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5.
Video is defective.
Turn up the screen control
and check whether the raster
appear.
0.7Vp-p
3Vp-p
50Vp-p
Heater: 6.3VDC
G1: -30V
G2: 500V _by high volt probe
ViewSonic Corporation
No video display
Does the entire screen
light up?
Yes
Are the input waveform
at P601 pin5, pin6, piin7
normal?
Yes
Are the waveform at the
pin118, pin19, pin20 of
IC601?
Yes
Are the waveform of the
terminal BK,RK,GK of
CRT socket normal?
Yes
Are the voltage on heater,
G1,G2 of CRT socket
normal?
Yes
The CRT is defective.
2
Confidential – Do Not Copy
No
The raster doesn't appear.
No
Check the signal cable or
computer
No H.blank or no power to IC
No
601 . Or pin 12 IC602 always
high
No
Video optput circuit defective
IC603 pin1, pin2, pin3
CRT drive circuit is defective
No
heater, power supply circuit
D206, G1, G2, FBT, D420,
Q420 and its drive circuit
E55-2
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