Rohde & Schwarz 1164.4391.03, Service Manual

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R&S FSP Troubleshooting
1164.4556.82 3.91 E-1
Troubleshooting Frontend 1
Depending on the kind of error a few measurements should be performed on the frontend prior to
replacing the module:
•
IP3 too high
•
Signal level too low
•
LO feedthrough too high
•
Spurious signals
Depending on the kind of error a few measurements should be performed on the frontend prior to
replacing the module.
Very high values with input frequency 0, > -10 dBm with an input attenuation of 0 dB indicate that the
mixer does not work properly.
Action Error and error cause
Measure with diode tester at X101:
rated value: 0.35 V voltage in the forward and
reverse directions with a current of
1 mA.
Different values in both directions, high-impedance
or very low-impedance:
mixer defective :
replace frontend1
•
Signal missing or displayed with incorrect frequency
If the signal is missing or the instrument signals "LOUNL", the conditioning of the 1st LO is probably not
correct. The function of this oscillator requires both, the EEPROM data and the reference frequency of
the second module.
Action Error and error cause
Measure function of the 1st LO in zero span.
check signal at X102:
rated value: 3476.4 MHz above the current
input frequency (between 0 Hz and
3 GHz) and the signal level is
approx. –5 dBm.
The frequency is considerably higher or lower or
the signal is not stable
frontend 1 defective
replace Frontend 1