Ila ® Back Focus - Hughes JVC 220 Service Manual

Chapter 3 Service Adjustments
3.4 ILA ®
3-6
Back Focus
®
The ILA Back Focus adjustment moves the ILA
assemblies together to adjust the focal length. This adjustment
allows the zoom lens' tracking to remain focused throughout the
entire range. Use focus test pattern to perform this adjustment one
color at a time. This procedure performs the Green ILA
Focus.
For best results, perform ILA
person will watch the screen close-up and the other will move the
®
ILA /Relay Lens/CRT assemblies back and forth. The adjustment
is factory-set but may need some touch-up in the field.
®
To adjust the ILA Back Focus:
1. Remove the rear cover (Section 4.2).
2. Tilt up the Electronic Module (Section 3.3).
3. For this procedure, view Green. Hide Red and Blue.
4. Select the Focus test pattern.
5. Select Projection Lens from the menu.
6. Use the up/down arrow keys to zoom the Projection Lens to full
telephoto position (smallest image). NOTE: Skip this step when
using an optional fixed lens.
7. Use left and right arrows to focus the projection lens to get
sharply focused spacer balls. NOTE 1: Spacer balls are used
®
inside the ILA Assembly to separate the layers. They are tiny,
random, irregularly-shaped spots that are visible throughout the
image. Look directly in front of the screen in the lighter areas of
the image to view. From throw distances shorter than 4 meters,
spacer balls are difficult to see.
8. Zoom the lens to a wide angle position (largest image). NOTE:
Skip this step when using an optional fixed lens.
9. Put on safety gloves (see Safety section for gloves type) then
loosen the wing nut on the Green Relay Lens (or whichever
lens is being focused). NOTE: If the ILA
assembly cannot be moved close enough to get a good spacer
ball focus, loosen the CRT Lens Stopper Ring in front of the
CRT Holder Ring (Figure 3-5). Move the CRT snug against the
collar to get additional range, and then, retighten the collar.
10. Loosen the 2 hex bolts (Figure 4-12) on the ILA
front of the Relay Lens.
11. Slide the Relay Lens/CRT/ILA
until the sharpest spacer ball focus is achieved. NOTE: Do not
use the zoom lens focus while performing this step.
®
®
Back Focus with 2 people. One
®
/Relay Lens/CRT
®
assembly forward or backward
Model 220 Service Manual
/Relay Lens/CRT
®
Back
®
assembly in