R&S ZVA8, Service Manual

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R&S ZVA Repairs
1177.5333.02 3.121 E-11

Enter service function 2.21.2.18.17512345 (IF = 17.512345 MHz).

Disable level corrections with SF 2.21[..24].2.15.1
If the level displayed on the ZVA's screen is not within the range -4 dBm ± 2 dB, the board must be
replaced.
Testing the Motherboard
28 V supply
Using a multimeter, measure the voltage at X 100.B5 (wrt ground).
Permissible deviation: ± 0.5 V
Preamplifier for DC measurement inputs
Apply the DC voltages listed in the table using the 4-pin Mini-DIN connector at the DC measurement
input.
Measure the DC voltage with a multimeter.
Input Voltage at Gnd ApPlied voltage Measurement at Rated value
DC MEAS -1 V to +1 V 8 3, 5, 6 - 1 V X 141.B10 2.33 V
DC MEAS -1 V to +1 V 6 3, 5, 8 + 1 V X 141.B11 2.33 V
DC MEAS -10 V to +10 V 8 3, 5, 6 - 10 V X 141.D10 2.33 V
DC MEAS -10 V to +10 V 6 3, 5, 8 + 10 V X 141.D11 2.33 V
Fig. 3-11 Pin assignment DC MEAS connector
If the measured value is more than 10% above or more than 10% below the stated nominal value, the
motherboard must be replaced.