Kenwood TM-631A User manual

144/220MHz FM DUAL BANDER KENWOOD
M631A Bryan WICR
SERVICE MANUAL BRron@bryan Fretds.net
©1989-8 PRINTED IN JAPAN
B51-8016-00(T)633
Knob
(K29-3111-04)x3
Microphone
(T91-0380-25)
Panel ass'y
(A20-7014-02)
Knob (SQ)
(K29-31 16-04)
Knob (AF)
Metallic cabinet (Top) (K29-3115-04]
(A01-1048-02)
Panel
(A20-7021-02}
Knob (MAIN)
(K29-3060-04)
Knob (SCAN, MUTE)
(K29-3112-04) x5 a
Knob (Up/Down)
(K29-3114-04)x2
(ey
Knob (Sub-Encoder) Knob (DUAL)
(K29-3145-04) (K29-3143-04) (K29-3113-04) x3
Knob (Button)
(K27-3026-04) x2 Knob (Low)
Knob (Button) (K29-3144-04)
(K27-3028-04) Metallic cabinet (Bottom)
(A01-1076-02)
CONTENTS
CIRCUIT DESCRIPTION 2CONTROL UNIT (X53-3250-12) 61
DESCRIPTION OF ELEMENTS 17 144 MHz TX-RX UNIT (X57-3400-1 2) 63
PARTS LIST 25 220 MHz TX-RX UNIT (X57-3410-10) 65
EXPLODED VIEW 46 FINAL UNIT (220 MHz) (X45-3350-10) 67
PACKING 48 FINAL UNIT (144 MHz) (X45-3350-10) 68
ADJUSTMENT 49 SCHEMATIC DIAGRAM 69
TERMINAL FUNCTIONS 56 LEVEL DIAGRAM 73
PC BOARD VIEW/SCHEMATIC DIAGRAM BLOCK DIAGRAM 75
144 MHz PLL UNIT (X58-3670-10) 59 TSU-6 (CTCSS UNIT) 76
220 MHz PLL UNIT (X58-3690-10) 60 SPECIFICATIONS Back cover
144/220MHz FM DUAL BANDER KENWOOD
M631A Bryan WICR
SERVICE MANUAL BRron@bryan Fretds.net
©1989-8 PRINTED IN JAPAN
B51-8016-00(T)633
Knob
(K29-3111-04)x3
Microphone
(T91-0380-25)
Panel ass'y
(A20-7014-02)
Knob (SQ)
(K29-31 16-04)
Knob (AF)
Metallic cabinet (Top) (K29-3115-04]
(A01-1048-02)
Panel
(A20-7021-02}
Knob (MAIN)
(K29-3060-04)
Knob (SCAN, MUTE)
(K29-3112-04) x5 a
Knob (Up/Down)
(K29-3114-04)x2
(ey
Knob (Sub-Encoder) Knob (DUAL)
(K29-3145-04) (K29-3143-04) (K29-3113-04) x3
Knob (Button)
(K27-3026-04) x2 Knob (Low)
Knob (Button) (K29-3144-04)
(K27-3028-04) Metallic cabinet (Bottom)
(A01-1076-02)
CONTENTS
CIRCUIT DESCRIPTION 2CONTROL UNIT (X53-3250-12) 61
DESCRIPTION OF ELEMENTS 17 144 MHz TX-RX UNIT (X57-3400-1 2) 63
PARTS LIST 25 220 MHz TX-RX UNIT (X57-3410-10) 65
EXPLODED VIEW 46 FINAL UNIT (220 MHz) (X45-3350-10) 67
PACKING 48 FINAL UNIT (144 MHz) (X45-3350-10) 68
ADJUSTMENT 49 SCHEMATIC DIAGRAM 69
TERMINAL FUNCTIONS 56 LEVEL DIAGRAM 73
PC BOARD VIEW/SCHEMATIC DIAGRAM BLOCK DIAGRAM 75
144 MHz PLL UNIT (X58-3670-10) 59 TSU-6 (CTCSS UNIT) 76
220 MHz PLL UNIT (X58-3690-10) 60 SPECIFICATIONS Back cover

Manual&Scan&
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and image quality, image quality will win. It’s 2021 and
storage and bandwidth is cheap.
This was captured on a Canon DR-G2140 scanner which is a
~7500 USD unit circa 2021. You may note some artifacts and
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about 250 USD if you’re feeling generous :-)
If you have a hard to find/out of print manual and would
like to make it available please reach out, I may be able
to scan and return it to you.
Thank you,
Bryan Fields, W9CR
[email protected]

TM-631A
CIRCUIT DESCRIPTION
Frequency Configuration The transmitted signal for both bands is generated direct os-
cillation and direct frequency division in the phaselocked oop.
The TM-631A uses asynthesized PLL and includes avariable
The signal is amplified by alinear amplifier before being ap-
frequency oscillator that enables selection of 5kHz, 10 kHz,
12.5 kHz, 20 kHz, or 25 kHz channel steps. (See Fig. 1.) plied for the antenna.
Signals received in the 144 MHz band are down-converted to
afirst intermediate frequency of 16.9 MHz by mixing with the
first local oscillator frequency (127.1 MHz to 131.095 MHz),
and then to the second intermediate frequency of 455 kHz by
mixing with the second local oscillator frequency of
17.355 MHz.
Signals received in the 220 MHz band are down-converted to
the first intermediate frequency of 30.825 MHz by mixing with
the first local oscillator frequency (189.175 MHz to
194.170 MHz), and then to the second intermediate frequen-
cy of 455 kHz by mixing with the second local oscillator fre-
quency of 30.37 MHz. Double conversion is thus used for both
the 144 MHz and 220 MHz bands.
Model T-631A
Unit
Final Unit X45-3350-10
Control Unit X$3-3250-12
220 MHz TX-RX Unit X57-3410-10
144 MHz TX-RX Unit X67-3400-12
Table 1Comparison of TM-631A
CFW455F
144~ 147.995 MHz
MCE
455kHz
Ist MIX 16.9 MHz
ANT SW RF AMP MIX,IF,DET
me
17.355 MHz
127.1~131.095 MHz sp
144 MHz STEREO
BAND PLL AF AMP 4]
PA TX AMP SYSTEM
ANALOGUE SW SPA JACK
144~147.995 MHz
MAIN
220~224.995 MHz ota MAIN/SUB
PA TX AMP 220 MHz
BAND PLL MIC AMP
SYSTEM
189.175 -194.170 MHz mic
220 ~224,995 MHz
MCF CFW455F
30.825 MHz 455kHz
ANT SW RF AMP +MIX, 1F,DET
Ist MIX
30.370 MHz
Fig. 11 Frequency Configuration
2
TM-631A
CIRCUIT DESCRIPTION
Frequency Configuration The transmitted signal for both bands is generated direct os-
cillation and direct frequency division in the phaselocked oop.
The TM-631A uses asynthesized PLL and includes avariable
The signal is amplified by alinear amplifier before being ap-
frequency oscillator that enables selection of 5kHz, 10 kHz,
12.5 kHz, 20 kHz, or 25 kHz channel steps. (See Fig. 1.) plied for the antenna.
Signals received in the 144 MHz band are down-converted to
afirst intermediate frequency of 16.9 MHz by mixing with the
first local oscillator frequency (127.1 MHz to 131.095 MHz),
and then to the second intermediate frequency of 455 kHz by
mixing with the second local oscillator frequency of
17.355 MHz.
Signals received in the 220 MHz band are down-converted to
the first intermediate frequency of 30.825 MHz by mixing with
the first local oscillator frequency (189.175 MHz to
194.170 MHz), and then to the second intermediate frequen-
cy of 455 kHz by mixing with the second local oscillator fre-
quency of 30.37 MHz. Double conversion is thus used for both
the 144 MHz and 220 MHz bands.
Model T-631A
Unit
Final Unit X45-3350-10
Control Unit X$3-3250-12
220 MHz TX-RX Unit X57-3410-10
144 MHz TX-RX Unit X67-3400-12
Table 1Comparison of TM-631A
CFW455F
144~ 147.995 MHz
MCE
455kHz
Ist MIX 16.9 MHz
ANT SW RF AMP MIX,IF,DET
me
17.355 MHz
127.1~131.095 MHz sp
144 MHz STEREO
BAND PLL AF AMP 4]
PA TX AMP SYSTEM
ANALOGUE SW SPA JACK
144~147.995 MHz
MAIN
220~224.995 MHz ota MAIN/SUB
PA TX AMP 220 MHz
BAND PLL MIC AMP
SYSTEM
189.175 -194.170 MHz mic
220 ~224,995 MHz
MCF CFW455F
30.825 MHz 455kHz
ANT SW RF AMP +MIX, 1F,DET
Ist MIX
30.370 MHz
Fig. 11 Frequency Configuration
2

TM-631A
CIRCUIT DESCRIPTION
Receiver Circuits
¢General
This set uses seperate receiver circuits for the 144 MHz and
220 MHz bands. These circuits extend from the antenna in-
put section to the IF detector.
©144 MHz
The incoming two meter band signal passes thru the trans-
mit/receive switching diode in the final unit. And then through
the antenna matching coil in the front unit. It is then amplified
by aGaAs FET radio-frequency amplifier, Filtered by athree-
stage bandpass filter that uses varicap tuning to reject unwant-
ed signal components, and is fed to the first mixer. There it
is mixed with the first local oscillator signal from the PLL to
generate the first IF signal (16.9 MHz). Spurious adjacent-
channel signals are removed in atwo-stage MCF (Monolithic
Crystal Filter).
The first IF signal is amplified and fed to the FM IF IC:MC3361D.
This IF signal is mixed with the second ocal oscillator frequency
of 17.355 MHz which results in asecond IF signal of 455 kHz.
Spurious adjacent-channel signals are removed from the se-
cond IF signal by ceramic filter. Then the signal is amplified
and detected to generate the audio signal.
Q!
RA2
16
02 G2
08
6
PLL OUT
Fig. 2144 MHz Front End (Varicap Tuning)
¢220 MHz band
The incoming 220 MHz signal passes thru the transmit/receive
antenna switching diodes in the final unit and then passes
through the antenna matching coil. It is then amplified by a
GaAs FET radio-frequency amplifier. Filtered by athree stage
bandpass filter that uses varicap tuning to reject unwanted sig-
nal components, and enters the first mixer, where it is mixed
with the first local oscillator signal from the PLL to generate
the first IF signal (30.825 MHz). Spurious adjacent-channel sig-
nals are removed by atwo-stage MCF.
The first IF signal is amplified and fed to the FM IF IC
(MC3361D). This IF signal is mixed with asecond ocal oscil-
lator frequency of 30.37 MHz which converts it to asecond
IF signal of 455 kHz.
Spurious adjacent-channel signals are removed from the se-
cond IF signal by an ceramic filter. The signal is then amplified
and detected to generate the audio signal.
Item Specification
Nominal center frequency 30.825 MHz
Pass bandwidth Max. +7.5 kHz at 3dB
Attenuation band width Max. +28 kHz at 40 dB
Ripple Max. 1.5 dB
Insertion loss Max. 3dB
Guaranteed attenuation 60 dB or greater at +1MHz;
40 dB or greater for spurious signal
Terminating impedance 1.4 kQ/1 pF
Table 2MCF (L71-0270-05) Characteristics
(220 MHz TX-RX Unit XF1)
Item Specification
Nominal center frequency 455 kHz+ 1kHz
6dB bandwidth Min. +6 kHz (above 455 kHz)
50 dB bandwidth Min. +12.5 kHz (above 455 kHz)
Ripple (455 +4 kHz) Max. 3dB
Insertion loss Max. 6dB
Guaranteed attenuation
Max. 35 dB
(455 +100 kHz)
Input-output matching 2.0 kQ
impedance
02
Table 3Ceramic Filter CFW455F (L72-0315-05)
Characteristics (220 MHz TX-RX Unit CF1,
144MHz TX-RX Unit CF1)
Item Rating
Nominal center frequen- 16.900 kHz
cy (fo)
3dB bandwidth +7.5 kHz or more
Attenuation bandwidth +25 kHz or less at 40 dB
+45 kHz or less at 60 dB
Guaranteed attenuation 70 dB or more within +1MHz
(Sprious response 40 dB or more)
80 dB or more within fo
-
(900~ 920 kHz)
Ripple 1.0 dB or less
Loss 1.5 dB or less
Input and output im-
1.8 kQ/O pF
pedance
Table 4MCF (L71-0279-05) Characteristics
(14 MHz TX-RX Unit XF1)
3
TM-631A
CIRCUIT DESCRIPTION
Receiver Circuits
¢General
This set uses seperate receiver circuits for the 144 MHz and
220 MHz bands. These circuits extend from the antenna in-
put section to the IF detector.
©144 MHz
The incoming two meter band signal passes thru the trans-
mit/receive switching diode in the final unit. And then through
the antenna matching coil in the front unit. It is then amplified
by aGaAs FET radio-frequency amplifier, Filtered by athree-
stage bandpass filter that uses varicap tuning to reject unwant-
ed signal components, and is fed to the first mixer. There it
is mixed with the first local oscillator signal from the PLL to
generate the first IF signal (16.9 MHz). Spurious adjacent-
channel signals are removed in atwo-stage MCF (Monolithic
Crystal Filter).
The first IF signal is amplified and fed to the FM IF IC:MC3361D.
This IF signal is mixed with the second ocal oscillator frequency
of 17.355 MHz which results in asecond IF signal of 455 kHz.
Spurious adjacent-channel signals are removed from the se-
cond IF signal by ceramic filter. Then the signal is amplified
and detected to generate the audio signal.
Q!
RA2
16
02 G2
08
6
PLL OUT
Fig. 2144 MHz Front End (Varicap Tuning)
¢220 MHz band
The incoming 220 MHz signal passes thru the transmit/receive
antenna switching diodes in the final unit and then passes
through the antenna matching coil. It is then amplified by a
GaAs FET radio-frequency amplifier. Filtered by athree stage
bandpass filter that uses varicap tuning to reject unwanted sig-
nal components, and enters the first mixer, where it is mixed
with the first local oscillator signal from the PLL to generate
the first IF signal (30.825 MHz). Spurious adjacent-channel sig-
nals are removed by atwo-stage MCF.
The first IF signal is amplified and fed to the FM IF IC
(MC3361D). This IF signal is mixed with asecond ocal oscil-
lator frequency of 30.37 MHz which converts it to asecond
IF signal of 455 kHz.
Spurious adjacent-channel signals are removed from the se-
cond IF signal by an ceramic filter. The signal is then amplified
and detected to generate the audio signal.
Item Specification
Nominal center frequency 30.825 MHz
Pass bandwidth Max. +7.5 kHz at 3dB
Attenuation band width Max. +28 kHz at 40 dB
Ripple Max. 1.5 dB
Insertion loss Max. 3dB
Guaranteed attenuation 60 dB or greater at +1MHz;
40 dB or greater for spurious signal
Terminating impedance 1.4 kQ/1 pF
Table 2MCF (L71-0270-05) Characteristics
(220 MHz TX-RX Unit XF1)
Item Specification
Nominal center frequency 455 kHz+ 1kHz
6dB bandwidth Min. +6 kHz (above 455 kHz)
50 dB bandwidth Min. +12.5 kHz (above 455 kHz)
Ripple (455 +4 kHz) Max. 3dB
Insertion loss Max. 6dB
Guaranteed attenuation
Max. 35 dB
(455 +100 kHz)
Input-output matching 2.0 kQ
impedance
02
Table 3Ceramic Filter CFW455F (L72-0315-05)
Characteristics (220 MHz TX-RX Unit CF1,
144MHz TX-RX Unit CF1)
Item Rating
Nominal center frequen- 16.900 kHz
cy (fo)
3dB bandwidth +7.5 kHz or more
Attenuation bandwidth +25 kHz or less at 40 dB
+45 kHz or less at 60 dB
Guaranteed attenuation 70 dB or more within +1MHz
(Sprious response 40 dB or more)
80 dB or more within fo
-
(900~ 920 kHz)
Ripple 1.0 dB or less
Loss 1.5 dB or less
Input and output im-
1.8 kQ/O pF
pedance
Table 4MCF (L71-0279-05) Characteristics
(14 MHz TX-RX Unit XF1)
3

TM-631A
CIRCUIT DESCRIPTION
Table 6MCF (L71-0228-05) Characteristics
(144 MHz TX-RX Unit XF1)
©AF Unit
The path from the detector output to the AF power amplifier
input consists of two separate identical circuits for the main
band and the subband. The audio signal is first switched by
an analog switch into the AF preamplifier for its corresponding
band. After amplification, the signal level is adjusted by atwo-
channel electronic volume control [C:M51523 which is con-
trolled by the MAIN VOLUME and BALANCE controls on the
front panel. An AF low-pass filter then removes unwanted high-
frequency components. Next the separate audio signals are
selected to speaker mixed or separate mode by analogue switch
circuit which is amplified by the STEREO audio power amplifi-
er before being applied the speaker. (See Fig. 3.)
@Preamplifier For main
IF detect @Squelch amplifier band
IF detect ©Preamplifier
@Squelch amplifier
Fig. 3AF Section
®Squelch Circuits
Independent squelch circuits are provided for the main band
and subband. These circuits receive the output from the de-
tector, remove the 50 kHz noise component, amplify the sig-
nal with two transistor stages, and rectify it by means of adiode
to generate the squelch control signal. After DC amplification,
the control signal is used to switch the main and sub pream-
plifiers on and off.
°SMeter Circuits
Independent Smeter circuits for the 144 MHz and 220 MHz
bands receive signals from the 455 kHz ceramic filter, amplify
if in two-stage meter amplifier, and rectify the resulting signal
to generate aDC voltage. The microprocessor converts the ana-
log DC voltage to adigital output that is used to drive an LCD
bar meter.
CFI 8c
DIO R39
IOK
Item Specification
Nominal center frequency
(fo)
10.7 MHz
Pass bandwidth Max. fo +7.5 kHz at 3dB
Attenuation bandwidth 1) Max. +25 kHz at 40 dB
2) Max. +45 kHz at 60 dB
Guaranteed attenuation 70 dB or more within +1 MHz
40 dB or more spurious
80 dB or more within -900 kHz to -920 kHz
Ripple Max. 1dB
Insertion loss Max. 1.5 dB
Terminating impedance 3kQ/0 pF
!
J
CPU
33pin
PTH01
t
ASS Y
©THI M2
c37 NOY C38:
ol
Q5 Le
P33.P30
Fig. 4144 MHz S-meter circuit
¢Switching of Balance Range
To disable the BALANCE control in the single mode, the con-
trol voltage range of the BALANCE control is switched. This
switching is done by aLow signal from the INH (Inhibit) pin
of the microprocessor that turns on transistor Q7 in the single
mode. Since the center voltage of the balance control resistor
is held to approximately 4V, the voltage at the BAL pin can-
not exceed 4V, so even if the balance VR is moved to the SUB
position, the main band remains unattenuated. (See Fig. 5and
6.)
In dual band mode In single band mode
Attenuation (dB)
144M LPF
For main band AF
PA
For sub band qn
220M
MN4066BS' M51523AL TC4053BF
AF
MAIN
SUB
MAIN
suB
os
AF
LPF
For sub
band
084
Voltage at BAL pin (V) Voltage at BAL pin (V)
Fig. 5Fig. 6
During normal operation, the two electronic volume controllers
in the set operate using the M51523AL, but when the remote
control unit (RC-10) is connected and used to adjust the out-
put level, they are controlled by the LC7532M.
When the remote control unit is connected, aHigh switch con-
trol signal is sent from the CE pin of shift register IC4 to force
the attenuation of the M51523AL to zero. (Normally the CE
output is Low.) The UP and DOWN signals from the shift
register then vary the attenuation of the LC7532M. (See Fig. 7.)
4
TM-631A
CIRCUIT DESCRIPTION
Table 6MCF (L71-0228-05) Characteristics
(144 MHz TX-RX Unit XF1)
©AF Unit
The path from the detector output to the AF power amplifier
input consists of two separate identical circuits for the main
band and the subband. The audio signal is first switched by
an analog switch into the AF preamplifier for its corresponding
band. After amplification, the signal level is adjusted by atwo-
channel electronic volume control [C:M51523 which is con-
trolled by the MAIN VOLUME and BALANCE controls on the
front panel. An AF low-pass filter then removes unwanted high-
frequency components. Next the separate audio signals are
selected to speaker mixed or separate mode by analogue switch
circuit which is amplified by the STEREO audio power amplifi-
er before being applied the speaker. (See Fig. 3.)
@Preamplifier For main
IF detect @Squelch amplifier band
IF detect ©Preamplifier
@Squelch amplifier
Fig. 3AF Section
®Squelch Circuits
Independent squelch circuits are provided for the main band
and subband. These circuits receive the output from the de-
tector, remove the 50 kHz noise component, amplify the sig-
nal with two transistor stages, and rectify it by means of adiode
to generate the squelch control signal. After DC amplification,
the control signal is used to switch the main and sub pream-
plifiers on and off.
°SMeter Circuits
Independent Smeter circuits for the 144 MHz and 220 MHz
bands receive signals from the 455 kHz ceramic filter, amplify
if in two-stage meter amplifier, and rectify the resulting signal
to generate aDC voltage. The microprocessor converts the ana-
log DC voltage to adigital output that is used to drive an LCD
bar meter.
CFI 8c
DIO R39
IOK
Item Specification
Nominal center frequency
(fo)
10.7 MHz
Pass bandwidth Max. fo +7.5 kHz at 3dB
Attenuation bandwidth 1) Max. +25 kHz at 40 dB
2) Max. +45 kHz at 60 dB
Guaranteed attenuation 70 dB or more within +1 MHz
40 dB or more spurious
80 dB or more within -900 kHz to -920 kHz
Ripple Max. 1dB
Insertion loss Max. 1.5 dB
Terminating impedance 3kQ/0 pF
!
J
CPU
33pin
PTH01
t
ASS Y
©THI M2
c37 NOY C38:
ol
Q5 Le
P33.P30
Fig. 4144 MHz S-meter circuit
¢Switching of Balance Range
To disable the BALANCE control in the single mode, the con-
trol voltage range of the BALANCE control is switched. This
switching is done by aLow signal from the INH (Inhibit) pin
of the microprocessor that turns on transistor Q7 in the single
mode. Since the center voltage of the balance control resistor
is held to approximately 4V, the voltage at the BAL pin can-
not exceed 4V, so even if the balance VR is moved to the SUB
position, the main band remains unattenuated. (See Fig. 5and
6.)
In dual band mode In single band mode
Attenuation (dB)
144M LPF
For main band AF
PA
For sub band qn
220M
MN4066BS' M51523AL TC4053BF
AF
MAIN
SUB
MAIN
suB
os
AF
LPF
For sub
band
084
Voltage at BAL pin (V) Voltage at BAL pin (V)
Fig. 5Fig. 6
During normal operation, the two electronic volume controllers
in the set operate using the M51523AL, but when the remote
control unit (RC-10) is connected and used to adjust the out-
put level, they are controlled by the LC7532M.
When the remote control unit is connected, aHigh switch con-
trol signal is sent from the CE pin of shift register IC4 to force
the attenuation of the M51523AL to zero. (Normally the CE
output is Low.) The UP and DOWN signals from the shift
register then vary the attenuation of the LC7532M. (See Fig. 7.)
4

TM-631A
CIRCUIT DESCRIPTION
Control Unit
|
TX-RX (220 MHz)
X53-3250-12 A/3 Unit X57-3410-10
|14 13 MAIN
AF ouT2
AV SE
4ow
Balance VR variable AF INI
range switching
13 C/3
(With RC-10 connected)
|! |High when remote control unit VR is ON
||Q5 Low when remote control unit VR is OFF
INH THY
|
|
=
|
up z£
a! ce Scs cs
High for dual band tos os
Low for single band 2
ES ES
6
1
Ic
a
o
PEF
_ - _
Remote controt elect VOL
I10
az TTT TTT TT
16
AMP AIS
IC2
TX-RX (144 MHz) unit 4
X57-3400-12
i8
AIM
Electronic VR switching IC1,2: TC4053BF
o=>
BAL 10 >
suB
2
8c
No
07 R22
560
Q4
ww
22
16 9
20
I82&4 1€5:LC7534mM
AF
POWER
Fig. 7AF Volume Switching Diagram
5
TM-631A
CIRCUIT DESCRIPTION
Control Unit TX-RX (220 MHz)
X53-3250-12 A/3 Unit X57-3410-10
14 13 MAIN
o=>
BAL 10 >
AV
Ou suB
Balance VR variable aAF INI
range switching
B/3 C/3
8c
(With RC-10 connected)
No
High when remote control unit VR is ON
Q5 Low when remote control unit VR is OFF
Q8 07 R22
560
Q4
ow
UP
High for dual band os
Low for single band
os
ES
16
1c
16
20
7
Remote controt elect VOL
10
8Z
AF
POWER
AMP AIS
TX-RX (144 MHz) unit 1c 2
X57-3400-12
AIM
Electronic VR switching IC1,2: TC4053BF
7AF Volume Switching Diagram
5

TM-631A
CIRCUIT DESCRIPTION
©Muting Circuit MAIN AF
There are three types of audio muting: 182 Mutes audio output dur-
MU1 :Mutes the main band momentarily during memory scan ing momentary memory
etc And durin on scan during transmission
gtransmission.
MU2 :Mutes the subband when the CTCSS key is pressed. sue
ar
AOM
MU3 :Operates when the MUTE key is pressed on the front 3pin 2as 2
AOS
panel. 9°
>
«iSHIFT
REGISTER
R45) [MAIN BAND
820 MUTE Ic3
iZpin
suB
as
R51 13 MU2
MUS
SUB BAND MUT
SUB BAND Active
20d8 MUTE High
Mutes subband
©Speaker selection wher CTCSS Microprocessor
Operates when MUTE is ON data
In the TM-631A, aselection between the separate and mix control is pressed
modes is made depending upon the connection between the on front panel
speaker output and the external speaker. (Refer to Table 5.) Fig. 8Mute Circuit
When the separate mode is engaged, an attenuator is insert-
ed for level adjustment. (Refer to Figure 8-1.)
Main AF signal +buzzer
R53t
Sub AF signal
=
TC40538F MAIN output to pin 1of IC4
only in separate mode
MSs MAIN/SUB output to pin 14 of IC4 in mix mode
3
MSS
SUB output in separate mode
Figure 8-1 Speaker separate circuit
When the speaker jacks are connected into the MAIN termi-
nal, the MSS terminal becomes open and the pins 10 and 11
of IC3 become ''H'' so that AF signals are each input to the
audio amplifier (IC4) at they stand separate. While when the
speaker jacks are not connected into the MAIN terminal, the
MSS terminal is grounded, the pins 10 and 11 of IC3 become
""L'' and R53 is shorted for level adjustment so that AF sig-
nals are mixed together into only the pin 13 of C4.
Connected to both
Without external Connected only
Connected only to
MAIN and
MAIN/SUB
AF speaker to MAIN terminal MAIN/SUB
terminal
terminals
signal
External speaker
Main Internal speaker External speaker External speaker connected to MAIN
terminal
External speaker
Sub Internal speaker Internal speaker External speaker connected to
MAIN/SUB terminal
Mix Separate Mix Separate
Table 6-1 Correspondence in connection between
speaker output and external speaker
6
TM-631A
CIRCUIT DESCRIPTION
©Muting Circuit MAIN AF
There are three types of audio muting: 182 Mutes audio output dur-
MU1 :Mutes the main band momentarily during memory scan ing momentary memory
etc And durin on scan during transmission
gtransmission.
MU2 :Mutes the subband when the CTCSS key is pressed. sue
ar
AOM
MU3 :Operates when the MUTE key is pressed on the front 3pin 2as 2
AOS
panel. 9°
>
«iSHIFT
REGISTER
R45) [MAIN BAND
820 MUTE Ic3
iZpin
suB
as
R51 13 MU2
MUS
SUB BAND MUT
SUB BAND Active
20d8 MUTE High
Mutes subband
©Speaker selection wher CTCSS Microprocessor
Operates when MUTE is ON data
In the TM-631A, aselection between the separate and mix control is pressed
modes is made depending upon the connection between the on front panel
speaker output and the external speaker. (Refer to Table 5.) Fig. 8Mute Circuit
When the separate mode is engaged, an attenuator is insert-
ed for level adjustment. (Refer to Figure 8-1.)
Main AF signal +buzzer
R53t
Sub AF signal
=
TC40538F MAIN output to pin 1of IC4
only in separate mode
MSs MAIN/SUB output to pin 14 of IC4 in mix mode
3
MSS
SUB output in separate mode
Figure 8-1 Speaker separate circuit
When the speaker jacks are connected into the MAIN termi-
nal, the MSS terminal becomes open and the pins 10 and 11
of IC3 become ''H'' so that AF signals are each input to the
audio amplifier (IC4) at they stand separate. While when the
speaker jacks are not connected into the MAIN terminal, the
MSS terminal is grounded, the pins 10 and 11 of IC3 become
""L'' and R53 is shorted for level adjustment so that AF sig-
nals are mixed together into only the pin 13 of C4.
Connected to both
Without external Connected only
Connected only to
MAIN and
MAIN/SUB
AF speaker to MAIN terminal MAIN/SUB
terminal
terminals
signal
External speaker
Main Internal speaker External speaker External speaker connected to MAIN
terminal
External speaker
Sub Internal speaker Internal speaker External speaker connected to
MAIN/SUB terminal
Mix Separate Mix Separate
Table 6-1 Correspondence in connection between
speaker output and external speaker
6

TM-631A
CIRCUIT DESCRIPTION
Transmitter Circuits
¢General
Except for the microphone amplifier and APC (Automatic Power
Control) circuits, the transmitting circuits are independent.
MIC AMP (X59-3610- 00)
_
_
*Modulation Circuit
The audio signal from the microphone is fed to three opera-
tional amplifiers which perform preemphasis, amplification, and
limiting, and form asplatter filter that removes unwanted high-
frequency components.
The modulation circuit directly modulates the VCO (Voltage
control oscillator) for the 144 MHz and 220 MHz bands by us-
ing avaricap. (See Fig. 9.)
RI6 0
W
C4. 27P
xR7 390K 0033 4
C3 R6 (272)
033 33K .033 82K 82K 82K a
+
|
x>x
+
;°
|
oeTo
Qi: 28c4ii6(y) ICl NuM45saM
144PLL
1
R5
ICs 2)
IN NC 8c
R85
MIC ClI7
220MD1 144 MHz TX-RX unit
Fig. 9Modulation Circuit
©Preamplifier Stage Circuit
Athree-stage linear amplifier is used in both the 144 MHz and
220 MHz bands. Due to its wideband design, this linear am-
plifier provides stable drive output without adjustment.
¢Power Amplifier Circuit
The drive signal is fed to the power modules and amplified to
the required levels. It then passes through the TX/RX switching
diode and afilter and is transmitted via the antenna.
Rating
Item Symbol Tc (°C) Unit Conditions
S-AV17 M57774
Operating voltage Vec 25 16 17
Current consumption lec 25 14 14
Input power Pin 25 Zo=ZL=500 0.6 0.6 (Vcci213.8 V)
Output power Po 25 Zo =ZL=500 65 55
Operating case tem- Tc (op) °c -30~+110 -30~+110
perature
°c -40~+110 -40~+110
Storage temperature Tstg
Table 5Maximum Ratings of Power Modules
¢APC and SWR (Standing Wave Retio) Protection Circuits
The APC (automatic transmit output control) circuit and pro-
tection circuit have independent detectors in both bands. The
control circuit is acommon hybrid IC.
The APC detects the output from the power module and feeds
the result to the hybrid IC. The SWR protection circuit extracts
aportion of the reflected wave generated by antenna mismat-
ching at the CM (Capacitance Matching) coupler, detects it,
and feeds the result to the hybrid IC.
The hybrid IC controls the power transistor 05 :2SD1406 (Y)
in the drive stage, controls the drive transistor and the second
pin of the power module, and thus varies the transmitter output.
7
TM-631A
CIRCUIT DESCRIPTION
Transmitter Circuits
¢General
Except for the microphone amplifier and APC (Automatic Power
Control) circuits, the transmitting circuits are independent.
MIC AMP (X59-3610- 00)
_
_
*Modulation Circuit
The audio signal from the microphone is fed to three opera-
tional amplifiers which perform preemphasis, amplification, and
limiting, and form asplatter filter that removes unwanted high-
frequency components.
The modulation circuit directly modulates the VCO (Voltage
control oscillator) for the 144 MHz and 220 MHz bands by us-
ing avaricap. (See Fig. 9.)
RI6 0
W
C4. 27P
xR7 390K 0033 4
C3 R6 (272)
033 33K .033 82K 82K 82K a
+
|
x>x
+
;°
|
oeTo
Qi: 28c4ii6(y) ICl NuM45saM
144PLL
1
R5
ICs 2)
IN NC 8c
R85
MIC ClI7
220MD1 144 MHz TX-RX unit
Fig. 9Modulation Circuit
©Preamplifier Stage Circuit
Athree-stage linear amplifier is used in both the 144 MHz and
220 MHz bands. Due to its wideband design, this linear am-
plifier provides stable drive output without adjustment.
¢Power Amplifier Circuit
The drive signal is fed to the power modules and amplified to
the required levels. It then passes through the TX/RX switching
diode and afilter and is transmitted via the antenna.
Rating
Item Symbol Tc (°C) Unit Conditions
S-AV17 M57774
Operating voltage Vec 25 16 17
Current consumption lec 25 14 14
Input power Pin 25 Zo=ZL=500 0.6 0.6 (Vcci213.8 V)
Output power Po 25 Zo =ZL=500 65 55
Operating case tem- Tc (op) °c -30~+110 -30~+110
perature
°c -40~+110 -40~+110
Storage temperature Tstg
Table 5Maximum Ratings of Power Modules
¢APC and SWR (Standing Wave Retio) Protection Circuits
The APC (automatic transmit output control) circuit and pro-
tection circuit have independent detectors in both bands. The
control circuit is acommon hybrid IC.
The APC detects the output from the power module and feeds
the result to the hybrid IC. The SWR protection circuit extracts
aportion of the reflected wave generated by antenna mismat-
ching at the CM (Capacitance Matching) coupler, detects it,
and feeds the result to the hybrid IC.
The hybrid IC controls the power transistor 05 :2SD1406 (Y)
in the drive stage, controls the drive transistor and the second
pin of the power module, and thus varies the transmitter output.
7

TM-631A
CIRCUIT DESCRIPTION
Power amplifier
144 MHz Final Unit
D2 c20 Ls Lio Ll ANT2
I44MHz
|
ANT
bo
FB
av eT
9
RF METER
PRO
CURR
POWER
LOW POWER
NN
Fts
220 MHz Final Unit
220 MHz TX-RX Unit
(X57-3410-10)
Ic
KCCOI fecal
Fig. 10 APC and SWR Protection Circuits
PLL Synthesizer
Fig. 11 is ablock diagram of the PLL and VCO sections of the
144 MHz and 220 MHz circuits. Afeature of the PLL system
in the TM-621 Ais that there are independent subunits for the
144 MHz and 220 MHz bands, each consisting of an upper
VCO section and alower PLL section. Both sections are en-
closed in asturdy case that shields them from external signals.
To provide 5kHz, 10 kHz, 12.5 kHz, 20 kHz, and 25 kHz
steps, the 12.8 MHz frequency of the reference oscillator in
both the 144 MHz and 220 MHz bands is divided by 2048 and
2056 according to the step count to yield frequencies of
6.25 kHz and 5kHz. Each VCO oscillates directly at the tar-
get frequency. After single-stage amplification, the frequency
is applied to apulse-swallow PLL IC which divides it, performs
phase comparison, and locks the frequency.
The PLL system for 144 MHz band has aconfiguration of two
independent VCO units for transmission and reception,
separately. For shorter lockup time of PLL, use of the output
of pin 10 (when transmitting: ''H'') in the PLL IC (M54969FP)
is made. Only the moment that transmission is entered, the
LPF stops function due to the switching operation of Q15
(Figure 13) to approach the transmission lock voltage to make
the lockup time of PLL shorter.
The PLL system for 220 MHz band performs locking without
TX/RX selection. Making use of the output of pin 10 (with TX:
"L') in the PLL IC (M54959FP), only the moment that TX is
engaged, the LPF stops function to approach the TX lock vol-
tage to make the lockup time of PLL shorter.
In the 144 MHz band, the relation ship between Fvco1 and the
division ratios is:
Fvcor =(144--16.9) ={(n1x128) +Al} xFosc +R
Fvco1 Output frequency of 144 MHz-band VCO
ni :Value to which binary 10-bit programmable counter
is set
Al :Value to which binary 7-bit programmable counter is
set
;
Fosc :Reference oscillator frequency, 12.8 MHz
R:Value to which binary 14-bit programmable counter
is set
R=2560 for 5kHz, 10 kHz, 20 kHz and 25 kHz
steps
R=2048 for 12.5 kHz steps
lf n1=198, A1=76, then with 5kHz, 10 kHz, 20 kHz and
25 kHz steps:
Fvco1 ={{198x128)+76}x12800 +2560
x5
=127100=127.1 MHz
76)
In the 220 MHz band the relation between Fvcoz (RX) and the
division ratios is:
Fyco2 =(220
-
30.825) ={(n2x 128)+A2} xFosc+R
Fvco2:Output frequency of 220 MHz-band VCO
Rand Fosc: Same step frequencies as in the 144 MHz band
In this case n2=295 and A2=75, so:
Fvco2 ={(295x128)+75}x12800 +2560
=(37760+75) x5
=189175=189.175 MHz
8

TM-631A
CIRCUIT DESCRIPTION
MDI
x87-3410-10,
iee LPF IF.CONT MODY VCO BUFF
|
AMP
{
21,02, DIO1,D102 DIO4 1
{
I
1ly LR/LT SW l
a
220 224.995 MHz
1
lee -7
PLL LPF F.CONT VCO BUFF yf) AMP
|osc
|
|Ms4osore 2SC3324(B) iT33c tt
QI02 I1
aw sw swrtt OTCII4EK
1|AMP (Y) Q105 (K52) os
MOD OTCII4EK
Txveo Buff tt ISV268
{
MHz X58-3670-10
127.1~131.095 MHz
X57-3400-12
MO(X59-3610-00)
Fig. 12 PLL and VCO Block Diagram
P/N Lock
X= IN
X-OUT 22 Test
Fin
VREF
PD
0swi
Swe
S| 24 Vec
l2 GND
CPS
M54959FP 28C3324(B) IT33C Isvi64 NJN a\tu23)
SW
a5 \ f Q3
DTC144 bed D8
EK J\EK
AMP
1SS268
2SC2714
(Y)
2SK582
esce7l4y 1DIO3,D1I04 LR/LT SW
2SK508 T2SC3I2O
2SC2714
x2
12.8
144~147.995 MHz
5
1
23
Ref. freq. divider Lock
osc 1/8 Div. det
Veco
2. Modulus V/A divider +4 Ref. freq. fR PD
prescalor {binary 7bitt select det
{1/128, 1/129)
VN Programmable divider fIN/N
(Binary 10 bit)
*2
"7
21 bit data latch
far
21 bit shift register
Latch signal
21pluse counter
i
IN
2
10
2
3
RST
Fig. 13 M54959 Pulse Swallow Control Circuit
9
TM-631A
CIRCUIT DESCRIPTION
MDI
x87-3410-10,
iee LPF IF.CONT MODY VCO BUFF
|
AMP
{
21,02, DIO1,D102 DIO4 1
{
I
1ly LR/LT SW l
a
220 224.995 MHz
1
lee -7
PLL LPF F.CONT VCO BUFF yf) AMP
|osc
|
|Ms4osore 2SC3324(B) iT33c tt
QI02 I1
aw sw swrtt OTCII4EK
1|AMP (Y) Q105 (K52) os
MOD OTCII4EK
Txveo Buff tt ISV268
{
MHz X58-3670-10
127.1~131.095 MHz
X57-3400-12
MO(X59-3610-00)
Fig. 12 PLL and VCO Block Diagram
P/N Lock
X= IN
X-OUT 22 Test
Fin
VREF
PD
0swi
Swe
S| 24 Vec
l2 GND
CPS
M54959FP 28C3324(B) IT33C Isvi64 NJN a\tu23)
SW
a5 \ f Q3
DTC144 bed D8
EK J\EK
AMP
1SS268
2SC2714
(Y)
2SK582
esce7l4y 1DIO3,D1I04 LR/LT SW
2SK508 T2SC3I2O
2SC2714
x2
12.8
144~147.995 MHz
5
1
23
Ref. freq. divider Lock
osc 1/8 Div. det
Veco
2. Modulus V/A divider +4 Ref. freq. fR PD
prescalor {binary 7bitt select det
{1/128, 1/129)
VN Programmable divider fIN/N
(Binary 10 bit)
*2
"7
21 bit data latch
far
21 bit shift register
Latch signal
21pluse counter
i
IN
2
10
2
3
RST
Fig. 13 M54959 Pulse Swallow Control Circuit
9