HP 8560A, Service Manual

Page: 273 / 450

Detector Mode
SAMPLE
POS PEAK
NEG PEAK
Table 7-9. Logic Levels at
pin 1 pin 15 pin 16
H L
H
H L
L
L H H
5. Set the HP 8560A to the following settings:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50ms
6. Check for the presence of the SCAN RAMP signal by connecting an oscilloscope probe to
pin 45 ( component side of Connect the negative-probe lead to
7. A 0 to 10 V ramp should be present in both LINE and FREE RUN trigger modes. If the
waveform is present only in LINE trigger, ADC control signal HBADC-CLKO may be
faulty. Refer to “ADC Control Signals” in this chapter.
8. If the scan ramp is present, but is not being switched to the output of replace
If the scan ramp is absent in either mode, do the following:
a. Connect the oscilloscope probe to pin 15 (HSCAN).
b. A TTL signal (high during 50 ms sweep time and low during retrace) should
be present, indicating A3 is working properly. Refer to the Synthesizer Section
troubleshooting procedure. A faulty TTL signal indicates a bad A3 Interface assembly.
9. Set the HP 8560A to the following settings:
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IF Adjust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
10. Check for the presence of the CAL OSC TUNE signal by monitoring pin 25 with
an oscilloscope. If ERR 499 CAL UNLK is displayed and a signal greater than 10 V
peak-to-peak during part of the retrace period, is present, the fault is on the A3 assembly.
11. If a constant dc voltage is present during the sweep and all of the retrace period, refer to
the IF Section troubleshooting procedure.
7-20 Section