HP 3476A Operating And Service Manual page 27

Model 3476A Section V
WARNING
These servicing instructions are for use by qualified personnel only. To
avoid electrical shock, do not perform any servicing other than that
contained in the operating instructions unless you are qualified to do
so.
Wear clean cotton gloves when working on the main assembly circuit
board or switches. Contamination or fingerprints on high impedance
points on the main assembly will degrade the performance of the
instrument. Nylon gloves should not be worn due to the possibility of
static charge buildup.
The hybrid circuits in the 3476A may be permanently damaged by
static discharge from a hand or tool when the 3476A is disassembled.
The procedures below must be followed to prevent possible damage.
1. Ground the hand while disassembling and working on the 34764.
Conductive wristbands (-hp- Part No. 00970-67900) are available for
this purpose.
2. Attach the 3476A com terminal to earth ground. Touch all tools
to earth ground to remove static charges before using them on the
34764.
3. Use a soldering iron with a grounded tip.
PRE- ADJUSTMENT PROCEDURES.
A. Disassembly Instructions.
1. Remove the Multimeter Power Cord.
2. With the Multimeter in the inverted position, remove
the two screws in the bottom cover.
3. Remove the bottom cover.
4. Remove the internal shield.
5. Remove the Input panel and Input fuses.
6. Connect a jumper across the Amps input protection
fuse holder and across the Ohms input protection fuse
holder.
B. Turn- On Instructions.
1. Connect the Multimeter TP
,
s5
,
to earth ground.
2. An external 20 V dc power supply can be used to
provide instrument power. Connect the power supply
across C15 (500 microfarad 50 V dc electrolytic). Connect
positive power supply lead to the (+) end of C15 and the
negative power supply lead to the other end.
3. If external power supply is not available, use the ac
power cord and the appropriate ac line voltage as specified
by the option decal attached to the instrument.
5-5