Troubleshooting R&S SMB
1407.0806.82 3.22 E-6
Pin at X101 Test Point Fuse
R&S SMB in stand by mode R&S SMB switched On
5…10 +5V F7 0 V +4.7 V … +5.3 V
5…10 +5V_IQ F4 0 V +4.7 V … +5.3 V
3, 4 +12V F3 0 V +12.4 V … +14.2 V
3, 4 +12V_IQ F5 0 V +12.4 V … +14.2 V
2 -12V_IQ F6 0 V -14.2 V … -12.4 V
+3V3 0 V +3.1 V … +3.5 V
+28V 0 V +26.6 V … + 29.4 V
+2V5 0 V +2.38 V … +2.63V
+1V2 0 V 1.14 V … 1.26 V
1 +4.5 V … + 5.5 V Standby +4.5 V … + 5.5 V Standby
13 > +3 V < 0.8 V
14…20 GND GND
Fig. 3-5 Power Supply Connector of the Basis Board (1406.6600.02)
Fuses
Switch on the R&S SMB and measure the voltage drop across the fuses F3 – F7 (yellow marked see Fig.
3-5) with a multimeter. The voltage across every fuse should be in the range -100 mV … +100 mV. The
fuses might be blown due to a defective module other than the Basis Board. If one of the fuses is blown
replace the fuse with the correct type given below. Remove connection W222 to the RF Board and W113
to the display. Switch on the R&S SMB and check the voltage drop across the fuses after two minutes
again. If one of the fuses is blown again the Basis Board is defective. If the fuses are OK switch off
R&S SMB again and then connect the display and switch on the R&S SMB again. If one of the fuses is
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