Low Band Problems - HP 8560A Service Manual

6. Check Al3 Second Converter mixer diode bias at A14J19 pin 1. The bias voltage should be
between -150 and -900 mVdc.
7. Troubleshoot the signal path. Refer to the power levels listed on Figure 11-3, RF Section
Troubleshooting.

Low Band Problems

displayed, refer to "Error Messages" in Chapter 6.
2. Perform External Mixer Amplitude Adjustment in Chapter 2. If this adjustment cannot
be completed, perform the steps located in "Third Converter" in this chapter.
3. Perform the First LO Output Amplitude performance test (Refer to the HP 8560A
Installation and Verification manual or use TAM functional test).
4. If the performance test fails, perform the First LO Distribution Amplifier adjustment
located in Chapter 2. If the adjustment fails, set the HP 8560A to the following settings:
C E N T E R F R E Q
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
5. Place the jumper on A14J23 in the TEST position. Remove W38 from the input of the
A7 LODA.
6. Use a power meter or another spectrum analyzer to measure the output of All YTO. The
power should be between +9 dBm and +13 dBm.
7. Reconnect W38 to the LODA. Place the jumper on A14J23 in the NORM position.
8. If ERR 334 ( unLevelled output) is present and the All YTO power output is correct, 1
the A7 LODA drive circuit may be defective. Refer to "A7 LODA (LO Distribution
Amplifier)" in this chapter.
9. Troubleshoot the signal path. Refer to the power levels listed on Figure 11-5, RF Section
Troubleshooting.
10. Check Third Converter as follows:
a. On the HP 8560A, press (PRESET) and set the controls as follows:
CENTER FREQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
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 Al5 RF Assembly.
REALIGN LO
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..300MHz
IF
. If any error messages are
RF Section 11-5