Troubleshooting R&S SMB
1407.0806.82 3.8 E-6
Switch-On Problems
The yellow LED on the front panel, next to the ON/OFF Button is directly connected to the Standby
Voltage of the power supply (via a resistor on the Basis Board) and is therefore a good indicator of the
basic working of the power supply.
When the instrument is switched on, the following modules are involved:
• Power supply
• Basis Board
• Switching pad
To analyze switch-on and switch-off problems that occur with the R&S SMB, the interplay of the individual
modules is summarized in the following.
Switch-on
When the ON/OFF button on the front panel is pressed, the signal on the signal on the ON/OFF test point
(1406.6600.02: pin 21 of X112, switching pad connector) goes low. In this case the Basis Board pulls the
signal on pin 13 of X101 (power supply connector see Fig. 3-5) low, which in turn switches on the power
supply. In case of a prior emergency shutdown (pressing the ON/OFF Button for more than 5 seconds) it
may take a few seconds until this mechanism works again.
Within four seconds after switch-on, the CPU takes over the control of pin 13 of the power supply
connector. If the green LED on the front panel lights up for only a short time (approx. five seconds) and
then the orange standby LED lights up again, this means that the CPU is not booting properly. The cause
may be a defective or overheated power supply or Basis Board.
• Error: Instrument cannot be switched on.
Action Possible error causes and further steps
Check power-on switch on the rear.
Check fuses on the rear.
Power switch OFF: Switch on power supply.
Check yellow LED (standby).
LED remains unlit:
Measure standby voltage at pin1 X101 (see Fig. 3-1).
Rated value: 4.75 V… 5.25 V
No voltage: Check power cable from power supply.
no/faulty voltage: change power supply
Otherwise: Loose Cable W112 or bad contact of
switching pad.
To Next Page
Loading...
