408 Keysight NFA Series Noise Figure Analyzers Service Guide
Assembly Replacement Procedures
RF Area (N8973B, 74B, 75B)
Replacement
1. Inspect the chassis where the YTF Preselector mounts and remove the gap
pad if present (see Figure 15-14, item (1)). The gap pad may remain
attached to the faulty YTF Preselector.
2. Refer to Figure 15-14. Install the replacement gap pad (1) into the recess
in the base of the replacement YTF Preselector (2) Refer to A12MP1 in
Chapter 14, “Replaceable Parts.” for the gap pad part number. Peel back
one corner of the clear plastic backing on the pink side of the gap pad.
Remove the blue backing from the other side of the gap pad. Install the
gap pad as shown with the pink side exposed. Carefully peel off the clear
plastic backing and smooth the gap pad into the recess.
Figure 15-14 Gap Pad Installation
3. Refer to Figure 15-13. Place the YTF Preselector into the chassis with the
connectors toward the front of the instrument. Replace the four screws
(2). Torque to 9 inch-pounds.
4. Figure 15-12. Replace the cables W7 and W8. Torque to 10 inch-pounds.
5. Replace the wire harness W22.
6. Refer to Figure 15-8. Position the chassis side, right onto the chassis and
replace the thirteen screws. Torque to 9 inch-pounds.
7. Replace the front panel. Refer to the “Front Frame Assembly” replacement
procedure.
8. Replace the top brace. Refer to the “Top Brace” replacement procedure.
9. Replace the instrument outer case. Refer to the “Instrument Outer Case”
replacement procedure.
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