Display Unit; Encoder; Power Supply; Dimmer Function - Kenwood TK-790 Service Manual

TK-790/ ( B

8. Display Unit

The optional display unit (front panel unit) for the TK-
790(B)/H(B) comes in two models : KCH-10 and KCH-11
8-1. KCH-10 (Contain : TK-790)
This display unit consists of a CPU (IC4) containing the
LCD driver, a reset IC (IC2), 5V AVR (IC1), EEPROM (IC3),
and other components.

• Encoder

Channels are changed by the rotary encoder (ENC). The
up/down pulses from the rotary encoder enter the CPU
(IC4), and converted to a serial data signal, and are sent to
the control unit.

• Power supply

Power is supplied to the CPU by converting SB from the
control unit to 5V by IC1. And SB is supplied to the LED for
backlight.
30
) /H ( B )
CIRCUIT DESCRIPTION
LCD
PTT
ED1
IC4
HK
78064GCXXX8EU
D13
Microprocessor
RX
D17
TX
IC3
AT24C64N10SI27 EEPROM
SB
SW REF
SW SW SW SW SW SW SW
DM1 DM2 DM1 DM2 DM1 DM2
LCD BACK LAMP
KEY BACK LAMP
Fig. 12 KCH-10 block diagram
• CPU (containing LCD driver)
The on/off signals of keys other than the power switch,
and the PTT and HOOK signals, are converted to serial data
and sent to the control unit. Data is displayed on the 13-
segments, 8-digits LCD and 7-segments, 3-digits LCD by
the built-in LCD driver.

• Dimmer function

From the control of the CPU's DM1/DM2 port, you can
switch the LCD/KEY backlight, busy/TX LED, or the optional
KMC-28 key backlight as shown in the following table.
Dimmer LCD
setting
H H
M M
L L
OFF OFF
5V
AVR
D25 IC1
RST
NJM78L05UA
RST
IC2
RH5VL42C
S5 S6 S7
PF1 PF2 PF3
AF VR
S2 S3
ENCODER
KEY Busy/TX
ON ON
ON ON
ON ON
OFF OFF
SB
S1
POWER
PS
RST
S8 S9
PF4 PF5
MIC
1/2
TRD
RS1
RS2
INT SP
KMC-28
ON
ON
ON
OFF