HP 70908A, Руководство по обслуживанию

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If Y ou Have V erication T est F ailures
If T est 05. 10.7 MHz Rejection F ails
If any 10.7 MHz rejection routines fail, the problem is most likely the A11 last converter
321.4 MHz bandpass lter or 10.7 MHz trap (A11C28, A11L10).
T o solve this problem:
1. Troubleshoot the A11 last converter.
2. If necessary , obtain service from Hewlett-P ackard. (Refer to \If Y ou W ant Hewlett-P ackard
to Service Y our RF Section " in Chapter 1.)
If T est 06. F eedthrough Out 21.4 MHz P ort F ails
If any 21.4 MHz output feedthrough routines fail, the failure is most likely the lters in the IF
path.
T o solve this problem:
1. Check the stop-band response of all the lters in the IF path.
2. If necessary , obtain service from Hewlett-P ackard. (Refer to \If Y ou W ant Hewlett-P ackard
to Service Y our RF Section " in Chapter 1.)
If T est 07. Harmonics Out 21.4 MHz P ort F ails
This test checks the overall lter response of the HP 70908A RF section IF output.
If any 21.4 MHz output harmonics routines fail, the failure is most likely caused by
A11 last converter.
T o solve this problem:
1. Check that no RFI gaskets are missing from covers and underneath printed circuit boards .
2. If test falls within the test limits of the 21.4 MHz output port, troubleshoot the
A11 last converter . (Refer to \Troubleshooting the A11 Last Converter".)
3. If test does not fall within the test limits , check the IF path until the faulty assembly is
found.
4. If necessary , obtain service from Hewlett-P ackard. (Refer to \If Y ou W ant Hewlett-P ackard
to Service Y our RF Section " in Chapter 1.)
If T est 08. Residual Emissions Out 21.4 MHz P ort F ails
This test checks for N x 300 MHz and LO feedthrough emissions from the rear panel 21.4 MHz
output.
If any 21.4 MHz output residual emissions response routines fail, analyze the failure to
determine the location of the malfunction.
T o solve this problem:
1. If the N x 300 MHz emissions test fails , troubleshoot the A11 last converter (either the
diplexer circuit out of the mixer or the 21.4 MHz output bandpass lter). Ensure that the
polyiron gasket is installed in the A11 last converter casting.
2. If the LO feedthrough test fails , verify that the LO signal is 15 dBm at the input of
A15 RF 1st converter.
3. If the power level is correct, replace the A15 RF 1st converter.
4. If the power is too high, perform A djustment 04. LOLA P ower Out.
5. If necessary , obtain service from Hewlett-P ackard. (Refer to \If Y ou W ant Hewlett-P ackard
to Service Y our RF Section " in Chapter 1.)
T roubleshooting 4-17