opto pulls it low (0V).
I have removed part of the circuit that had the optos so I connected that line to 0V permanently.

You said u narrowed it down. Take the numbers on those components and make a search on Google. If it mentions opto isolators or opto decouplers you know they are the ones.

You will need basic knowledge of electronics to figure out the circuit around them, so you know to which pin should you attach what voltage.
You will need a multimeter (DVM) as well.

Take all the safety measures.
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Old 10th March 2004, 10:24 PM   #10
Tuga is offline Tuga  United Kingdom
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About the “just throw a 250 watt MH in, and forget all the bypassing stuff” I have no idea.
That was going to be my next step if I couldn’t find a way to bypass it.
Now that I have a working projector I don’t feel like blowing it to bits.
I you decide to try this option remember that you are dealing with over 5000Volt pulse to ignite the lamp. You might want to try it with the lamp outside your projector….and take cover….lol.

But it might just work.

Keep me posted.
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