HP 8560A, Руководство по обслуживанию

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21. Set the HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22. Check that the voltage at U112 pin 5 is the same as that on U112 pin 3.
23.
Set the HP 8560A to a SPAN of 100
Note
is a sample-and-hold IC that stores the phase-lock error voltage
during offset sweeps Refer to Function Block AD of Al4
Frequency Control Schematic (sheet 5 of 5). When the loop is locked, U112 is
in the hold mode and U112 pin 8 should be low.
24. Trigger a dual-trace oscilloscope from U112 pin 8 (OFFHOLD), and observe the
sample-and-hold action on U112 pins 3 and 5.
25. If 302 or 327 are displayed and the Offset Oscillator loop is locked, troubleshoot
Roller MUX MUX Amp U328, and MUX Gain Control Switch Refer to
function block AG in Al4 Frequency Control Schematic (sheet 5 of 5).
26. If U328, and are working properly, suspect a malfunction of the A3 Interface
assembly or the W2 Control Cable.
Transfer Oscillator PLL
The Transfer Oscillator PLL provides a synthesized signal from 65 MHz to 110 MHz in
50
steps. This signal mixes with the Main Roller output, producing the roller IF at
approximately 2 MHz. The roller IF is compared to the Offset Oscillator’s divided output to
phase-lock the main-roller oscillator.
1. Use an active probe (or sniff loop) connected to a spectrum analyzer to test for an output
from the Transfer Oscillator. The amplitude at TP301 should be approximately
-4 Refer to function block AI of Al4 Frequency Control Schematic (sheet 5 of 5).
2. The voltage at pin 1, XFER OSC BIAS, should m7.5 Vdc V.
3. If the Transfer Oscillator’s output contains noise sidebands, phase noise, or jitter,
troubleshoot switches Q102 and Q103 in function block AK and in function block
AN.
4. Set the HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5. If the Transfer Oscillator’s frequency at TP301 is 96.7 MHz MHz, the oscillator is
unlocked. Refer to function block AI of Al4 Frequency Control Schematic (sheet 5 of 5)
in the Component-Level Information binder.
6. If the Transfer Oscillator frequency is not within the range in step 5, short
pin 12.
7. If the Transfer Oscillator frequency is not 96.7 MHz MHz, check that the Transfer
Oscillator pretune voltage at J302 pin 13 is Vdc +/-1.8 V.
Synthesizer Section