Adc Mux - Agilent Technologies 8564EC Service Manual

ADC/Interface Section
A3 Assembly Video Circuits
3. Check A3U423 pin 4 for two low-going 3.3 µs pulses 40 µs apart
occurring every 130 µs.
4. Check that HROSENFELL (A3U610 pin 6) has two pulses spaced
approximately 40 µs apart and then a third pulse 60 µs from the
second pulse. Each pulse should be approximately 10 µs wide and
low-going.
5. Monitor HROSENFELL with an oscilloscope while reducing the
video bandwidth from 1 MHz to 1 kHz.
6. As the video bandwidth is decreased to 1 kHz, the HROSENFELL
line should increasingly show a low logic level. With a video
bandwidth of 1 kHz, a nearly flat line should be displayed on the
CRT.
7. Set the sweep time to 50 ms. Externally trigger the oscilloscope
using the spectrum analyzer rear panel BLKG/GATE OUTPUT.
8. Check that HPOS_HLDNG (A3U416 pin 4) is mostly high with a
1 MHz video bandwidth and mostly low with a 1 kHz video
bandwidth.
9. Check that LNEG_HLDNG (U408A pin 13) is mostly high with a
1 MHz video bandwidth and mostly low with a 1 kHz video
bandwidth.

ADC MUX

Refer to function block AA of A3 Interface Assembly Schematic
Diagram (sheet 6 of 6) in the 8560 E-Series Spectrum Analyzer
Component Level Information.
The ADC MUX switches various inputs into the video path for
conversion by the ADC. The SCAN RAMP input is used during sweeps
having a width of equal to or greater than 2.01 MHz times N, to control
the timing of the ADC operations. Some combination of MOD_VIDEO,
NEG_PEAK, and POS_PEAK is used for the video signal to be
converted by the ADC. The YTO ERR, FCMUX, CAL OSC TUNE, and
OFL ERR inputs are used only during diagnostic and auto adjust
routines and during retrace.
1. Set the spectrum analyzer to the following settings:
Center frequency .................................................. 300 MHz
Span .............................................................................. 0 Hz
Reference level ....................................................... −10 dBm
Sweep time .................................................................... 50 s
DETECTOR MODE ............................................. SAMPLE
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