Circuit Description - Kenwood LZ-701W Service Manual

TEST MODE / CIRCUIT DESCRIPTION
Test Mode and Initialization
While holding the [SCRN] and [>] keys, reset (switch
on the power supply to)
the system to initialize it and enter the test mode.
(1) Initial condition
* Output source when the tuner is connected: TV mode
* Wide mode: Full [Full mode]
* Brightness: 31 (Max.) [Full mode]
* Tint/Color/Contrast/Black Level: 11 (Center) [Full mode]
* Dimmer: 31 (Max.) [Full mode]
* AV OUT switching: Normal
* FM-TX output: OFF
* Remote: ON
* Power ON/OFF: OFF
(2) Operations in test mode
• Power is ON.
• All of the screen adjustment items can be adjusted in
3 steps of Min., Center and Max. (Both Display and
DAC output)
• The value of the dimmer sensor input affects imme-
diately the output value.
• Other operations are identical to those in normal
modes.
• The communication with the tuner is held in the same
way as in normal modes. However, the Tint and Color
values are changed to the Center values by activating
communication after the EEPROM resetting. Their val-
ues can be adjusted in 3 steps (Min., Center, Max.).
• Storage in the EEPROM is not performed in any op-
eration in the test mode.
(3) Switching the power supply OFF in the test mode
turns the system into the shipment condition.

Circuit Description

1. Identification and switching
of tuner/hideaway box
The OSD microcomputer (IC101) communicates with
the tuner unit through the communication line (pins
15, 18, 20, 59, 60 and 65). When the communication
cannot be established, the microcomputer identifies
that the connected unit is the hideaway box.
• When the tuner is connected:
The input to IC206 is switched to the External RGB
position. Q007 is turned OFF to shut off the power
supply to the chroma block.
• When the hideaway box is connected:
The input to IC206 is switched to the Chroma RGB
position. Q007 is turned ON to supply the +5 V power
to the chroma block.
2. NTSC/PAL input identification
When the hideaway box is connected, the sync in the
input video signal is separated at IC204. The vertical
sync signal is input to the microcomputer (IC101: Pin
14), which identifies the NTSC or PAL format accord-
ing to the vertical sync frequency.
3. Chroma circuit
The chroma circuit functions only when the hideaway
box is connected. Chroma IC IC201 receives the com-
posite signal from pin 36 and sync separation signal
from pin 39, and converts the composite signal to RGB
signals, which are output at pins 23, 24 and 25.
4. LCD interface circuit
LCD Interface IC IC301 receives the video RGB sig-
nals from pins 6, 8 and 10, and receives the OSD RGB
signals from pins 13, 14 and 15. The IC converts the
input signals into the LCD RGB signals and outputs
them at pins 29, 32 and 35. This IC also performs the
gamma correction, RGB amplitude adjustment and
VCOM amplitude adjustment.
5. Screen adjustment
DAC IC IC105 varies the output voltage to assist the
screen adjustment.
Pin 1 varies the voltage at pin 41 of IC301 during the
black level adjustment.
Pin 2 varies the voltage at pin 5 of IC301 during the
contrast adjustment.
Pin 3 varies the output voltage at pin 21 of IC 201
during the TINT adjustment, which is possible when
the hideaway box is connected.
Pin 4 varies the output voltage at pin 20 of IC201 dur-
ing the color adjustment, which is possible when the
hideaway box is connected.
6. Power supply circuit
When power is supplied from the tuner unit or hide-
away box, IC001 is activated to supply power to the
OSD microcomputer (IC101). When power is
switched ON, IC101 activates the power supply cir-
cuitry. When Q001 goes ON, the main power is sup-
plied to the power supply circuitry. IC003 supplies
+5 V (for the chroma block and LCD module).
Q003 supplies +8 V (for the RGB SW).
Q005 supplies +7.5 V/+5 V (for the LCD interface cir-
cuit).
IC002 supplies +/-16 V (for the LCD module).
LZ-701W
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