Maintenance 
REASSEMBLY PROCEDURE 
A 
6. 
FRONT 
PANEL 
DISPLAY WINDOW 
Figure 
6-8. 
Removing 
the 
Display 
Window 
7. 
Set  the  chassis right  side up. 
8. 
Insert the FRONTREAR switch  rod through the 
front  panel  and  snap it  into  place. 
9. 
Reinstall  the  CAL 
ENABLE 
switch push  rod  by 
inserting the cylindrical end of the push rod into the 
rear of the front panel, then snapping it onto the CAL 
ENABLE switch plunger. 
CAUTION 
Make  certain that  the  CAL  ENABLE 
switch  shaft  is  in  the  out  (disabled) 
position after  the  CAL  ENABLE  push 
rod 
is 
installed. 
If 
the 8840A is switched 
on with the CAL ENABLE switch in the 
enabled  position,  the 
8840A 
may 
require  recalibration. 
10. 
Position the slot in the lower edge of the Line Voltage 
Selection Switch PCA in  the slot  on  the  lower  rear 
panel  standoff. Secure the  top of  the  Line  Voltage 
Selection Switch 
PCA 
to the upper standoff using the 
single mounting screw, and plug the ribbon cable into 
the  Main  PCA. 
11. 
Connect  the  power  supply  ground  lead  to  the  rear 
panel mounting stud. (The stud is located near the rear 
panel  power  receptacle 
as 
shown  in  Figure 
6-6F.) 
WARNING 
TO AVOID ELECTRIC SHOCK, ENSURE 
THAT  THE  POWER  SUPPLY 
GROUNID 
LEAD 
IS FlRMLY  AlTACHED TO 
THE 
REAR  PANEL MOUNTING STUD. 
12. 
Attach the two mounting screws on either side of the 
rear  panel  power  receptacle. 
13. 
Connect the two ribbon cables to the Display PCA to 
the  connectors. Push  the  cables straight  in  to avoid 
damage. 
14. 
Reinstall the harness 
in 
the sidewall cable guide, and 
secure  the  harness  to  the  chassis  with  the  cable 
clamps. 
15. 
Comect 
the leads to the four front panel input termi- 
nals according to the  color codes marked on the rear 
side of  the  Display 
PCA. 
16. 
Connect the leads to the four rear panel input termi- 
nals  following  the  color  codes  as shown  in  Figure 
66B. 
17. 
(Option 
-05 
only) Install the IEEE-488 Interface PCA 
according  to  the  instructions in  Section 
8. 
18. 
(Option 
-09 
only)  Install  the  True 
RMS 
AC  PCA 
according  to the  instructions in  Section 
8. 
19. 
Slide the  case  and  rear  bezel  onto  the  chassis. 
20. 
Install the  two  rear  panel  mounting screws. 
21. 
Install the case grounding screw in the bottom of the 
case. 
WARNING 
TO AVOID ELECTRIC SHOCK, ENSURE 
THAT  THE  GROUNDING  SCREW 
IS 
FIRMLY  ATTACHED  TO  THE  CASE 
BOTTOM. 
6-34 
INTERNAL FUSE REPLACEMENT 
For  fire  protection,  use  exact  fuse 
replacements only. 
The 
8840A 
has an internal 
3A 600V 
slow-blow fuse 
(F301) 
in series with the 
2A 
input terminal. To replace 
this 
fuse, 
remove the case according to the disassem- 
bly instructions. The fuse is held in fuse clips on the 
Main 
PCA. 
Do 
not 
use makeshift fuses or short-circuit 
the fuse holder. 
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