Agilent Technologies 8564EC Service Manual page 411

Synthesizer Section
Unlocked Reference PLL (100 MHz VCXO)
8. If the 100 MHz oscillator is working, the reason for the unlocked
Check 10 MHz 9. On the spectrum analyzer, press
reference to
phase/frequency
10.Check the 10 MHz reference frequency-accuracy by connecting a
detector (steps
9-14)
11.If a 10 MHz signal >1 V peak-to-peak is not present at A15J301,
12.Measure the signal at TP301 with an oscilloscope. Refer to function
13.Measure the signal at U502 pin 11 with an oscilloscope. Refer to
14.If TTL-level signals (approximately 10 MHz) are not present, check
15.Measure the signals at the following test points with an active
Junction of C570 and C571
Junction of R715, R716,
U700 pin 3
U700 pin 1
16.If an approximately 10 MHz TTL signal is present at U502 pin 11
Check 17.Monitor U504 pin 5 and U503 pin 9 with an oscilloscope. These are
phase/frequency
detector (steps
17-22)
18.A locked loop will exhibit stable, narrow (approximately 20 ns wide),
538
condition is either a problem in the 10 MHz reference or a fault in
the signal path around the loop.
.
INT
frequency counter to A15J301 and verify that the reference
frequency is 10 MHz ±40 Hz after a 5 minute warm-up period.
refer to the "10 MHz Reference"
block M of A15 RF schematic (sheet 2 of 4).
function block X of A15 RF schematic (sheet 2 of 4). This signal
should be TTL levels at 10 MHz with a 60 percent duty cycle.
signals backwards through the loop to find a fault in the signal path.
probe/spectrum analyzer combination:
R567, and R568
with 60 percent duty cycle, and the RF portion of the phase-lock loop
is functioning, the fault probably lies in the phase/frequency detector
or the 100 MHz lock loop integrator.
the two outputs of the phase/frequency detector. Refer to function
block O of A15 RF schematic (sheet 2 of 4).
and positive-going TTL pulses occurring at a 10 MHz rate at U504
pin 5 and U503 pin 9.
,
AUX CTRL REAR PANEL
in Chapter 12 .
100 MHz, +2.5 dBm ±2 dB
100 MHz, −3 dBm ±2 dB
100 MHz, +16.5 dBm ±2 dB
100 MHz, +8.5 dBm ±2 dB
, and
10 MHz
Chapter 11