76 Chapter 3
Troubleshooting the RF Section (E4440A, E4443A, E4445A)
RF Section Description (E4440A, E4443A, E4445A)
A14 and A15 Step Attenuators
A faulty attenuator can cause improper signal level in both High and
Low bands, often in certain combinations of attenuator settings. In
addition, a faulty A14 can prevent the frequency range from going down
to 3 Hz, even when the PSA is set in DC Coupled mode. A14 can also
prevent the 50 MHz calibrator signal from being displayed.
Figure 3-4 Attenuator Block Diagram
The attenuators receive control signals and supplies from the A13
Front End Driver assembly. A14 is fed from A13J3 and A15 is fed from
A13J4. Ground is on pin 3 and the 25V supply is on pin 10. Viewing
from the circuit side of the board, the connector pinouts are shown:
Figure 3-5 Connector Pinout
If the 50 MHz calibrator signal is not displayed, first verify its presence
at A14J2. Disconnect the gray W20 cable from the attenuator and
monitor the signal coming out of the cable with another spectrum
analyzer. The signal should be 50 MHz at –25 dBm. Verify that the
attenuator is receiving the proper TTL signals monitoring the points on
A13J3 with a scope using the truth table.
Input Path Calibrator Path Select
J3 pin 2
Calibrator Path Bypass
J3 pin 1
RF High Low
Calibrator Low High
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