Infocus projector

I have a replacement lamp for an infocus projector. I would like to
check it to see if it is good. I used an ohmmeter to check across the
terminals but it registers open. I actually think that this is an a/c
bulb of some sort. I was wondering if I could just put 115v across the
terminals to check it. The bulb looks brand new and is supposed to be
good. I don't know the voltage rating of the bulb, but I'm sure it has
to be A/C. The bulb is 200 watts output. Is it possible for the bulb
to be some kind of funky gas discharge bulb that would show open with
an ohmmeter when the bulb is good?

thanks,
Tracy

 

You can't check it easily.

It's a high intensity discharge lamp and requires something like
30 kV to initiate the arc.

Even if you pull the back off your projection TV and apply its 30 kV
across the lamp and it flashes, still doesn't mean it's good.

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Yes, they usually are.

They need special control gear to make them work. Probably the only way
to test it is to fit it to the projector and see if it works.

 

You cant check with an OHM meter. Like everyone has said you have to put it
in the projector. If it is a new replacement lamp it shold be good. Some
lamps have fuses on the housing assembly. Check that. What model it the
projector? (infocus sucks anyways) Make sure the projector hasn't exceeded
tha lamp life. It may be in internal shutdown which requires you to reset
the lamp timer.

 

If this projector is the one that looks like a big clamshell, and was also
distributed by Electrohome in Canada, the following below would apply.

I was working for a place that had one of these projectors, among a number
of different types, for doing special shows. I used to do some of the
service on this projector type. If I remember correctly, this is a Xenon gas
discharge lamp. It used a very high current type high voltage, high
frequency pulse supply. It was in the order of about 5,000 Volts. You cannot
test this type of lamp without running it in the proper supply, proper
safety enclosure, and proper high pressure cooling. Its rated life span was
about 900 hours, but we have never seen one go for more than about 250
hours.

When firing up the lamp, there cannot be any finger prints, any dust, or
dirt on it, or the lamp will crack when operated. Finger prints must be
cleaned off with pure alcohol only.

This lamp is very high on medium to short-wave (UVB-UVC) UV output, and when
operated, the projector has some UV filtering incorporated in to the optical
elements that the light passes though. This is essential for this type of
lamp to meet safety regulations for viewing projected pictures that use this
type of lamp as the light source. Invisible reflected UV rays are also very
dangerous to the eyes.

--

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I have a replacement lamp for an infocus projector. I would like to
check it to see if it is good. I used an ohmmeter to check across the
terminals but it registers open. I actually think that this is an a/c
bulb of some sort. I was wondering if I could just put 115v across the
terminals to check it. The bulb looks brand new and is supposed to be
good. I don't know the voltage rating of the bulb, but I'm sure it has
to be A/C. The bulb is 200 watts output. Is it possible for the bulb
to be some kind of funky gas discharge bulb that would show open with
an ohmmeter when the bulb is good?

thanks,
Tracy

 

Isn't there also a concern that as the lamp ages, the pressure inside goes up
or the envelope becomes more brittle or something.

Lamp life is not only limited by electrical considerations but also by the
explosion hazard. I don't know if there's a way to determine if a lamp
is safe to use other than by number of hours it has been in use.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the Feedback Form at repairfaq.org. Thanks.

 

the chance of a violent explosion increases sharply near end of life.
hence the timer.

 

What would make the pressure go up?

Don't high temps usually anneal glass, making it less likely to break?
Is this also true for quartz?

-

 

these are under very high pressure cold.
this increases as it heats up.i bet the metal sputtered off the electrodes
blackens the arc tube and makes it run too hot.
this makes the pressure go up.