R&S SM300  Instrument Assembly for Board and Module Exchange 
Version 04  43   
Service Manual SM300: 1147.1652.00               Instrument Part No SM300: 1147.1498.03 
1.3.3.9  Aircase Unit with Display and Fan 
Removing aircase 
unit
1. Remove both protectors (see section 1.3.3.1).
2. Remove handle (see section 
1.3.3.2).
3. Remove rear frame and both cases (see section 
1.3.3.3). 
4. Remove carrier lid (see section 
1.3.3.5).
5. Remove front unit (see section 
1.3.3.7).
6. Remove duoblind (see section 
1.3.3.8).
7. Remove generator module (see section 
1.3.3.11).
8. Undo  5  special  screws on  side  (see 
Figure 1-22)  and  lower  2  special 
screws (see 
Figure 1-23). 
9. Undo  2  countersunk  screws  (see 
Figure  1-24)  located  below  the 
backplane. 
10. Route spinwheel and keyboard cables through opening and disconnect 
from  backplane.  Disconnect  display  cable  and  fan  cable  latch  from 
backplane.  
11. Pull aircase unit off toward front (see 
Figure 1-25). 
Caution
Make  sure  the  color  marking  of  spinwheel  cable  is  at  top  and  the  color 
marking of keyboard cable points towards the display plug! 
Installing aircase 
unit
1. Mount aircase unit on instrument from front. 
2. Connect display cable and fan cable latch to backplane. 
3. Route  spinwheel  and  keyboard  cables  through  opening  and  plug  into 
backplane. 
4. Press aircase unit onto carrier unit and fasten it in place with 5 special 
screws  on  side  and  2  special  screws  at  bottom  (similar  to 
DIN 7985 M3×5). 
5. Fasten  two  countersunk  screws  located  below  backplane  (DIN 96  
M2.5×6).
6. Install generator module (see section 
1.3.3.11).
7. Install duoblind (see section 
1.3.3.8).
8. Install front unit (see section 
1.3.3.7).
9. Install carrier lid (see section 
1.3.3.5).
10. Install both cases and rear frame (see section 
1.3.3.3).
11. Install handle (see section 
1.3.3.2).
12. Install both protectors (see section 
1.3.3.1).
Figure 1-22  Figure 1-23