Table 7-9 Logic Levels At A3U108 - HP 8560E Service Manual

Table 7-9 Logic Levels at A3U108
SAMPLE
POS PEAK
NEG PEAK
5. Set the HP 8560E/EC to the following settings:
6. Check for the presence of the SCAN RAMP signal by connecting an
7. A 0 to 10 V ramp should be present in both LINE and FREE RUN
8. If the scan ramp is present, but is not being switched to the output of
9. Set the HP 8560E/EC to the following settings:
10.Press
11.If a constant dc voltage is present during the sweep and all of the
Chapter 7
in Chapter 10.
Detector U108 pin 1
Mode
H
H
L
Span .......................................................................... 5 MHz
Sweep time ................................................................. 50 ms
oscilloscope probe to A3J2 pin 45 (component side of A3J2). Connect
the negative-probe lead to A3TP4.
trigger modes. If the waveform is present only in LINE trigger, ADC
control signal HBADC_CLK0 may be faulty. Refer to "ADC Control
Signals" in this chapter.
U108, replace U108. If the scan ramp is absent in either mode, do
the following:
a. Connect the oscilloscope probe to A3J400 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 in
Chapter 10. A faulty TTL signal indicates a bad A3 Interface
assembly.
Sweep time ............................................................... 100 ms
Span ...................................................................... 100 MHz
and
CAL IF ADJ ON
TUNE signal by monitoring A3J401 pin 25 with an oscilloscope. If
ERR 499 CAL UNLK is displayed and a signal within the range of
−10 V to +10 V is present during part of the retrace period, the fault
is on the A3 assembly.
retrace period, refer to the IF Section troubleshooting procedure in
Chapter 8.
U108 pin 15 U108 pin 16
L H
L L
L H
and check for the presence of the CAL OSC
ADC/Interface Section
A3 Assembly Video Circuits
379