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Chapter 3---Service Adjustments
Model 330, 340SC, 370SC Service Manual 3-21
Figure 3-9. Model 340SC and 370SC Arc Lamp Adjustments
3. Verify that the condensing (collimating) lens assembly has not moved (see
Figure 4-1 or 4-2 and Photo 4-4). Check to see if the assembly is loose. It
should be unmovable in any direction.
4. The barrel of the lens assembly should be no more than 1½ inches (usually
much closer) from the blue dichroic mirror. If it needs to be moved closer,
first loosen the 3mm set screw located at the top of the mounting ring
(Photo 4-4) that the barrel sets in, then move the lens closer to the blue
dichroic mirror. This will increase the center brightness. Roll-off may not
be acceptable if the barrel is moved too far forward.
NOTE:
Be careful to maintain proper roll-off in these illumination optics
(arc lamp and condensing lens) adjustments. It is possible to get very high
brightness values at the screen center at the expense of proper roll-off. Try
to keep the ratio between center brightness and edge brightness. Roll-off is
2:1 to the edge and 4:1 to the corners (e.g.: if the center brightness is 20
foot-candles, the edge brightness should be at least 10 foot-candles and
preferably 10 foot-candles).
CAUTION!
Do not leave the roll-off at a value higher
than 4:1, or the center may be too bright and could result in
damage to the cold mirror.
5. Retighten the set screw.
3.12 Arc Lamp Current Adjustment
The Arc Lamp current must be reset whenever an Arc Lamp is replaced and
should be rechecked every 500 hours of Arc Lamp operation.
CAUTION!
If the Arc Lamp current is being adjusted due to
the installation of a new Arc Lamp or Arc Lamp/Ignitor assembly, the
current adjust pot (Photo 4-3) must be turned to minimum (fully CCW).
Failure to do this may result in damage to the equipment including failure
of the Arc Lamp, Ignitor, or power supply.
To check and adjust the Arc Lamp current:
1. Measure the output voltage at the System Power Supply (SPS) Ignitor
terminals J503 and J504. Note this figure.