478 
Assembly Replacement Procedures
RF Area
Replacement 
1. Inspect the chassis where the YTF Preselector mounts and remove the gap 
pad if present (see Figure 14-34, item (1)). The gap pad may remain 
attached to the faulty YTF Preselector.
2. Refer to Figure 14-34. Install the replacement gap pad (1) into the recess 
in the base of the replacement YTF Preselector (2) Refer to A12MP1 in 
Chapter 13, “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 14-34  Gap Pad Installation
3. Refer to Figure 14-33. 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 14-32. Replace the cables W7 and W8. Torque to 10 inch-pounds.
5. Replace the wire harness W22.
6. Refer to Figure 14-9. 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 and Reference Bracket  
replacement procedure.
9. Replace the instrument outer case. Refer to the Instrument Outer 
Casereplacement procedure.