Agilent Technologies 35670A Service Manual page 229

Agilent 35670A
Step 2. Check the dc offset DAC.
G
• Using the BNC-to-SMB cable, connect the oscilloscope to A1 P200 to check
channel 1 or to A1 P700 to check channel 2.
If you changed the input signal or range, set the input signal to 2 Vp-p and the
range to 1 Vpk.
• Set the oscilloscope to 700 mV/div.
• Press the following keys:
[
System Utility
[ ]
MORE
[
SERVICE TESTS
[
SPCL TEST MODES
[
MORE SPCL MODES
[
CHANNEL 1 SPCL MODE
[
OFFSET DAC
0
[ ]
ENTER
• Note the dc offset voltage of the sine wave displayed on the oscilloscope.
• Enter numbers between 127 and +128.
The sine wave dc offset voltage should change about 780 mV for a −127 entry and
−780 mV for a +127 entry.
• If the dc offset function is incorrect, the A1 Input assembly is probably
faulty.
• If the dc offset function is correct, the A5 Analog assembly is probably
faulty.
]
]
]
]
] or [
CHANNEL 2 SPCL MODE
]
Troubleshooting the Analyzer
To troubleshoot input and ADC failures
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