Agilent Technologies HP 8719D Service Manual page 240

Note
While adjusting the DAC numbers in the following step, monitor
port 1 with a spectrum analyzer to be sure that the frequency
remains between 50 MHz and 1.1 GHz. DAC numbers that set
the analyzer below 50 MHz should not be used.
If greater than -5 dBm for DAC numbers from 50 MHz (DAC # -3650) to
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about 1.1 GHz (DAC # = 4095), troubleshoot the cabling from S2J3 to the R
sampler A6452 (refer to the overaIl block diagram).
If less than -5 dBm at S2J3, the problem is in the A53 mixer/amp, A57
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fixed oscillator, S2, or S3.
3. Measure power at the A53 end of cable W6.
If power is greater than + 8 dBm, S3 is good.
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If power is not good, replace S3.
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4. Measure power on the S2 end of W36.
If the power is greater than -5 dBm, replace S2.
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If the power is less than -5 dBm, the problem is the A53 mixer amp or
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the A57 fixed oscillator. Replace the A53 first and if the problem persists,
replace the A57.
Mid Band Problems: (HP 8722D Only)
1. Press (mj &@&I$ m $l$I&Vic& h&I&$ 'Sge,:&&$$ .:&#II
tuning the instrument from about 2.4 to 5 GHz). Loss of lock in mid band
only may likely be due to a bad cable or connection.
2. Referring to the overall block diagram, the following components may be at
fault:
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