How to tell if a lamp is bad? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 17 Old 10-15-07, 11:55 PM
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How to tell if a lamp is bad?

My basic question is: How can I really tell if a projector lamp is ready to be replaced? Does it simply burn out, like a normal light bulb, or are there other failure modes?

Here's the longer version:
I bought an H31 about 20 months ago. I used it for just a little while before putting it into the closet while I finished my basement. A few months ago I brought it back out. At the 60 hour point, I started getting intermittent problems, where the projector would sometimes not power up--I would get a flashing orange "lamp" led. This supposedly meant that the lamp was bad, but I was surprised to be getting the problem with so few hours on the projector. Further, when the projector would power on, I could use it for hours. I tested use for up to 6 consecutive hours, and it NEVER shut off after successfully turning on.

So, I contacted Optoma and they had me send in the PJ for repair. They replaced the main board and the lamp driver, but told me that I needed a new lamp, as mine was going bad. I asked them if the lamp failure wasn't due to the bad lamp driver (perhaps over or under-driving the lamp, or not supplying stable power) and they told me that somehow they had determined that the failure was not due to the driver. I find this highly suspicious. In my experience a bad or unregulated power supply (which is what I'm assuming the lamp driver is) very often leads to component failure.

Anyway, now I have the projector installed again and I am getting the same problem. The PJ will intermittently turn on, and when it does turn on I can use it for hours at a time. For some reason, removing and re-seating the lamp allows the PJ to work properly almost all of the time.

So, how can I tell if the lamp is really bad? I assume that once it's bad it will just not power up at all. Is that correct? I'd like to educate myself a bit more on how exactly the lamp fails, so I have firmer ground to stand on when I call again and ask for a lamp replacement.
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post #2 of 17 Old 10-16-07, 06:12 AM
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Re: How to tell if a lamp is bad?

The only way that is even close to practical to know a lamp is bad is to test it on a known good supply in a known good set. That is, unless it is physically broken.

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post #3 of 17 Old 10-16-07, 10:36 AM
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Re: How to tell if a lamp is bad?

I'm wondering this myself. We have been using a Sanyo Z4 as our daily watcher for over a year now. I think I am noticing the light output going down, but I'm just not sure. Sometimes it competes with ambient light, sometimes not.

I almost want to get a light-meter so I can baseline it and know for sure.

Also, I hear the stories of failures after 100 hours and some that get 10,000 out of a bulb.
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post #4 of 17 Old 10-16-07, 12:09 PM
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Re: How to tell if a lamp is bad?

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lcaillo wrote: View Post
The only way that is even close to practical to know a lamp is bad is to test it on a known good supply in a known good set. That is, unless it is physically broken.
Well, the system just came back from being repaired, and it passed their "quality assurance" testing. I suppose I could assume that my PJ is good now, but I don't really have any way of being sure.

Is it unreasonable to assume that a bad lamp driver would cause premature lamp failure? They told me that they had determined that the lamp failure was not due to the bad driver, but I'm unsure of how they could actually do that.
post #5 of 17 Old 10-16-07, 08:18 PM
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Re: How to tell if a lamp is bad?

I don't know how they could make that determination unless the lamp had reached the number of hours it was rated for.

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post #6 of 17 Old 10-16-07, 11:19 PM
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Re: How to tell if a lamp is bad?

I believe the bulb life actually should follow the half life curve, so when it is rated at 2000hrs it would in theory be half the light output.

These bulbs actually lack a little Red out of the block, and over time this effect appears to worsen. My bulb is at 1100 hours, I did a calibration on it last Saturday night and light output is a struggle, what I really noticed was how far Red was reduced in certain standard modes.
Visually I noticed faces heading a little green and or pink at times, so as the bulb ages I also think one needs to tickle the adjustments, colour/tint more often.

This aside, you I believe did the right thing to send it back. Here though what they did is weird, to change those components and not change the bulb aswell is weird if the problem still exists. Although they said, replace the bulb, so why not just do that in the process?
Although you dont mention warranty at all, so I presume you had to pay for the service, if so why again didnt they change the bulb? If it was a warranty job, it is a difficult position for the customer as you have to trust the service people.
What is and what isnt causal can lead to arguments, there I believe the right thing to do would be replace the bulb for customer satisfaction. Even if it wasnt casual, proof is hard to establish, where as satisfaction and return business is assured if the product is returned working.

At this point I would buy a bulb, if it fixes the issue, great, move on.
If the problem continues, return it to the service agent and take the value of the bulb off the bill. Since it was their statement that it would fix the problem.

Light changes what it is doing depending if we are looking or not. Considering we only see this as a reflection of the past....what is it really doing now?
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post #7 of 17 Old 10-19-07, 04:06 AM
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Re: How to tell if a lamp is bad?

I must have installed at least 25 optoma projectors this year. Most of them are home theater projectors.I had come across some problem in 3 projectors.

What i believe is the projector needs to be properly shut down. In India we face power failures , hence we use "UPS" ( uninterrupted power supply ). The projector lamp needs to cool down and that's why even when you switch off the projector with the remote, the fan keeps running even after switching off for 20-50 sec depending on the room temperature and the lamp heat . When ever you ceiling mount a projector make sure the air-conditioner is not too close. So that you don't cool the lamp and kick it on .

I prefer not to switch on the projector immediately after switching off , cause kicking on the lamp when it is too hot must be avoided.

Facts on lamp life:

Every manufacturer claims 2000/3000 hrs . The exact way to achieve is to avoid too many switch on's. Plan for a movie and switch on . If you are going to switch on and off a minimum 10 times a day ,Your lamp life might not even reach half its life.

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post #8 of 17 Old 04-12-11, 04:46 PM
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Re: How to tell if a lamp is bad?

We have two Toshiba TDP-45 projectors that are a couple years old. One bulb burnt out, and so we ordered a new one. After replacing the bulb, the projector fails to do anything. It has no power at all. Is it possible that the new bulb was damaged in shipping? Should putting the old bulb back in at least let the power lights come on?
So you might ask, what about the second projector. Well, we opened it up to test the bulbs, and opening that bottom door turned that projector into a lump of plastic and metal too.
At this point, I thought power supply, open door kill switch, heat switch, etc. So, now having two completely failing projectors and three useless bulbs, I opened one of them up. Using a Volt-OHM meter, and the patience of Job, I checked the heat switch, and the kill switch the best I could, and determined that the switch was working and 110V getting to the inside of the projectors. Tried jumpering the connections on the door switch to see if that was the problem. So far a good 40 hours of thinking and measuring for naught.
Best I can tell is that opening the bottom door, to change the bulb, completely fried two projectors. So, can I tell if it is 3 bad bulbs causing all of this, or determine a course of action in some way?
We have since purchased two new projectors, but this has become a mission.
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post #9 of 17 Old 04-12-11, 07:03 PM
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Re: How to tell if a lamp is bad?

Just my $0.02 worth.

My BenQ W5000 is my fourth projector since 2000. My last three were LCD. What I noticed with them was as the lamps aged, the image got yellowish around the edges. Lamp strike failures are usually due to the electronics that drive the display, not the lamp itself unless the lamp has either exceeded its life or being damaged. The lamps are high pressure vapor (mercury) and do not have a filament, so it is not like a sudden jolt can break that. Acid from your finger prints can damage the glass as it heats up and why you should not touch them with your fingers. Sometimes the socket that the lamp module plugs into can be loose and not make proper contact and the result will be a lamp strike failure.
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post #10 of 17 Old 05-23-11, 03:30 AM
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Re: How to tell if a lamp is bad?

When you notice picture quality fading then surely its the time for replacing.

If the lamp explodes in the unit and the cage is not designed to properly hold in the glass you can end up with jammed fans or broken color wheels/light pipes.
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