Planar WN-5040-720, User Manual

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6.1 Changing a Lamp
You can change the lamp from the front or the rear.
When should I change the lamp?
Change the lamp when it fails. Lamp life is the
median life of a large sample of lamps. Median means
middle . It is not what most people think of as aver-
age .
Suppose the specification for lamp life is 5000
hours. If you had a large group of these lamps, more
than 100, and you turned them all on at the same
time, after 5000 hours
at least half of them would
still be on.
Suppose 50 of these lamps had failed after only 1
hours of use. Then suppose the rest of the lamps
failed after 5001 hours. The
average life of these
lamps would be 2501 hours.
But the median life specification is still valid,
because at least half of them lasted 5000 hours. This
is the way all lamp manufacturers specify lamp life—
as the median, not the average.
Taking a different case, suppose the first 50 lamps
failed at 1 hour and the rest of them lasted 10,000
hours. The specification is still valid, because
at least
half of the lamps were still working after 5000 hours.
You can’t tell from the lamp life specification how
long any one lamp will live.
Margay lamp life
The median lamp life for the Margay lamp is 6000
hours. If you routinely change the lamp at 6000
hours, you may be throwing away thousands of hours
of useful life. And you may be replacing it with a
lamp that is destined to last less than 1000 hours.
How to change the lamp from the front
1. Open the screen. (See 2.6.2 “Opening or Remov-
ing a Screen” on page 34.)
2. Open the door covering the electronics module
(on the right).
3. Turn off the AC power switch and remove the
power cord
4. Loosen the screw on the light shield.
5. Lift the cover and latch it.