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2. BPF (bandpass filter)
3.
(1)
(2)
(3)
Purpose:
To obtain a required bandwidth by adjusting the
bandpass filter.
Measuring instruments:
1)
Sweep generator
2)
Filter detector
3)
Oscilloscope
Adjusting procedures:
(Refer to Fig. 6)
1)
Disconnect
the wire to the TPi
and TP2
terminals on the printed circuit board of the
IF unit X48-0012-00.
2)
Connect
the sweep generator to the first grid
(pin 7) of GBAW8A in the unit X47-0005-00
through a capacitor of 0.01pF.
3)
Shift the band select switch to 28MHz.
4)
Detach the remote terminal of VFO.
5)
Insert a ceramic capacitor of 0.01nF (500WV)
between the earth and the cathode (pin 1) of
V3 in the unit X48-0012-00.
8)
After detaching the capacitor of 0.01uF and
filter detector, connect the TP1 and TP2 with
solder.
9}
Insert a connector into the remote terminal of
VFO.
Hump
shail be
less than 2dB
8.595MHz
—|___2d8
6GOO'KHz
morethan
Fig. 7
!FT and Crystal filter (Refer to Fig. 5)
(1) Purpose:
To adjust the IFT to 3.395MHz and, to shape the
wave form in the crystal filter.
(2)
(3)
(4)
Measuring instruments and tools:
1)
Sweep generator
2)
Filter detector
3)
After glow type oscilloscope
4)
Regulating rod
5)
Ceramic capacitor 0.014F/500WV
Adjusting procedures:
1)
Introduce the output
of approximately 0.1V
from the sweep generator to the first grid (pin
No. 1) of 6BBAG (V1) in the unit X48-0012-00
through a capacitor of O0.01nF.
2)
Connect the AGC terminal to GND.
3)
Connect the detector to the plate (pin No. 5)
of 6BA6 (V4)} located at the final stage of IF.
4)
Speed
up
the
sweeping
speed
to about
10
m-sec/em.
Adjust T3 and T4 while displaying
the characteristic of IF stage on the oscillo-
scope.
In this case, T4 must be adjusted by
moving the upper and lower cores since it is
an !FT for detection.
5)
At this stage, slower the sweeping speed up to
about 0.5 sec/cm and obtain such wave-form
as shown
in Fig. 8 by adjusting T1 and T2,
while plotting the wave-form of crystal filter
on the oscilloscope.
6)
Minimize the ripple components by adjusting
the
3.4MHz
trap
in T5
(white).
If the
wave-form
is not
nearly affected
by T5 the
core must be placed at the innermost position.
7)
Disconnect
the capacitor of 0.0iuF
and the
detector and remove the AGC from GND.
8)
While keeping watch
on the S meter, retune
the T3 to obtain a maximum of the S meter.
Adjustment without slow sweeping
When
the slow-sweeping
can not be used, adjust-
ment must be made as follows.
1}
Receive an appropriate signal (SSG or marker
produced
inside the set) at nearly
the center
portion in the characteristic of filter detector.
2)
Adjust every IFT so that the deviation of the
S meter becomes maximum.
3)
Fine adjustment for T3 and T4 nust be made
by moving slightly the main turing
knob to
the left or the right in order to mimimize (the
deviation of S meter must be minimized) the
ripple components of filter.
4)
At this stage, perform adjustmentdescribed in
Item 6), paragraph (3).
23
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