Local Oscillator Feedthrough Adjustment; Electrical Isolation Test - HP 3585A Service Manual

Adjustments
REF -2 1 . 7 dBm
1 RANGE -5. 0 dBm
dB/D I V
- - - -
- - - - - - - - - - - - - -
START 1 00. 0 Hz
RBW 3 KHz VBW
C 1 8 Correctly Adjusted
5·44. Local Oscillator Feedthrough Adjustment
a. Enter:
b . Adjust A I R 1 70 for a minimum marker reading (minimum LO feedthrough). Verify
that the marker reads
5·45. Electrical Isolation Test
a. Turn the 3585A power off.
b. Carefully replace the Input/Conversion Section in the 3585A mainframe. Replace and
tighten the seven mounting screws.
c. Connect all the coaxial cables to the Input/Conversion Section.
d. Before connecting the power supply cable, connect an ohmmett(r between the 3585A
frame and the screw closest to A I R 1 08.
e. The ohmmeter should read infinite resistance. This indicates that the Input/Conver­
sion Section is properly isolated from dc ground loops. If the ohmmeter shows a shorted
condition, check the capacitors on A6a,b,c or d.
f. Remove the ohmmeter.
g. Connect the power supply cable to the Input/Conversion Section.
h. Turn the 3585A power on.
5-68
MARKER 500 050. 0 Hz
-25. 42 dBm
:
t
- - - - - - - - - -
- - - -
STOP 1 000 000. 0 H z
10 KHz ST . 4 SEC
Figure 5·44. 1 MO Input Capacitance Display
INSTRUMENT PRESET
RANGE . . . . ' " . . . . . . . . . . . . . . . . . . . . . . . . . ' " OdBm
MANUAL ENTRy . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
::5
- 1 5dBm.
REF - 2 1 . 7 dBm MARKER 500 050. 0 Hz
1 dB/D I V RANGE -5. 0 dBm
START 1 00. 0 Hz
RBW 3 KHz VBW 10 KHz
C 1 8 I mproperly Adjusted
Model 3585A
-24. 82 dBm
STOP 1 000 000. 0 Hz
ST . 4 SEC