HP 8560A, Руководство по обслуживанию

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Note
If the Transfer Roller Oscillator is locked, the address decoder is not at fault.
Address decoder
decodes a single address for both the Offset Oscillator
Pretune DAC and the Transfer Oscillator Pretune DAC.
9. If the pretune voltage is within the range listed in step 7, the Offset Oscillator is probably
at fault.
10. Measure the Offset Oscillator’s frequency at If the frequency is not 200 MHz
MHz, connect a frequency counter to pin 3 (using a oscilloscope probe).
Place the counter in the high-input impedance function.
11. Set the HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 Hz
12. Check that pin 1 is high. This indicates that prescaler is in the divide by 128
mode. Refer to function block AC of Al4 Frequency Control Schematic (sheet 5 of 5).
13. The signal’s frequency at pin 3 should be the Offset Oscillator’s frequency divided
by 128. The frequency would be 1.562500 MHz if the Offset Oscillator was locked at
200
MHz.
14. The amplitude of the signal at pin 3 should measure greater than 0.1 Vp-p.
Note Integrated circuit contains the reference and VCO dividers, phase
detector and modulus (pre-scaler) control circuitry.
15. Set the HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 Hz
16. Check that there are narrow pulses 400 apart at pin 18 (reference
divider output) and pin 15 (VCO divider output). Refer to function block AC of
Al4 Frequency Control Schematic (sheet 5 of 5).
17. Short pin 14 of the Offset Oscillator to pin 20. This sets the Offset
Oscillator’s TUNE+ line at V, setting the Offset Oscillator to its maximum
frequency.
18. The error voltage measured at Ulll pin 1 should be greater than Vdc.
19. Short pin 14 of the Offset Oscillator to ground. The error voltage at Ulll pin 1
should measure less than -9 Vdc.
Note Under some unlocked conditions, the Offset Oscillator loop may appear to
become unstable. (The error voltage will oscillate wildly.) This is normal
behavior brought on by the conduction of zener diodes VR308 and VR309
which short out R336 to improve the lock time.
20. Remove the shorts from
Synthesizer Section