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Preselector Peaking Control (Real Time DAC)
Refer to function block H of A3 Interface Assembly Schematic Diagram in the
HP 8560 E-Series Spectrum Analyzer Component Level Information. The spectrum analyzer
uses a real-time DAC (R/T
DACl)
to peak the preselector.
1. Press (PRESET) on the spectrum analyzer and set the span to 0 Hz.
2. Connect a positive DVM lead to A3J400 pin 3 and the negative DVM lead to
A3TP4.
3. Press
(MKR),
[=CTRL),
TNTEZNAL
MIXER, and
PltESEL
MAN
ADJ
.
4. Monitor the DVM reading while changing the PRESELECTOR TUNE value from 0 to 255.
The PRESELECTOR TUNE value is the R/T
DACl
setting.
5. Check that the DVM reading increases from 0 to approximately
+lO
Vdc as R/T
DACl
is
set from 0 to 255.
6. If the voltage does not change as described, set the spectrum analyzer to single trigger
mode and check the following:
a. Check that A3U409B pin 18 is at -10 Vdc.
b. Check for the presence of pulses at
U409
pin 6 (IAO).
c. Check that pulses are present at
U409
pin 15 (LDAC2).
d. Check that pulses are present at
U409
pin 16 (LWRCLK).
7. If the LDAC2 or LWRCLK signals are incorrect, refer to “Interface Strobe Select” in this
chapter.
8-12
ADC/lntertace
Section