No Raster (H.def Failure) - Tatung OMNISCAN SERIES Service Manual

6.4 NO RASTER (H.DEF FAILURE)
INPUT 64KHz
SYNC
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SIGNAL
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CHECK H. DEF.
OUTPUT PULSE
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NG
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CHECK VOLTAGE
SUPPLY CKT.
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OK
- - > COLLECTOR OF 0411
(800 - 1000Vp-p) (SEE ITEM 6.5)
-------> HV. CKT FAILURE
> 0611, R666, 0608, 0606
R479,D411
CHECK PWM-------------------------> PIN 2 OF T600
GENERATOR
S~UARE
WAVEFORM
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20Vp-p
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NO
~------------'-------------> R607, 0607,0608, 0606a
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0602, 0601, 0600, 0603, 0605
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YES 0605, C603, 0602, 0603
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CHECK FEEDBACK ----------------------> USING 16V VOLTAGE TO SIMULATE
CIRCUIT THE FEEDBACK VOLTAGE (ON PIN 3 OF 0620a)
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MEASURE THE WAVEFORM (PIN 2 OF T600)
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THE WAVEFORM WILL CHANGE WHEN
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16V (VIA 10 Kohm RESISTOR) TOUCH
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PIN 3 OF 0620a.
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NO
~ >
0620a, 0620b, R602, 0601
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YES
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CHECK HOR. DEF. - - - - - - - - - - - - - - - - - > H. DY, L402, L405, C428
CIRCUIT C429, C430
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CHECK DPC BOARD ----------------------> GROUNDING TRACK
PWB-1732 IF BREAK, THE PARABOLA SIGNAL
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WILL GET TO H1, H2 SIGNAL LINE
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VIA PINS 5, 6 OF P310
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THIS WILL CAUSE THE HOR. OSC
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UNSTABLE AND DAMAGE THE 0411.
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CHANGE A NEW
2SC4288A
AND POWER ON
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END
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6-4
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