Technical information

1716
3. A Missing Color
Is input signal
normal?
One color is
missing
CRT
Cathode (Rk, Gk, Bk)
is normal?
Is video
output IC802
waveform normal?
Each grid (G1, G2)
voltage normal?
Is the
output of pre-amp
(IC801,LM1238)
pin 19,20,21 all
normal?
Check video signal
cable or video card.
Trouble in IC801 or its
ambient circuit
Trouble in
video output
IC802
or ambient
Trouble in 80Vdc
line
Trouble in G1,G2 line
Replace CRT
No
No
No No
No
Yes
Yes
Yes
Yes
Yes
RK, GK, BK
About 40V p-p
0.7Vpp
2. No Raster
Trouble in
power supply
circuit
Trouble in power
supply circuit
Trouble in G1
line of main PWA
Trouble in FBT or its
pin4 ambient circuit
High Voltage
trouble in FBT
Trouble in 80Vdc
line of power
supply unit
Refer to trouble
in P.S.U
Refer to trouble in
PSU.
Is CRT
heater red-hot?
No
Yes
No
No
No
No
Yes
No
Yes
Yes
Yes
Yes
No
Is Heater
Voltage (CRT PWA)
about 6V?
Turn the Brightness
& Contrast control
to set Maximum
No Raster
Is whole
screen bright?
Check
G1 voltage about
-70V?
Is 80Vdc
line normal?
Does
the Brightness control
make screen
bright?
Is CRT
G2 (screen) voltage
about 480V?
Trouble in
CRT
Raster OK
Yes
Yes