JVC 340 SC - Manual (Page 109)

Chapter 3---Service Adjustments
Model 330, 340SC, 370SC Service Manual 3-19
4. When the hot spot is at the center of the screen, retighten the four (4) Arc
Lamp holding screws.
Figure 3-10 Model 330 Arc Lamp Adjustments (the Heat Sink has been
removed for photograph).
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.
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.
4. Retighten the set screw.
Z-Axis Adjustment
3 of 4 Arc Lamp
Holding Screws
(bottom screw
not shown)
X and Y
Adjustments
Z axis set screw