Agilent Technologies 856290216 service manual Preselector Peaking Control Real Time DAC

Preselector Peaking Control (Real Time DAC)

Refer to function block H of A3 Interface Assembly Schematic Diagram in the

HP 8560 E-SeriesSpectrum 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