Nokia 447ZiPlus - No Raster Display Troubleshooting

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(3) No Raster appear
Is the
voltage at O/P
of D442 normal
(69…165V)?
Is
the H.V.
correct
?
Does raster
light up with
SCREEN control
turned clockwise
?
Is the
voltage at
heater normal
(6.3V) ?
Is the
waveform at
Pin 1 of T430
normal ?
Is the
waveforms at
Pin 26 of I401
normal ?
Is the
voltage at
cathode of
D453 normal ?
Are
Q433,
D434 OK ?
Is the
high voltage
protection CKT
active ?
No raster appear
Check B+ converter
CKTQ440, Q438,
Q
439
,
D442
Open L440, Input 31KHz
signal apply 80V DC on
Pin 9 of T440
Replace the
defective
Reset SCREEN
control.
Check brightness
circuit Q495,
Q497, R482
Check spot killer
Ckt Q348, D348
Check FBT, CRT
Check R930, P902
Check I401
Check Q429,
D428, C427, R424
+14V to Q429
–9V to Q429
Check D446, D449
R447, R445, C434,
C435, C451, P440,
L483
Check T440, P440,
T430, CRT
N
o
N
o
N
o
N
o
N
o
N
o
N
o
N
o
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
N
o