Power Supply - Kenwood TK-3310 Service Manual

5-4. Key Input
Keys and channel selector circuit.
The signal from the keys and channel selector are direct-
ly input to the MCU, as shown in Figure 10.
IC820
MCU
S
A
B
C
Fig. 10 Key input
6. Signaling Circuit
6-1. Encode
■ Low-speed data (QT, DQT)
Low-speed data is output from pin 2 of the MCU. The sig-
nal passes through the low pass CR fi lter, and goes to the
baseband IC (IC812). The signal is mixed with the audio sig-
nal and goes to the VCO and TCXO (X1) modulation input
after passing through the D/A converter inside the baseband
IC (IC812) for BAL adjustment.
IC820
MCU
2
LSDO
3
HSDENC
Fig. 11 Encode
CIRCUIT DESCRIPTION
Selector
Side2
Side1 PTT
IC812
Baseband IC
18 24
VCO
ALT MOD2
21 23
TCXO
MIC MOD1
■ High-speed data (2-tone)
High-speed data (HSD) is output from pin 3 of the MCU.
HSD deviation made by an adjustment in the MCU is passed
through the low pass CR fi lter and then applied to the base-
band (IC812).
The signal is mixed with the audio signal and goes to the
VCO and TCXO.
■ MSK/DTMF
The MSK/DTMF signal is generated in the baseband IC
(IC812). The signal passes through the D/A converter (inside
the audio processor: IC812) and is routed to the VCO. When
encoding the MSK/DTMF, the microphone input signal is
muted.
6-2. Decode
■ QT/DQT
The output signal from the IF IC (IC401) enters the MCU
(IC820) through IC812. IC820 determines whether or not
the QT or DQT matches the preset value, and controls the
AFSW and speaker output sounds according to the squelch
results.
■ 2-tone
Part of the received AF signal output from the IF IC (IC401)
passes through the baseband IC (IC812) goes to the other
AF amplifi er IC808, is compared, and then goes to IC820.
IC820 checks whether or not the 2-tone data is necessary. If
it matches, IC820 carries out a specifi ed operation, such as
turning the speaker on.
■ MSK (FleetSync)
The MSK input signal from the IF IC (IC401) goes to
IC812. The decoded information is then processed by the
MCU.
■ DTMF
The DTMF input signal from the IF IC (IC401) goes to
IC812. The decoded information is then processed by the
MCU.

7. Power Supply

There are fi ve 5V power supplies and three 3.3V power
supplies: 50M, 50V, 50C, 50R, 50T, 33M, 33MS and 33B.
50M and 33M are always output while the power is on.
33MS is always output, but turns off when the power is
turned off, to prevent malfunction of the MCU.
50C is a common 5V and is output when SAVE is not set
to ON.
50R is 5V for reception and output during reception.
50T is 5V for transmission and output during transmis-
sion.
50V is 5V for the SP/MIC connector.
33B is 3.3V for the baseband IC (IC812).
TK-3310
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