Rohde & Schwarz FSP3 Service Manual page 192

Troubleshooting
Signal Paths on the IF Filter Board
The RF attenuator is used to provide an appropriate test level. Therefore, a fault in the RF attenuator will
entail subsequent errors with the IF filter test.
Normal action
Input Level of IF Filter / Calibration Amplifier
(CAL-Amps 1 + 2)
Selftest detector A (see block diagram)
The level applied to the RF input is referred to as
mixer level in the following. The RF attenuation is
to be set to 0 dB. The input frequency is always
128 MHz.
The input level at X131 is 8 dB ±3 dB higher than
the mixer level. With maximum mixer level of
-10 dBm the level at X131 is -2 dBm ± 3 dB.
CAL_Amp2 is provided for frequency response
correction. With the input frequency of 128 MHz,
the gain of CAL_Amp2 is set to 0 dB. The
frequency for the selftest is 128 MHz.
The nominal gain between X131 and X132 is
+2 dB.
The level at X132 is 0 dBm with a mixer level of
-10 dBm.
The selftest (A) checks the level to ±5 dB (User)
or ±3 dB (Service Level 1) after passing the
CAL_Amps.
1164.4556.82
Error and error cause
FATAL ERROR!
IF Board: IF input level / CALAMP
Selftest aborted
Possible error causes:
•
Signal path interrupted in the frontend.
•
Erroneous EEPROM data in the frontend
leading to incorrect setting of CAL_Amp1.
•
CAL_Amp1 or 2 faulty.
Troubleshooting
Check the level applied at X131 with
mixer level -10 dBm: -2 dBm, production
tolerance ± 3 dB, maximum tolerance
permitted ± 4.5 dB;
Replace the frontend, if the deviation exceeds
this value
3.88
R&S FSP
E-1