154 Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide
Troubleshooting
Pulse Modulation Issues (Option UNW)
Pulse Modulation Issues (Option UNW)
Depending on the instrument model number a problem with pulse modulation
could be caused by different assemblies due to the different hardware
configurations. Refer to the section below for the model number being serviced
for information on isolating the cause of the problem.
N5166B, N5171B, N5172B, N5181B, N5182B
For these instruments the pulse generator and modulators are all contained on
the A3 RF assembly, so any pulse modulation failures will require the
replacement of the A3 RF assembly.
N5173B, N5183B
For these instruments the pulse generator is located on the A3 RF assembly
while there are two different modulators used, one on the A3 RF assembly and
one on the A7 Micro-Deck assembly. See Table 6-10 for information as to
which one is used for what frequency range.
9 kHz to <3.2 GHz
Since both the pulse generator and modulators used for pulse modulation in
this frequency range are contained on the A3 RF assembly, any pulse
modulation failures will require the replacement of the A3 RF assembly.
3.2 GHz to Max Frequency
Since the pulse generator and the modulator used for pulse modulation in this
frequency range are not contained on the same assembly the issue will need to
be isolated to the assembly causing the problem. Use the following procedure
to isolate the problem:
1. Return the instrument to a known state by pressing Preset.
2. Tune the instrument to a frequency at or above 3.2 GHz that is having the
problem by pressing FREQ, <frequency>.
3. Turn the RF on by pressing RF On/Off so that the LED below it comes on.
The instrument can use either an internal or an external pulse generator to
drive the pulse modulator. This troubleshooting procedure deals only with
the internal pulse generator. If there is a problem only when using a valid
external source, replace the A3 RF assembly.
Table 6-10 Pulse Modulation Control versus Frequency
Frequency Range Pulse Generator Pulse Modulator
9 kHz to < 3.2 GHz A3 RF Assembly A3 RF Assembly
3.2 GHz to Max Frequency A3 RF Assembly A7A3 Mod-Filter Assembly
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