Rohde & Schwarz FSP3 Service Manual page 189

R&S FSP
Testing the Reference Signals on Standard Frontend (Modules 1 and 2) and on
the IF Filter Module
Errors detected do not cause abortion of the test. However, the subsequent checking of the signal path
in the IF filter and detector boards is skipped, since there is no local oscillator provided to convert the
128-MHz calibration signal to the 20.4-MHz IF required for the tests.
Normal action
Reference Signals on the IF Filter Board
Figure 3-5 illustrates the reference signals on the
IF-filter board.
The selftest points are emphasized by color. The
levels are measured at these points with a
permitted tolerance of ±5 dB.
In addition, the level control loop of the calibration
signal generator is monitored. If the loop unlocks,
the level of the calibration signal is not accurate,
even if no error occurs at the other test points.
Channel Test
1 128 MHz input level
2 10 MHz output level
3 Calibration signal level
4 Control voltage of calibration signal
128 MHZ Input level:
The transfer level should be > –5 dBm. It can be
rechecked at the output X114 of the frontend.
10 MHZ Output level:
This is the reference frequency for synchronizing
all oscillators
1164.4556.82
Error and error cause
FATAL ERROR!
IF Board: 128 MHz Reference input level low.
Selftest aborted
If this signal is missing, the clock for the
detector board is missing, too. If the level is
too low, proper functioning cannot be assured.
Replace Frontend Module 2, if any error
occurs.
ERROR!
IF Board: 10 MHz Reference output level low,
TCXO / OCXO.
If the signal fails, the instrument continues
functioning properly, however, the frequency
accuracy is violating the tolerance limits.
Option OCXO fitted:
Check output level of option
(10 MHz, > -5 dBm).
If the level is o.k., the IF-filter board is faulty.
Replace IF-filter board
Option OCXO not fitted:
Replace IF-filter board
3.85
Troubleshooting
E-1