Maintenance; Locations Of Dc Power Supply Fuses; Replacement Of Display Sensitivity Lamps - HP 3720A Service Manual

Section II
2-19 MAINTENANCE
6.
Remove the four nuts holding the A18/A19
housing assembly to the front panel. If
necessary, gently move the wiring to gain
access to the nuts.
Release screw B shown in Figure 2-1.
Holding the A18/A19 housing assembly with
one hand, gently press the Display Sensi-
tivity panel on the front of the instrument
with the other hand to release the assembly.
Replacement of the A1 8/A19 housing assem-
bly is a reversal of the above procedure.
CAUTION
When handling the 3720A do not tilt the
instrument onto its front panel.
7.
8.
9.
2-20 Locations of dc Power Supply Fuses
2-21 Access t o the +158V, +50V, +15V, +5V, -1 5V,
-22V and -5OV power supply fuses is gained by
removing the bottom cover of the instrument.
2-22 The +12.6V power supply fuse is on the A20
Storage assembly. Access to the fuse is gained by
removing the top cover of the 3720A.
2-23 Replacement of Display Sensitivity Lamps
2-24 The lamps are mounted on the A18 and A19
assemblies. To replace the lamps the A18/A19
housing assembly must be removed from the
instrument and then dismantled.
3
2-25 Removal of A18/A19 Housing Assembly
(
103720 x O O 5 6 j
1. Remove the top cover, left side cover and
fluted aluminium plate from the instrument.
Note that the fluted aluminium plate is self-
adhesive.
Figure 2-1 A18/A19 Housing assembly
retaining screws
2-26 Dismantling the A18/A19 Assembly
2.
1. Remove the A18/A19 housing assembly as
detailed i n Paragraph 2-25.
2. Release the two screws holding the range
units lamp separator in place.
3. Slide the separator away from the assembly.
Release the two screws securing the A l / A l l
retaining strip and lift this strip clear.
3.
4.
Remove assemblies A2 to A6 inclusive.
Release the two screws a t the base of the
left hand board guide and withdraw the
board guide.
CAUTION
If the separator is forced sideways the units
lamps will be damaged.
I
5. Remove the left hand board guide support
by releasing the three screws A shown in
Figure 2-1.
.3
2-3
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