Mitsubishi Electric LT-2220 Service Manual page 47

MODELS: LT-2220 / LT-2240 / LT-3020 / LT-3040 / LT-3050
2-4. No picture displayed and picture errors of VIDEO signal.
Enter an input of NTSC gray scale
in J2J0 connector, and select VIDEO1 (or 2) INPUT.
(Push the device UP button 3 times :
4 times in case of VIDEO2)
And then, perform AV reset by front switch.
The video level inputs about 1.0Vp-p.
Is all harness connected correctly?
(especially between PWB-MAIN
and LCD PANEL (J4A0-LCD))
YES
NO
Is OSD available?
YES
Is the digital video signal available at pin 14(G_7)
of IC4A1, and control signals of 3Vp-p available at
pins 27(HS : R4H6) and 28(VS : R4H5) and
31(CLK : R4H3) and 30(DE : R4H4) of IC4A1 ?
14 of IC4A1
(MSB of Green)
NO
Poor harness connection or
defective cable.
Problem is in IC300 or IC4A0 or IC4A1
(and peripheral circuits). Are the
specified voltages available at the
connectors below?
CN
Name
S5V J303
S3.3V J303
D3.3V J190
Psave1* J712
*control signal of D3.3V
YES
27 of IC4A1
(f=48KHz) H
28 of IC4A1
V
(f=60Hz)
31 of IC4A1
(f=70MHz)
30 of IC4A1
NO
Pin No. Voltage
12 5Vdc
13 3.3Vdc
7 3.3Vdc
5 3.3Vdc
3Vp-p
3Vp-p
3Vp-p
3Vp-p
YES
3Vp-p
1.0Vp-p
Problem is in the following
circuit (and peripheral
circuits) .
Voltage with PWB
problem including
the circuit
in problem
S5V SET(SUB)
S3.3V SET(SUB)
D3.3V SET(SUB)
Psave1 MAIN
IC300 or IC4A0 (and
peripheral circuits) are
out of order. (PWB-
MAIN)
LCD-module or IC4A1
(PWB-MAIN) are out of
order.