HP 3465B - Power Supply Adjustment; Input Amplifier Adjustments

Model 3465B ADJUSTMENT PROCEDURES
Section V
d. Remove top shell and disconnect power supply cable
(red/black).
e. Disconnect the A2 pc assembly from the A1 pc
assembly and fold over the front panel. Do not disconnect
the ribbon cable.
f. Remove four spacers.
g. Remove one screw in the center of the A1 pc assem
bly.
h. Reconnect the A2 pc assembly to the A1 pc assem
bly.
i. Invert the Multimeter so that it rests on the front
panel and the A2 pc assembly.
j. Remove the bottom shell.
k. Reconnect the Power Supply cable and the ac power.
NOTE
After use of a soldering iron, flux remover or
freon on the A1 Assembly, allow 10 to 15 min
utes for the instrument to thermally stabalize
before an adjustment is performed. If cleaning
solvents or flux removers are used, they must
be residue-free or be rinsed away. Residues on
the instrument surfaces may cause instabilities
or inaccuracies.
5-30. Power Supply Adjustment.
5 31. Power Supply + 10 V Reference Voltage Adjustment.
Coarse adjustment of the -f 10 V reference voltage is made
by selecting the proper combination of power supply jump
ers designated 1, 2, 4, 8 and 16. Coarse adjustment is neces
sary whenever the -f 10 V reference cannot be adjusted with
A1R89 and Jumper JR(+ 10 V ADJ - fine adjustment) to
obtain a display of 1.0000 for a 1 V dc input. This can
occur after replacement of A1CR17, A1R75 or A1U16 or
because of the long-term drift of the A ICR 17 zener
voltage.
5-32. Power supply jumpers 1, 2, 4, 8 and 16 parallel
resistors in A1R75 which are used as a regulator feedback
network. Removing a jumper decreases the -f 10 V refer
ence voltage and results in an increase in the Multimeter
display for a given input.
5-33. A DC Standard is required for this adjustment.
a. Set Multimeter function to DCV ( V) and range
to2 V.
c. Apply + 1 V dc from the DC Standard between the
VS2 and COM terminals.
d. Note and record the Multimeter display.
e. Refer to Table 5-9, Power Supply Jumpers. Locate
the line with LO and HI reading limits that bound the
Multimeter display recorded and note the jumper combina
tion. (If reading is out of range of table, check A1CR17 for
6.95 V ± 0.25 V, A1R75 and A1U16).
f. A "0" means to remove jumper; a "1" means leave
jumper in place. Introduce the jumper combination noted
in Step e.
g. Remove the connection from R75 pin 22 to ground.
h. Adjust A1R89 (+ 10 V ADJ) for a Multimeter
display of + 1.0000 ± 2 counts. If the adjustment range of
A1R89 is insufficient, remove jumper JR.
NOTE
If a display of + 1.0000 cannot be attained with
AIR89 after installing the proper jumper com
bination, a new jumper combination must be
selected. If the + 1.0000 display is low, install
the jumper combination from the line in Table
5-8 preceeding the jumper combination
installed. If the + 1.0000 display is high, install
the jumper combination from the line in Table
5-8 succeeding the jumper combination
installed.
5-34. Input Amplifier Adjustments.
5-35. Input Amplifier Gain Adjustment (R76). A DC
Standard is required for this adjustment.
a. Set the Multimeter function to DCV ( V) and
range to 20 m.
b. Connect a short across the input terminals (VS2 and
COM) and adjust the Multimeter display for 0.000 with
R25 (rear panel ZERO ADJ).
c. Remove the short from the input terminals and apply
■f 10 mV to the input terminals from the DC Standard.
d. Adjust R76 (INPUT AMP GAIN ADJ) for a Multi
meter display of -I-10.000 ± 3 counts.
5-36. Input Amplifier Balance Adjustment (R50/R51 po
tentiometer). The input amplifier balance adjustment must
be performed if A1Q16, AlUl or A1R75 are replaced. A
voltmeter is required for this adjustment.
b. Coimect A1R75 pin 22 to ground.
a. Set Multimeter function to DCV ( V) and range
to 2 V.
5-9