HP 8560A, Service Manual

Page: 276 / 450

ADC Start/Stop Control
See function block B of A3 Interface Assembly Schematic Diagram (sheet 2 of 6).
The ADC Start/Stop Control determines the start time of all ADC conversions. Multiplexer
chooses the source of the start signal. Both HSTART-SRC and HBUCKET tell the
ASM to start a conversion.
1. Press on the HP 8560A and set the following controls:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60s
DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE
2. Check for a TTL high at pin 2 and a TTL low at pin 14.
3. Set the detector mode to NORMAL.
4. Check that pins 2 and 14 are both TTL low.
5. Set the HP 8560A to the following settings:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE
6. Check that pins 2 and 14 are both TTL high.
7. Press [CAL] and
REALIGN LO IF.
During the realignment, pin 2 should be
TTL low and pin 14 should be TTL high. If correct, the Start/Stop Control circuitry is
being selected properly by the processor and
in the ADC Register block is working
properly.
8. Press on the HP 8560A and set the controls as follows:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400ms
9. Check that pin 7 has positive 15 pulses with a 667 period (sweep
Check that pin 9 has negative 15 pulses with a 667 period
(sweep The pulses should be present during the sweep but absent during
retrace.
10. Set the detector mode to NORMAL.
11. Check that pin 9 has pulses every 130 and pin 7 has pulses every 333
(although pulse widths may be changing).
Section 7-23