Kenwood TR-7400A Service Manual page 37

VRl
1
L5 L3 TPl
RX Unit
"
(1) Unlock circuit and its indicator.
A. When TPI of VCO unit (X50-1370-10) is grounded
with controls set arbitrarily.
(a) The unlock indicator on the panel should light.
(b) The RF voltage at TP2 of the RX unit (X55-
1150-10) should be attenuated by 20 dB or more.
B. When the MHz control is turned rapidly, the un-
lock indicator should go on and off.
(2) Frequency setting and its digital display circuit
When the MHz control is turned from 4 to 7, the
A.
frequency at terminal TP2 of the RX unit (X55-
1150-10) should vary in steps of 1 MHz.
B. When the 100 kHz control is turned from 0 to 9
with the MHz control set at 7, the frequency at
TP2 of the RX unit should vary in steps of 100 kHz.
C. When the 10 kHz control is turned from 0 to 9
with the 100 kHz control set at 9, the frequency
at TP2 of the RX unit should vary in steps of 10
kHz.
(3) Repeater circuit (f600 kHz TX shift) and its indi-
cator
Set the frequency as given below.
145.99
147.00
When the repeater switch is set at -600 or +600 and
at OFF (SIMP), frequency should be differ by 600
kHz only in the transmission mode.
2. ADJUSTMENT OF RX UNIT
2.1 Test Equipment Used
(1 DC power source
)
(2) Sweep generator
(3) Oscilloscope
(4) Jig for helical stage
(5) RF VTVM
(6) SSG
(7) AG
(8) AF VTVM
2.2 Helical Adjustment
(1) Ground TP2 and terminal LE of the VCO unit (X50-
1370-1 0).
(2) Connect the detector for helical adjustment to TPI
of the RX unit.
(3) Looking at the waveform appearing on the oscillo-
scope, make adjustment in the following way.
Adjust L1 and L2 (3 piston trimmers) alternately so
I
that the markers appear as shown Fig. 14.
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