Kenwood TM-742 User manual

Kenwood 742/942 Service manual
!
I!hope!this!manual!is!of!use!to!you.!!Kenwood!has!not!made!this!available!as!a!PDF!
and!the!existing!scans!are!of!such!poor!quality!to!be!useless!for!any!serious!servicing!
use.!
!
Each! page! has! been! captured! at! 600! dpi! at! the! proper! page! size.! ! OCR! was!
performed!on!the!resulting!pages,!while!not!perfect!it!makes!for!easy!searching!in!
the!manual.!!I!inserted!the!bookmarks!and!the!additional!service!documents!at!the!
end.!
!
You!should!be!able!to!print!the!large!sheets!on!11x17!or!tile!them!on!8.5x11!paper!
if!needed.!
!
Please!do!not!charge!for!access!to!this!manual,!or!put!it!on!a!pay!walled!website.!!
Erik!this!means!keep!it!off!your!archive!of!plagiarized!content!known!as!mods.dk.!
!
Please!do!not!down!sample/change!the!resolution!of!this!manual!if!you!re-host!it.!!
I!maintain!the!master!copy!on!my!wiki!here:!!
http://wiki.w9cr.net/index.php/Kenwood_TM-742/642/942!!
!
I!paid!for!the!scanning!of!this!which!required!the!cutting!of!the!binding!of!my!service!
manuals.! ! I! cannot! say! enough! good! things! about! the! document! processing!
company!who!has!done!this!scan.!!If!you!need!a!manual!scanned!I!would!be!happy!
to!put!you!in!touch!with!Stefan!and!his!crew.!
!
Thank!you!and!73,!
!
Bryan!Fields,!W9CR!
[email protected]!
!
!

144/430 MHz, FM MULTI BANDER
TM-742 A/E
144/430/1200 m H z FM TRIBANDER
TM-942 A
SERVICE MANUAL
KEN OOD
©1992-12 PRINTED IN JAPAN
B51 -8192-00 (B) 1094
Panel Ass'y
(A62-0221-03):
TM-742A
(A62-0222-03): TM-742E
(A62-01 97-03): TM-942A
Mettalllc cabinet (T P) Knob (S Q L)
(A01-2068-03) (K29-4808-04)
ifaV I ilsD
sifinr
MiSi
Knob
(K29-4806-04)
Panel Ass'y
(A62-021 9-03)
Knob Ass'y (V L)
(K29-4840-04)
Knob
(K29-4805-04)
Photo is TM-942A
CONTENTS
»
I
OVER VIE ................................ 2
CIRCUIT DESCRIPTION ............................................ 3
DESCRIPTION OF COMPONENTS ........................ 51
SEMICONDUCTOR DATA ..................................... 68
PARTS LIST ............................................................ 71
EXPLODED VIE ................................................. 116
PACKING......... ................ .120
ADJUSTMENT . . ........................................ .122
PC BOARD VIE S/SCHEMATIC DIAGRAM
C NTR L UNIT (X53-346X-XX) ....................... 135
DISPLAY UNIT (X54-31 30-11) .........................137
SCHEMATIC DIAGRAM .................................... 139
1200M TX-RX UNIT (X57-3600-1 1) ................ 143
430/440M TX-RX UNIT (X57-359X-XX) .......... 149
220M TX-RX UNIT (X57-381 0-10) ............ 153
1 44M TX-RX UNIT (X57-3580-XX) ........ 157
50M TX-RX UNIT (X57-3800-01 ) ..................... 161
28M TX-RX UNIT (X57-3790-01 ). . . ............ 165
BLOCK DIAGRAM........................ 169
LEVEL DIAGRAM .................................................175
TSU-7 (CTCSS UNIT) . ..........................................177
MC-45 (MULTI FUNCTION MICROPHONE) ... 179
MC-45DM (MULTI FUNCTION MICROPHONE
ITH AUTOPATCH) ......... ................................... 180
UT-28S/50S/UT-220S/1200
SPECIFICATION ... 181
SPECIFICATION.................................. BACK COVER

TM-742 A/742 E/942A
OVERVIE
List of Destinations
Model Destination Destination
code
Model Destination Destination
code
TM-742A
North America
K
TM-942A
North America
K
TM-742A
Canada
P
TM-942A
Canada
P
TM-742E
Europe E
TM-942A
ther countries
M
TM-742E
Europe
E2
TM-742E
Europe
E3
TM-742A
ther countries
M
TM-742A
ther countries
M2
Units for Each Model and Destination
Unit Name
Parts. No.
TM-742A/E
TM-942A
Band Units
UT-28S UT-50S
UT-220S
UT-1200
K
p E
E2
E3
M
M2 K p M M (50)
M (50)
K (50)
M (10)
Control Unit
X53-3460-1 1
o o o o
Control Unit X53-3460-21
o o
Control Unit X53-3460-22
o
Control
Unit
X53-3462-71
o o
Control Unit
X53-3462-72
o
Display Unit
X54-31 30-11
o o o o
0
o o o o o
28TX-RX
X57-3790-01
o
50TX-RX
X57-3800-01
o
144TX-RX
X57-3580-1 1
o o o
144TX-RX
X57-3580-1 2
o o
o o o o o
220TX-RX
X57-3810-10
o
440TX-RX
X57-3590-1 2
oo
o
430TX-RX
X57-3590-22
o o
430TX-RX X57-3592-72
o o o o o
1 200TX-RX
X57-3600-1 1
o ooo
BAND UNITS
Any of the following optional band units may be installed
in the TM-742A/742E.
The same instructions,apply for the Tri-Bander as for the
Dual-bander.
OPTIONAL BAND UNIT
TM-742A
U.S.A. Version
UT-28S UT-50S UT-220S UT-1200
TM-742A
UT-28S UT-50S UT-1200
TM-742E
UT-28S UT-50S UT-1200
i
i

TM-742 A/742 E/942A
CIRCUIT DESCRIPTION
UT-28S
28 TX-RX Unit Frequency Configuration
The 28 MHz unit incorporates a variable frequency
oscillator
(VF ), based on a phase-locked-loop (PLL)
synthesizer system, that allows a channel step of 5,10,
15, 20, or 25 kHz to be selected. The frequency in the
receive signal channel is mixed with a first local oscillation
frequency of 36.83-38.525 MHz to produce a first
intermediate
frequency (IF) of 8.83 MHz.
This frequency is then mixed with a second local
oscillation frequency of 9.285 MHz to produce a second
IF of 455 kHz. This is called a double-conversion system.
The signal in the transmission channel is produced by
direct oscillation, is frequency-divided by a PLL circuit,
amplified by a linear amplifier, then transmitted.
28^29 695 MHz
36.83~38.525 MHz
,28~29.695MHz
MIC AMP
ANT
SW
MIX, IF, DET
Fig. 1 Frequency configuration
I
I
28 TX-RX Unit Receive Signal Channel
• Outline
The received signal from the antenna passes through
a low-pass filter in the final transmission stage and then
through a transmission/reception selection diode switch
to the receiving front end. The signal then passes
through an antenna matching coil and is amplified to high
frequencies
by a M S field-effect transistor. The un 
wanted components of the signal are eliminated by a
bandpass filter consisting of a three-stage variable ca 
pacitor. The resulting signal goes to the first mixer, is
mixed with the first local signal from the PLL circuit, then
converted to the first IF of 8.83 MHz. The unwanted
near-by signal components are then eliminated by a two-
Item
Rating
Center frequency
(fo)
8830 kHz
Pass bandwidth
± 6 kHz or more at 3 dB
Attenuation
bandwidth
± 20 kHz or less at 40 dB
±40 kHz or less at 60 dB
Guaranteed
attenuation
70 dB or more within Fo ±-1 MHz
(Spurious: 40 dB or more)
Ripple
1 dB or less
Insertion loss
2 dB or less
Terminating
impedance
4.7 kn//0pF
stage MCF.
The first IF signal is amplified and input to FM IF HIC
IC6 (KCD04). This signal is then mixed with the second
local oscillation frequency of 9.285 MHz to produce the
second IF signal of 455 kHz. The unwanted near-by
signal components are then eliminated by an FM ceramic
filter. The resulting signal is inputto IC6 again, amplified
to the second IF signal, and detected to produce an
audio signal.
• Signal-strength meter
The signal-strength meter output voltage of FM IF
HIC IC6 (KCD04) is supplied to the control unit.
Item
Rating
Nominal
center
frequency
455KHZ
6 dB bandwidth ± 6 kHz or more (from 455 kHz)
50 dB bandwidth
± 12.5 kHz or less (from 455 kHz)
Ripple (within.
± 5 kHz of 455 kHz
3 dB or less
Insertion loss (at
maximum output point) •
6 dB or less
Guaranteed attenuation
(within ± 100 kHz of 455
kHz)
35 dB or more
I/ matcing impedance
2.0kn
Table 1 MCF (L71-0422-05) (28TX-RX unit XF1)
Table 2 Ceramic filter CF M455F (L72-0372-05)
(28TX-RX unit CF1)

TM-742A/742 E/942A
CIRCUIT DESCRIPTION
• Shift-register circuit
The ES, CK, and DT serial data from the control unit
are sent to Cl (BU4094BF) to perform the control
operation outlined in the following table:
Pin No.
Name
Function
Pin No.
Name Function
Strobe
Enable input
Qs
Data Serial
data input
10
Q's
Clock Clock
input
11
Q8 TX/RX
selection. High when TX is set.
Q1
TX/RX selection. Low when TX is set
12
Q7
ATT switching: High when ATT is on
Q2 TX
power selection. Low when middle and low.
“ H ” when high.
13
Q6
High for AM; low for FM; High for narrow;
low for wide
Q3
TX power selection. Low when high and low.
“ H ” when middle.
14
Q5
High when off band
Q4
Low when off band
15 E
8V
Vss GND
16
VDD
8V
Table 3
ATT circuit
If there is cross modulation, the ATT circuit operates
to attenuate the received signal before it enters Q2 (FET
for high-frequency amplification).
28 TX-RX Unit Transmit Signal Channel
• Outline
In the transmission channel, the desired frequency is
produced by direct oscillation, and is directly frequency
modulated by means of a varicap diode.
• Modulator circuit
The audio signal from the control unit is input to
microphone
amplifier HIC ICS (KCA04). IC4 consists of
a preemphasis circuit, amplifier, limiter, and splatter
circuit that eliminates unwanted high-frequency
components. The voltage-controlled oscillator (VF )
signal is directly frequency modulated by means of a
varicap diode in the frequency modulator circuit.
• Younger-stage circuit
The signal output from the VC is input to drive
circuit HIC IC16 (KCB16). The amplifier can obtain a
stable drive output without adjustment because it has a
large bandwidth. An ARC circuit controls the collector
voltage in the Younger final stage.
• Power amplifier circuit
The drive signal is amplified to the specified level by
a discrete transistor. Q2 performs class B amplification,
and the collector output voltage is controlled by an ARC
circuit. Q202 amplifies the power by class C operation,
improving the efficiency of the final stage.
Z1 X58-3840- X
Q 202
L201
0201
I D17
Fig. 2 Power amplifier circuit
i
i