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Corrective Maintenance
1780R-Series Service Manual
6–7
Use the following procedure to replace the graticule lights.
1. Remove the SCALE, FOCUS, INTENSITY, VERT POS, and HORIZ POS
knobs by loosening their set screws.
2. Use pliers to grip the CRT Panel protrusion where the SCALE control shaft
is located. Carefully pull the panel outward until it pops out. (This panel is a
strip measuring 1-1/16-inch wide and 12-1/4 inches long. It is located below
the CRTs; see Figure 6–1.)
3. For graticule lights outside of the plastic light guide: Put some masking tape
on the inside surface of the long-nose plier jaws. Use the pliers to gently
grasp the bulb without crushing it; pull the bulb straight out of its socket.
Plug the new bulb into the socket.
4. After replacing the bulb, install the parts that were removed.
NOTE. For graticule lights located behind the plastic light guide, continue with
Step 5 and on.
5. Remove the three screws that hold the plastic CRT Frame Outer Bezel to the
chassis. These screws are located below the CRTs. See Figure 6–1.
6. Gently pull outward on the bottom edge of the CRT Frame Outer Bezel. Be
careful that the wire to the PROBE BNC connector stays connected. (The
top edge of the outer bezel will remain attached because it has three curved
protrusions or tabs that serve as a hinge.)
NOTE. If the CRT Frame Outer Bezel is swung out too far, the wire for the
PROBE BNC connector may pull out of the connector. If this occurs, the
instrument has to be removed from the rack mounting cabinet or portable case to
obtain access to the wire. Then, the wire can be pushed back into its original
position.
7. Remove the light guide that covers the defective light bulb. Use long-nose
pliers to replace the plug-in bulb as described in step 3.
8. After replacing the graticule light, reverse the removal procedure to reinstall
all the parts.
Graticule Light Removal