Chapter 12 601
RF Section
Low and High Band Problems
Low and High Band Problems
1. On the spectrum analyzer, press PRESET and REALIGN LO &
IF. If any error messages are displayed, refer to “Error Messages” in
Chapter 7 .
2. Perform "External Mixer Amplitude Adjustment" in Chapter 3. If
this adjustment cannot be completed, perform the steps located in
"Third Converter" in this chapter.
3. Perform the "1st LO OUTPUT Amplitude" performance test in the
calibration guide.
4. If the performance test fails, perform the "LOMA Adjustments"
using the adjustment/diagnostic software.If the adjustment fails, set
the spectrum analyzer to the following settings:
Center frequency .................................................. 300MHz
Span ..............................................................................0Hz
5. Place the jumper on A14J23 in the TEST position. Remove W38 from
the input of A7.
6. Use a power meter or another spectrum analyzer to measure the
output of A11 YTO. The power should be between +2 dBm and
+13 dBm.
7. Reconnect W38 to A7. Place the jumper on A14J23 in the NORM
position.
8. If ERR 334 (unlevelled output) is present and the A11 YTO power
output is correct, the A7 drive circuit may be defective. Refer to “A7
LO Multiplier and Distribution Amplifier” on page 602.
9. Troubleshoot the signal path. Refer to the power levels listed on
Figure 12-11 on page 631, RF Section Troubleshooting Block
Diagram.
10.Check Third Converter as follows:
a. On the spectrum analyzer, press
PRESET and set the controls as
follows:
Center frequency ............................................. 300MHz
Span .........................................................................0Hz
b. Inject a −28 dBm, 310.7 MHz signal into A15J801.
c. If a flat line is displayed within 2 dB of the reference level, but the
External Mixer Amplitude Adjustment fails, troubleshoot the A15
RF Assembly.
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