Transfer Oscillator Pll - HP 8560A Service Manual

21. Set the HP 8560A to the following settings:
C E N T E R F R E Q
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
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 kHz.
Note
during offset sweeps (5100 kHz). 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 ERRS 302 or 327 are displayed and the Offset Oscillator loop is locked, troubleshoot
Roller MUX U305, MUX Amp U328, and MUX Gain Control Switch U326B. Refer to
function block AG in Al4 Frequency Control Schematic (sheet 5 of 5).
26. If U305, U328, and U326B 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 kHz steps. This signal mixes with the Main Roller PLL's 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 A14A102 Transfer Oscillator. The amplitude at TP301 should be approximately
-4 dBm. Refer to function block AI of Al4 Frequency Control Schematic (sheet 5 of 5).
2. The voltage at A14J302 pin 1, XFER OSC BIAS, should measure +7.5 Vdc fl 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 Q104 in function block
AN.
4. Set the HP 8560A to the following settings:
C E N T E R F R E Q
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
5. If the Transfer Oscillator's frequency at TP301 is 96.7 MHz f2 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 A14A102
pin 12.
7. If the Transfer Oscillator frequency is not 96.7 MHz fl MHz, check that the Transfer
Oscillator pretune voltage at J302 pin 13 is t13.6 Vdc +/-1.8 V.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
Synthesizer Section lo-35