Adc Start/Stop Control - HP 8560E Service Manual

ADC/Interface Section
A3 Assembly ADC Circuits
the frequency counter in Chapter 9.
12.Reconnect A3W1 to A2J2.

ADC Start/Stop Control

Refer to function block B of A3 Interface Assembly Schematic Diagram
(sheet 2 of 6) in the
HP 8560 E-Series Spectrum Analyzer Component Level
.
Information
The ADC Start/Stop Control determines the start time of all ADC
conversions. Multiplexer A3U509 chooses the source of the start signal.
Both HSTART_SRC and HBUCKET tell the ASM to start a conversion.
1. Press on the HP 8560E/EC and set the following controls:
PRESET
Span ................................................................................. 0 Hz
Sweep time ....................................................................... 60 s
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 8560E/EC to the following settings:
Span ............................................................................. 1 MHz
Detector mode .......................................................... SAMPLE
6. Check for a TTL high at A3U509 pin 2 and a TTL low at A3U509 pin
14.
7. Press and
CAL REALIGN LO &IF
pin 2 should be TTL low and pin 14 should be TTL high until the 10
kHz and narrower resolution bandwidths are adjusted. 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 on the HP 8560E/EC and set the controls as follows:
PRESET
Span .................................................................................... 0 Hz
Detector mode ............................................................. SAMPLE
Sweep time .................................................................... 400 ms
9. Check that A3U509 pin 7 has positive 15 µs pulses with a 667 µs
period (sweep time/600). Check that A3U509 pin 9 has positive 15 µs
pulses with a 667 µs 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 µs and U509 pin 7
has pulses every 667 µs (although pulse widths may be changing).
382
. During the realignment, A3U509
Chapter 7