JVC 330 Service Manual page 109

4. When the hot spot is at the center of the screen, retighten the four (4) Arc
Lamp holding screws.
X and Y
Adjustments
3 of 4 Arc Lamp
Holding Screws
(bottom screw
not shown)
Figure 3-10 Model 330 Arc Lamp Adjustments (the Heat Sink has been
To refocus the Model 330 Arc Lamp:
1. Loosen the Set Screw on the Arc Lamp shaft.
2. Adjust the Z-axis hexhead screw so that the screen is fairly even in
brightness from center to the corners with the center being the brightest.
3. Use a light meter and adjust the Z-axis adjustment screw for a roll-off
(drop in brightness from center to corners) of a maximum of 4:1
(preferably closer to 2:1).
Example: If the center of the screen measures 20 foot-candles, the
corners should measure 10 foot-candles ideally,
but no less than 5 foot-candles.
than 4:1, or the center may be too bright and could result in
damage to the cold mirror.
4. Retighten the set screw.
Model 330, 340SC, 370SC Service Manual
removed for photograph).
CAUTION!
Do not leave the roll-off at a value higher
Chapter 3---Service Adjustments
Z axis set screw
Z-Axis Adjustment
3-19