Agilent Technologies 8564EC, Service Manual

Page: 309 / 512

Chapter 8 399
ADC/Interface Section
A3 Assembly Video Circuits
3. Check that HODD (U408 pin 5) is a square wave with a period of
16.7 ms (2
×
sweep time/600).
4. Check LPOS_RST (U422 pin 4) for 200 ns low-going pulses every
128
µ
s.
5. Check LNEG_RST (A3U422 pin 12) for 200 ns low-going pulses
every 128
µ
s.
6. Set the detector mode to NORMAL and check that LNEG_RST
(A3U422 pin 12) has two pulses spaced 40
µ
s apart and then a single
pulse approximately 88
µ
s from the second pulse.
7. Check HMUX_SEL0 (A3U408 pin 3) and HMUX_SEL1 (A3U408 pin
9) according to Table 8-7 .
Rosenfell Detector
Refer to function block S of A3 Interface Assembly Schematic Diagram
(sheet 4 of 6) in the 8560 E-Series Spectrum Analyzer Component Level
Information.
If both HPOS_HLDNG and HNEG_HLDNG are high during the same
bucket, HROSENFELL will also be set high. This indicates that the
video signal probably consists of noise, since it rose and fell during the
same period. The HROSENFELL signal is valid only when the
NORMAL (rosenfell) detector mode is selected.
1. Remove anything connected to the 8564EC or 8565EC front-panel
INPUT 50
Ω
connector. Press
PRESET
on the spectrum analyzer and
set the controls as follows:
Center frequency ..................................................... 300 MHz
Span ................................................................................. 0 Hz
Sweep time .......................................................................... 5 s
Detector mode ......................................................... NORMAL
2. Check LPOS_RST and LNEG_RST as described in “Peak Detector
Reset” on page 398
Table 8-7 HMUX_SELO/1 versus Detector Mode
Detector Mode HMUX_SEL0
(U408 pin 3) HMUX_SEL1
(U408 pin 9)
NORMAL 15
µ
s pulse every
128
µ
s
40
µ
s pulse every
128
µ
s
SAMPLE H H
POS PEAK H L
NEG PEAK L H