Keysight Technologies N5261A, User'S And Service Manual

Page: 73 / 99

Service Information
Troubleshooting, RF Level
RF Out Failures
If the test ports are not switching, or fail the Operational Check the following
procedures can be used to verify the failure. The procedures assume power
supplies, controller board and front panel LEDs are working. Suspect the
switch Interface board, ribbon cable connection or RF switch. Refer to Table
2-1
on page
6 6
and Figure 2-1
3
on page
6 6
.
1. Inspect the ribbon cable connections from the RF switches to the Switch
Interface board (N5261-60001). Ensure the RF jumpers (E8356-20072) are
installed on SRC1 IN/OUT and SRC2 IN/OUT on the rear panel.
2. Start by measuring the power at SRC1 or SRC2, continuing through the RF
Amp, Directional Coupler
,
and Solid State Switch. If you find incorrect
power levels and suspect a component has failed , verify the DC voltages
referencing Table
2-1
on page
6 6
and Figure 2-1
3
on page
6 6
. Replace the
failed component.
If you suspect the RF Amp (5086-7771) substitute the LO Amp
(5086-7771) to verify the failure. The RF Amp uses a leveling circuit with
directional coupler and detector that also can be checked before replacing
the RF Amp. You may also substitute the Directional Coupler and Detector
from the LO Amp section. If the RF Amp is replaced
,
a gain calibration must be
pe r formed.
3. If you suspect the Solid State Switch (SW1 & SW2)
,
confirm that one of its
two LEDs toggle on/off when you send a Test Set I/O command. Refer to
“Measure RF OUT (Gain and Power)” on page
73
and Table
2- 3
on page
7 6
.
4. Substitute a known good switch, or connect a known good wire-harness
cable and retest. Replace if necessary.
5. If the problem is not the switch
,
measure the switch drive voltage on the
Interface board (J60 or J61, Pin 1) for a change in voltage ( − 10 V or +13.0 V),
use I/O command in Table
2- 3
on page
7 6
. Replace the Interface board.
LO Out Failure
If the LO Out fails the Operation Verification test the following procedure can
be used to verify the failure. The procedures assume power supplies,
controller board
,
and front panel LEDs are working. Suspect the switch
Interface board, Bias cable, RF pre-amp
,
or Power Divider.
1. If one or more of the LO ports are working, suspect the Power Divider.
2. If none of the port s are working, start by measuring the power at LO IN,
continuing through the pre-amplifier, LO Amp, Directional Coupler
,
and
Power Divider. If you find incorrect power levels and suspect a component
has failed
,
verify the DC voltages referencing Table
2-1
on page
6 6
and
Figure 2-1 3 on page 6 6 . Replace the failed component.
Keysight N5261/62A User’s & Service Guide
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