Wavetek 3000 Instruction Manual page 74

MAINTENANCE
Adj us t M30 FREQUENCY ADJUST trimmer (Fig-
ure 5-5) for minimum frequency indication
on counter ; then, carefully turn FRE-
QUENCY ADJUST trimmer clockwise until
counter indicates the frequency select-
ed by FREQUENCY switches . Disconnect
counter from RF OUT connector . A final
frequency check will be covered in
paragraph 5 .3 .11 .
5 .3 .5
PHASE-LOCKED LOOP #1 ADJUSTMENT
M31A
No adjustment of module M31A is necessary .
5 .3 .6
PHASE-LOCKED LOOP #2 ADJUSTMENT
M32A
See Figure 5-5 for location of M32A test
points and Figure 5-6
for adjustment
controls . Set frequency to 200 .000 MHz
and other
front-panel controls as
in
Section 5 .3 .4 . Connect digital
volt
meter to M32A pin 14, and
carefully ad-
just both
M30 -1 trimmers (A and B) to
produce a minimum reading on voltmeter .
This
voltage should be between +0 .5 V
and +3 .0 VDC . Set frequency
to.
239 .000
MHz,and note that
voltmeter reading is
still within above limits .
Set frequency to 200 .000 MHz and
con-
nect scope vertical
input (DC, 1 V/cm)
to M32A pin 15 .
Adjust M32A control (A)
for a 0 V scope
indication . Set Fre-
queney to 239 .000
MHz, and adjust M32A
control (B) to again produce a 0 V scope
indication .
5 .3 .7 Phase-Locked Loop #3 Adjustment
P .L .L . #3 consists of two modules : The
M33 and the M9 W . The test point is on
module M33 (Figure 5-5), while the ad-
justment controls are on module M9W
(Figure 5-6) . Set FREQUENCY to 250 MHz,
and
other front panel
controls as in
Section 5 .3 .4 . Connect scope vertical
input (DC, 1 V/cm) to M33 pin 5 . Adjust
M9W control (D) for a 0 V scope indica-
tion .
Set front-panel controls as follows :
MODE to FMx100, FREQ to 1 kHz and AM/FM
Vernier at maximum . Set scope vertical
input (on M33 pin 5) for AC, 50 mV/cm .
Adjust M9W control (C) for minimum (null)
indication of 1 kHz sine wave on scope .
Set FREQ to 400 Hz and note that
scope
presentation is a 400 Hz sine wave .
5 .3 .8 Phase-Locked Loop #4 Adjustment
Calibration of P .L .L . #4 involves three
modules : M172, M9W and
the M34 . Test
points are located on modules- M2M and
M34 (Figure 5-5), while adjustment con-
trols are located on
modules M172 and
M9W (Figures 5-4 and 5-6) .
Set FREQUENCY switches for 250 .000 MHz
and other front panel controls as in
Section 5 .3 .4 . Connect digital volt
meter to M172 pin °).;
then,
adj ust M172
250 MHz control (Figure 5-4) for a 0 .00
V reading on voltmeter . The voltmeter
may now be disconnected .
Connect frequency counter to RF OUT con-
nector and connect scope vertical input
(DC, 1 V/cm) to M34 pin 8 . Adjust M9W
control (A) for 0 V on scope . The count-
er should indicate a frequency of 250
MHz .
NOTE : Due to the way the M34 locks
on harmonics of 40 MHz, it is possible
to adjust M9W control
(A) for "0 V" at
multiples of 40 MHz offset from 250 MHz .
If this happens, it will be necessary to
readjust M9W control
(A) several turns
to
break lock and relock
at the next
multiple of
40 MHz until "0 V" can be
obtained with a 250 MHz counter reading .