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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
r
--------------------------
Al4
FREQUENCY
CONTROL
ASSEMBLY
1
I
1
I
MAIN
COIL
TUNING
TUNING
DAC
J17-2
-
-
I
I
(9
TO 17
U207
I
I
I
sio
HP
&58L$
HP
8563E
A7
SW
TCHIND
I
OIST
AMP
‘-Js
-
-‘LO
01
5
T
AW
J304
FRAC
N
TEST
APPROX
-10
d&n
60
TO
96
MHz
-10
TO
+5
dEir
60
TO
96
MHz
WHEN
LOCKED,SAME
AS
FRACTIONAL
N
FREQ
Figure 1
l-7.
Troubleshooting an Unlocked YTO PLL
Synthesizer Section
1 l-25