HP 70908A, Service Manual

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If Y ou Have V erication T est F ailures
If T est 17. Step Gain F ails
If any step gain routines fail, the failure is most likely caused by A11 last converter.
T o solve this problem:
1. P erform A djustment 24. Last Converter Bandpass Filter .
2. If the test still fails , troubleshoot the A11 last converter . (Refer to \Troubleshooting the
A11 Last Converter").
3. 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 18. Gain Compression F ails
If any gain compression routines fail, the failure is most likely caused by A11 last converter .
T o solve this problem:
1. Check the IF output at the rear panel 321.4 MHz output port. (The 321.4 MHz output must
be enabled.)
2. If gain compression cannot be seen at that port, troubleshoot the A11 last converter.
3. 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 19. A ux LO P ower and Harmonics F ails
If any LO output power and harmonics routines fail, the failure is most likely caused by
A1 leveling amplier .
T o solve this problem:
1. P erform A djustment 01. LOLA Gate Bias , A djustment 04. LOLA P ower Out, and A djustment
05. LOLA Tuned Filter .
2. If the test still fails its limits , troubleshoot the A1 leveling amplier .
3. If A1J3 or A1J4 are heavily loaded down, this test may also fail.
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 20. Diagnostics F ails
In order to run this test, all loops must be able to lock and all error bits must show no errors .
In general, this test causes conditions that toggle each error-reporting bit from a \no error" to
\error" state . The power supply fault bit is not tested.
Use the following information when troubleshooting this failure .
LO unleveled
This test veries that the LO leveling loop is leveled with a 5 dBm LO input power to the
HP 70908A RF section and that it is unleveled with a power less than 5 dBm.
T o solve this problem:
1. Troubleshoot a 7002 error code .
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.)
4-20 T roubleshooting