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 A3U509 chooses the source of the start signal. Both
1. Press (ml on the HP 8560A and set the following controls:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60s
DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE
2.Check for a TTL high at A3U509 pin 2 and a TTL low at A3U509 pin 14.
3.Set the detector mode to NORMAL.
4.Check that A3U509 pins 2 and 14 are both TTL low.
5.Set the HP 8560A to the following settings:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE
6.Check that A3U509 pins 2 and 14 are both TTL high.
7.Press [CAL] and REALIGN LO & IF. During the realignment, A3U509 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 U508 in the ADC Register block is working properly.
8.Press (PRESET) on the HP 8560A and set the controls as follows:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400ms
9.Check that A3U509 pin 7 has positive 15 ps pulses with a 667 pus period (sweep time/600). Check that A3U509 pin 9 has negative 15 ~LS pulses with a 667 ps period (sweep time/600). The pulses should be present during the sweep but absent during retrace.
10.Set the detector mode to NORMAL.
11.Check that A3U509 pin 9 has pulses every 130 11s and U509 pin 7 has pulses every 333 ps (although pulse widths may be changing).
ADC/lnterface Section