Agilent Technologies 856290216 service manual Troubleshooting an Unlocked YTO PLL

Troubleshooting an Unlocked YTO PLL

1.If the YTO PLL is unlocked, error code 301 should be displayed. Place the spectrum analyzer in ZERO SPAN. Figure 11-7 illustrates the simplified YTO PLL.

2.Move the jumper on A14J23 to connect pins 2 and 3 (TEST position). Refer to Figure 11-l for the location of A14J23. Error code 301 should no longer be displayed. (The YTO PLL feedback path is now open and the YTO error voltage is forced to zero.)

3.On the spectrum analyzer, press (CAL), MORE i OF 2, FREB DTBCBISE , and LO FREI) . The displayed LO FREQ is the desired YTO frequency calculated. Record the calculated frequency of the YTO below:

YTO Frequency (calculated) = MHz

4. Measure the YTO frequency at the front-panel First LO OUTPUT jack and record below:

YTO Frequency (measured) = MHz

--------------------------

1I		ASSEMBLY		I
r Al4 FREQUENCY CONTROL				1
			MAIN COIL	TUNING
TUNING DAC
	J17-2
				I	I
-		-

(9 TO 17

	I
U207	I	HP &58L$	HP	8563E
	I	sio		SW TCHIND
			A7
		OIST AMP ‘-Js - -‘LO		01 5T AW

I

J304			-10 TO +5 dEir
FRAC	N	TEST	60 TO	96 MHz
APPROX		-10 d&n	WHEN	LOCKED,SAME
60 TO		96 MHz	AS FRACTIONAL N FREQ

Figure 1 l-7. Troubleshooting an Unlocked YTO PLL

Synthesizer Section 1 l-25