Adjustments Model 8904A
Adjustment
1
OUTPUT
GAIN
AND
OFFSET
Description
Four adjustments are made to the A3
or
A10 Output Assemblies. If the instrument has only one Output
Assembly (A3), the adjustments are made only to
it.
If the instrument has Option
002
with
two
Output
Assemblies (A3 and
AlO),
adjustments are made to one or both assemblies. Accessing A3 will require
extra disassembly.
If
the instrument has Option
006
(balanced output), adjustments are made on the
A3 assembly with the balance transformer disconnected. The four adjustments are made
as
follows:
1.
The DAC range is calibrated at maximum ac output (10 Vpp).
2. The dc offset of the Audio Amplifier is adjusted for
0
Vdc.
3. The dc offset of the Floating Output Amplifier is adjusted for
0
Vdc.
4. The DAC range is again calibrated but at maximum dc output (10 Vdc).
Equipment
Digital Voltmeter
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HP
3478A
Procedure
Setup
1.
Remove the instrument’s bottom cover.
2.
If the instrument has Option 002 (a second output assembly) and Output
1
(the output from the
A3
Output Assembly)
is
to be adjusted, move the A10 Output Assembly out of the way. (Refer
to the disassembly procedure in Figure
5-4.)
3.
If
the instrument has Option
006
(balanced output), disconnect the coax cable from A3J400
(OUTPUT
HIGH)
at
the front edge of the A3 assembly. In the steps that follows, when a
reference is made to the
OUTPUTS
1
HIGH
connector, make the connection to A3J400 instead.
Maximum
AC
4.
Connect the Multifunction Synthesizer
OUTPUTS
1
HIGH
output for the A3 Output Assembly
5.
On
the Multifunction Synthesizer, press
SHIFT
PRESET.
After the instrument presets, key in
or
OUTPUTS
2
HIGH
for the A10 Output Assembly to the voltmeter input. Switch
LINE
to
ON.
For A3 Output Assembly For A10 Output Assembly
fl
(Channel
Config.)
fl
(Channel Config.)
NEXT NEXT NEXT
SHIFT
FLOAT
1
OFF
SHIFT
FLOAT
2
OFF
FREQ
1
kHz
FREQ
1
kHz
AMPTD
10
V
AMPTD
10
V
6.
Set the voltmeter to measure ac volts. Adjust A3R224 or A10R224 (DAC
LEVEL)
for a level
between
7.06
and
7.07
Vac. (Refer
to
the Component Locator, Figure
5-6.)
5-4
Adjustment
1
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