Rohde & Schwarz SMB100A - Page 157

Troubleshooting R&S SMB
1407.0806.82 3.18 E-6
Fault Test Action if test fails
10 MHz
Reference
Output faulty
R&S SMB setting:
• Setup  Reference internal
Measure 10 MHz reference output signal with
spectrum analyzer or frequency counter and
power meter. Output frequency and level have
to meet the specifications given in the data
sheet.
R&S SMB without Reference
Oscillator R&S SMB-B1:
Most probably the RF Board is
defective. Check the RF Board
being supplied correct (see
page 3.24).
R&S SMB with Reference Oscillator
R&S SMB-B1:
Remove the Reference Oscillator
B1 (see page 3.57) and perform this
test again. If still failing most
probably the RF Board is defective.
Check the RF Board being supplied
correct (see page 3.24).
If the 10 MHz reference signal is in
tolerance most probably the
Reference Oscillator B1 is defective.
Check this module being supplied
correct (see page 3.30).
R&S SMB settings:
• LFGen Stat on
• LFGen Source Impedance Low (only
available on newer RFBOARDS)
• LFGen Freq 50 Hz
Measure the output voltage of the LF signal
output with an AC-multimeter. The RMS
reading should be 0.707V ± 0.05 V.
Check the connection of cable
W215 to the RF Board (see
Removing the RF-Board).
If it is connected correct most
probably the RF Board is defective.
Check the RF Board being supplied
correct (see page 3.24).
LFGen Output
Faulty
R&S SMB settings:
• Setup  Reference internal
• LFGen Stat on
• LFGen Level 1 V
• LFGen Frequency 100 kHz
Attention: LF specification applies to loads
greater or equal 200 K only!
Check the level at the ‘LF’-BNC Connector
with an oscilloscope or voltage meter. Check
the frequency and harmonic distortion with an
oscilloscope with FFT functionality or with a
spectrum analyzer with high input impedance
(i.e. with a 150 K series resistor).
Most probably the RF Board is
defective. Check the RF Board
being supplied correct (see
page 3.24).
MOD ext Input
Faulty
R&S SMB settings:
• Setup  Reference internal
• AM State on
• AM Source external
• Ext Impedance High (only available on
newer RFBOARDs)
Measure the input resistance of the Mod Ext
BNC connector signal with a multimeter. The
input resistance should be 221 kK ± 20 %.
Check the connection of cable
W214 to the RF Board (see
Removing the RF-Board).
If connected correct most probably
the RF Board is defective. Check the
RF Board being supplied correct
(see page 3.24).