288 Keysight N9038A MXE Service Guide
Front End Control
A15 Front End Control Assembly Troubleshooting
A12 YTF Preselector Control - (Option 508 & 526 only)
A problem with the A12 YTF Preselector assembly could be caused by either a
failure of the assembly itself, the control logic sent to it, or damage to the cable
between the two. This section will verify the functionality of the control logic
coming from the A15 Front End Control assembly. If after verifying that the
control logic in working properly refer to Chapter 6, “RF Downconverter
Section.” for further troubleshooting information on the A12 YTF Preselector
assembly itself.
This section will verify the control signals from the A15 Front End Control
assembly to the A12 YTF Preselector assembly. There are only three controls
for the A12 YTF Preselector:
1. Serial Communication for Assembly Identification
2. Supply Voltage for Serial Communications
3. Main Coil Current
The status of the supply voltage and main coil current can be measured on the
Front End Control Test board assembly with the use of three test points, J31,
P8 Pin 1, and P8 Pin 2, as seen in Figure 8-11.
Figure 8-11 A12 YTF Preselector Control Front End Test Board
When making Main Coil Current measurements R119, R120, and R121 on the Front End Control
Test board can get VERY HOT. Be careful not to touch them or place any combustible objects in
contact with them. Also, do not clip test leads to P8 and leave the instrument unattended while
powered on.
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