R&S CMU Troubleshooting
1100.4903.82 3.75 E-5
• Fault: Short-circuit of one or several operating voltages
Check LEDs (H1 to H8) at the bottom of MOTHERBOARD1 to determine which voltage is short-
circuited.
Note: In the case of a short-circuit, the power supply switches off all voltages after a short period
of time.
Restart is possible using the ON/STANDBY key.
Pull out individual
modules and repeat
test. Faulty module
found?
Yes
POWER SUPPLY
or
M
OTHERBOARD
faulty!
No
Respective module
faulty!
• Fault: Instrument fan does not work.
+12 VFAN voltage
present (LED H5 at
MOTHERBOARD
illuminated)?
Protective cir-
cuit of instrument fan
at MOTHERBOARD1
has switched off fan
voltage?
Yes
Yes
POWER SUPPLY faulty
or voltage at
MOTHERBOARD
short-circuited!
Fan faulty!
Instrument fan blocks
or instrument fan
current consumption
too high!
No
No
Note: Measure instrument fan voltage at connector X 211! By pressing the STANDBY/ON key again,
the protective circuit of the instrument fan can be restarted.
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