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

1.On the HP 8560A press (-1 and REALIGN LO & IF . If any error messages are 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300MHz 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 ( unLevelled1 output) is present and the All YTO power output is correct, 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.

RF Section 11-5