Agilent Technologies 856290216 service manual Check First LO pretune frequency and amplitude steps

5.Calculate the YTO frequency error by subtracting the frequency recorded in step 3 from the frequency recorded in step 4. Record the result below:

YTO Frequency Error = M H z

YTO Frequency Error = YTO Frequency (MEASURED) -YTO Frequency(cALcuLATED)

6.On the spectrum analyzer, press M#RE 1 OF 2, FRIQ I3IKlKlSE, and FR&C IV FREq . Record the fractional N frequency below:

Fractional N frequency = MHz

Caution Replacement of the phase/frequency detector chip A14U204 is not recommended. The part is very delicate and requires special tooling to install successfully.

7.If the YTO frequency error recorded in step 5 is greater than 20 MHz, do the following:

a.Check the YTO Adjustments using the TAM or the procedure in Chapter 2, “Adjustment Procedures.”

b.Check the YTO DACs using the procedure in steps 41 through 49 below, or using manual probe troubleshooting with the TAM on A14J17 and A14J18.

c.Refer to steps 9 through 34 below.

8.If the YTO Frequency error recorded in step 5 is less than 20 MHz, do the following:

a.Measure the frequency at A14J304. The frequency should be equal to the frequency recorded in step 6. If not, refer to “Unlocked Fractional N PLL” in this chapter.

b.Measure the input and output levels of the A15UlOO sampler. If the sampler appears defective, check the LO drive to the sampler as described in “Sampler and Sampler IF.”

c.Refer to steps 34 through 51 below.

Check First LO pretune frequency and amplitude (steps 9-12)

9.The pretuned frequency of the first LO must be sufficiently accurate for the YTO loop to acquire lock. The amplitude of the first LO must be sufficient to drive the A15UlOO sampler. Perform the YTO Adjustment procedure, particularly the YTO main coil adjustments. (If available, use a synthesized microwave spectrum analyzer instead of the microwave frequency counter specified in the adjustment procedure.)

10.If the YTO main coil cannot be adjusted, proceed to step 33 to troubleshoot the main coil coarse and fine DACs and main coil tune DAC.

11.The front-panel first LO OUTPUT should measure between t14.5 and t18.5 dBm in amplitude.

12.If the first LO OUTPUT amplitude is out of the specified range, perform the first LO distribution amplifier adjustment procedure. Refer to Chapter 2, “Adjustment Procedures.”

1 l-26 Synthesizer Section