HP 3478A Technical Manual page 71

7-1. INTRODUCTION 7-1. INTRODUCTION
7-2. This section of th 7-2. This section of the manual has infor e manual has information on how
to troubleshoot and repair the 3478A multimeter with the to troubleshoot and repair the 3478A multimeter with the
information given information given in in Service
troubleshooting procedures to select an appropriate troubleshooting procedures to select an appropriate
group are also given in Paragraph 7-27. group are also given in
recommended to use the procedures first, before going recommended to use the procedures first, before going
to a service group. to a service group. Section VI Section VII also
complete Theory of Operation (in Service Group F), the complete Theory of Operation (in Service Group F), the
complete schematics (in Service Group G), and the complete schematics (in Service Group G), and the
necessary safety necessary safety considerations. considerations.
separated as follows: separated as follows:
The 3478A 's Theory of Operation is in The 3478A 's Theory of Operation is in
Service Group F (next to the last group). Service Group F (next to the last group).
a. a. Safety Safety Considerations Considerations - - paragraph 7-3.
b. b. Recommended Recommended Test Equ
c. c. Miscellaneous Miscellaneous Information Information - - paragraph 7-10.
1. 1. Instrument Instrument Disassembly (PC Disassembly (PC Board
Replacement) - see Section V. Replacement) - see Section V.
2. 2. Fuse Fuse Replacement Replacement - paragraph 7-13.
d. d. Troubleshooting Troubleshooting - - paragraph 7-15.
1. 1. Introduction Introduction - - paragraph 7-16.
2. 2. 3478A 3478A Self-Test Self-Test - - paragraph 7-18.
3. 3. Service Gr Service Group Selection oup Selection - - paragraph 7-27.
7-3. SAFETY 7-3. SAFETY CONSIDERATIONS CONSIDERATIONS
7-4. 7-4. The 3478A The 3478A has been has been designed w
safety standards. safety standards. To maintain To
cautions, warnings, and other safety related information cautions, warnings, and other safety related information
in this manual must be followed when servicing the in this manual must be followed when servicing the
instrument. Servicing should instrument. Servicing should only b
service personnel. service personnel.
7-5. 7-5. Calibration, maintenance, Calibration, maintenance, or or repair
instrument with covers removed while any power or instrument with covers removed while any power or
voltage is applied, should be avoided as much as voltage is applied, should be avoided as much as
possible. possible. If any If any work is done wh work is done while power and/or
is applied, the work should be carried out by a skilled is applied, the work should be carried out by a skilled
person who is aware of the hazards involved. person who is aware of the hazards involved.
mation on how
Service Groups. Groups. Preliminary Preliminary
Paragraph 7-27.
I also has the has the 3478A's
The The section section is is
NOTE NOTE
paragraph 7-3.
Test Equipment ipment - paragraph 7-8. - paragraph 7-8.
paragraph 7-10.
Board
- paragraph 7-13.
paragraph 7-15.
paragraph 7-16.
paragraph 7-18.
paragraph 7-27.
designed with interna ith international
maintain these these standards, standards, the
only be done e done by qualified by qualified
repair of of the
ile power and/or voltage
SECTION VII SECTION VII
SERVICE SERVICE
Any interruptions of the protective grounding Any interruptions of the protective grounding
conductor (inside or outside the instrument) conductor (inside or outside the instrument)
or disconnections of the protective earth or disconnections of the protective earth
It is It is terminal terminal
dangerous. dangerous.
3478A's
protective grounding conductor is strictly protective grounding conductor is strictly
prohibited. prohibited.
7-6. 7-6. It is possible It is possible for capacitors insid
remain charged when the instrument has been turned off remain charged when the instrument has been turned off
or its power source disconnected. or its power source disconnected.
7-7. 7-7. Make sure Make sure that only
(fast blow, correct current rating, etc.) is used for (fast blow, correct current rating, etc.) is used for
replacement. replacement. The use
circuiting of fuse holders must be avoided. circuiting of fuse holders must be avoided.
The service information given in this manual The service information given in this manual
is normally used with the instrument's is normally used with the instrument's
protective covers removed and with power protective covers removed and with power
applied. Voltage applied.
may, if contacted, result in personal injury. may, if contacted, result in personal
7-8. RECOMMENDED 7-8. RECOMMENDED TEST
7-9. 7-9. The recommended test The recommended test equipment is listed
4-2 4-2 in Section IV of this manual. in Section IV of this manual.
7-10. MISCELLANEOUS 7-10. MISCELLANEOUS INFORMATION
7-11. Instrument 7-11.
ment) ment)
tional
the
7-12. To replace the 34 7-12. To replace the 3478A's main print
the instrument must the instrument must be complete
procedure to disassemble the instrument is in Section V procedure to disassemble the instrument is in Section V
(Replaceable Parts) of this manual. (Replaceable Parts) of this manual.
7-13. 7-13. Fuse Fuse Replacement
the
7-14. 7-14. The 3478A
power fuse and the other one is to protect the instrument power fuse and the other one is
voltage
in the DC and in the
replaced as follows: replaced as follows:
7-1 7-1
WARNING WARNING
can can make make
Intentional Intentional interruption
for capacitors inside the instrument
that only the recommended the recommended fuse type
The use of repaired of repaired fuses and t
WARNING WARNING
Voltage or signals or signals at man
TEST EQUIPMENT
equipment is listed in in Table
INFORMATION
Instrument Disassembly Disassembly (PC
78A's main printed circuit board,
be completely ly disassembled.
Replacement
The 3478A has two fuses, has two fuses, one fuse is th
DC and AC Current AC Current Functions. Functions. The fuses are
TM 11-6625-3071-14 TM 11-6625-3071-14
the the instrument instrument
interruption of of the the
e the instrument to to
fuse type
fuses and the short- he short-
at many points y points
injury.
EQUIPMENT
Table
(PC Board Board Replace- Replace-
ed circuit board,
disassembled. The The
one fuse is the main e main
to protect the instrument
The fuses are