HP 3478A Technical Manual page 72

3 3 4 78A 478A
a. a. Main Power Fuse. Main Power Fuse. To replace
fuse, fuse, first first remove remove power power from the
flatblade screwdriver rotate the fuse terminal (at the rear flatblade screwdriver rotate the fuse terminal (at the rear
panel) counterclockwise. panel) count erclockwise. Remove the
with a replacement (refer to this manual's Section II or with a replacement (refer to this manual's Section II or
Table 5-3 for the cor Table 5-3 for the correct value). rect value). Reinstall the terminal.
b. b. Amps Fuse. Amps Fuse. The Amps The Amps Fuse is
the 3478A' the 3478A's A (Amps) t s A (Amps) terminal (on the
replace the fuse, first remove any cables connected to replace the fuse, first remove any cables connected to
the A terminal the A terminal and then t and then turn the inst
side slots on the A terminal to rotate the terminal side slots on the A terminal to rotate the terminal
counterclockwise. counterclockwise. The The terminal
protrude from th protrude from the front panel. e front panel. Remove the terminal and
fuse, and replace the fuse with a 3A at 250V fast blow fuse, and replace the fuse with a 3A at 250V fast blow
fuse (-hp- Part No. 2110-0003). fuse (-hp- Part No. 2110-0003). Return the terminal and
fuse to the front panel. fuse to the front panel.
7-15. TROUBLESHOOTING 7-15. TROUBLESHOOTING
CAUTION CAUTION
The The instrument instrument
Integrated Circuits which are susceptible Integrated Circuits which are susceptible
to failure due to f ailure due to stat to static discharge.
especially important that grounded tools especially important that grounded tools
and wrist straps be used when handling and wrist straps be used when handling
or troubleshooting these components. or troubleshooting these components.
7-16 . . Introduction 7-16 Introduction
7-17. 7-17. The following The follow ing paragraphs paragraphs and S
have troubleshooting information and procedures for the have troubleshooting information and procedures for the
-hp- -hp- Model Model 3478A 3478A
troubleshooting and repairing the 3478A, make sure the troubleshooting and repairing the 3478A, make sure the
failure is in the instrument rather than from any external failure is in the instrument rather than from any external
connections. connections. Also Also make make sure
calibrated. calibrated.
7-18. 3478A 7-18. 3478A Self-Test Self-Test
7-19. 7-19. The 3478A The 3478A Self-Test is Self-Test is designed t
that most of the instrument's internal logic circuitry is that most of the instrument's internal logic circuitry is
operational. The test is selected operational. The test is selected when the 3478A is fir
turned on or by pressing the blue Shift button and then turned on or by pressing the blue Shift button and then
the SGL/TRIG the SGL/TRIG (TEST/RESET) (TEST/RESET) button.
paragraphs have the Self-Test Failures and some paragraphs have the Self-Test Failures and some
troubleshooting information. troubleshooting information.
7-20. 7-20. U501 RA U501 RAM Falls M Falls (U.C. RA
shows that the Chassis Common shows that the Chassis Common CPU's (Main Controller
U501) RAM has failed its internal self U501) RAM has failed its internal self test.
normally caused by normally cau sed by a defective a defective U501.
U501 is the cause, go to Service Group D, paragraph 7- U501 is the cause, go to Service Group D, paragraph 7-
D-21, for further troubleshooting. D-21, for further troubleshooting.
To replace the main the main power
from the 3478A. 3478A.
Remove the fuse and fuse and reinstall
Reinstall the terminal.
Fuse is located insid located inside e
erminal (on the front panel). front panel). To
urn the instrument off. rument off. Use the
terminal and and fuse fuse will
Remove the terminal and
Return the terminal and
contains contains CMOS CMOS
ic discharge. It is It is
and Service ervice Groups
Digital Digital Multimeter. Multimeter.
sure the the instrument instrument is is
designed to make sur o make sure e
when the 3478A is first st
button. The following The
(U.C. RAM FA M FAIL). IL). This
CPU's (Main Controller
test. The failure is The failure is
U501. To make sure To make sure
7-21. 7-21.
power
indicates that the 3478A has failed its internal ROM self indicates that the 3478A has failed its internal ROM self
With a With a
test. The Control ROM test. The Control ROM (U502) is the
Go to Service Group D, paragraph 7-D-19, for further Go to Service Group D, paragraph 7-D-19, for further
reinstall
troubleshooting. troubleshooting.
7-22. 7-22. Calibration RAM
test fails, an attempt made to calibrate the RAM was test fails, an attempt made to calibrate the RAM was
unsuccessful. Go to Service unsuccessful.
To
(Calibration Ram Failure) to check the CMOS RAM. (Calibration Ram Failure) to check the CMOS RAM.
Use the
NOTE NOTE
will then then
The CAL ENABLE Switch on the front panel The CAL ENABLE Switch on the front panel
should not be in the CAL/ENABLE position should not be in the CAL/ENABLE position
under normal use. under norm
position to calibrate or troubleshoot the position to calibrate or troubleshoot the
instrument. instrument.
7-23. 7-23.
Calibrate the 3478A. Calibrate the 3478A.
7-24. 7-24.
shows that the Chassis Common Processor (Main shows that the Chassis Common Processor (Main
Controller, U501) is unable to communicate with the Controller, U501) is unable to communicate with the
Floating Common Processor (A/D Controller, U462). Go Floating Common Processor (A/D Controller, U462). Go
to Service Group D, paragraph 7-D-44 (Isolation Circuitry to Service Group D, paragraph 7-D-44 (Isolation Circuitry
Troubleshooting) for troubleshooting. Troubleshooting) for troubleshooting.
7-25. 7-25. A/D Slope
Converter is unable to do a proper conversion, this test Converter is unable to do a proper conversion, this test
fails. fails. Go to
Converter Troubleshooting) for Converter Troubleshooting) for troubleshooting.
Groups
7-26. 7-26. A/D Test A/D Test Fails (A:D
the A/D Converter has failed the A/D Conv
Before Before
Service Group D, paragraph 7-D-35 (A/D Converter Service Group D, paragraph 7-D-35 (A/D Converter
Troubleshooting) for troubleshooting. Troubleshooting) for troubleshooting.
7-27. Service 7-27. Service Group
Service Service
Group Group
A A
B B
following C C
D D
E E
F F
G G
This test test
7-28. 7-28.
Information, Theory of Operation, and Schematics for the Information, Theory of Operation, and Schematics for the
3478A. 3478A. Service Group
and Service Group and Serv
the groups have troubleshooting information. the groups have troubleshooting information.
7-2 7-2
Control ROM Control ROM Fails Fails (U.C. (U.C. ROM
(U502) is the most likely cause.
Calibration RAM Fails (CAL Fails (CAL RAM FA
Go to Service Group D, para Group D, paragraph 7-D-23
al use. It should It should only be in
Uncalibrated Instrument Uncalibrated Instrument (UNCALIBRATED).
A/D Link Fails A/D Link Fails (A:D (A:D LINK FA
A/D Slope Error (A Error (A:D SLOPE :D SLOPE ERR).
Go to Service Group Service Group D, paragrap D, paragraph 7-D-35
Fails (A:D TEST FAIL). TEST FAIL). This sho
erter has failed its internal self t its internal self test.
Group Selection Selection
Table 7-1. 3478A Service Table 7-1. 3478A Service Groups
Title Title
DC DC Volts Volts and and DC DC Current Current Troubleshooting
AC Volts AC Volts and and AC AC Current Current Troubleshooting
Ohms Ohms Troubleshooting Troubleshooting
A/D Converter and Logic Troubleshooting A/D Converter and Logic Troubleshooting
Power Power Supplies Supplies and and Reference
Theory of of Operation Theory Operation
Schematics Schematics
The Service The Se rvice Groups Groups have have the
Service Group F has F has the Theory
ice Group G has G has the Schematics. the Schematics. The rest of
TM 11-6625-3071-14 TM 11-6625-3071-14
ROM FAIL). FAIL). This This
most likely cause.
RAM FAIL). IL). If If this this
graph 7-D-23
only be in that that
(UNCALIBRATED).
LINK FAIL). IL). The The failure failure
ERR). If If the the A/D A/D
h 7-D-35 (A/D (A/D
troubleshooting.
This shows ws that that
est. Go to Go to
Groups
Troubleshooting
Troubleshooting
Reference Troubleshooting Troubleshooting
the Troubleshooting Troubleshooting
the Theory of Operation of Operation
The rest of