ViewSonic VA902B Service Manual - Page 30
Output power is unstable
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UPC - 766907146318
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4. Output power is unstable Unstable power Check sampling Circuit Check the R pin voltage of IC803 about 2.5V Check pin1 of IC802 voltage is 5.8V Check R810, R811, R818 Check the C pin voltage of IC803 if 3V Change R810, R811, R818 Change IC803 Check R809, R808, R814, D809 Check D806, C815 if short Change D806, C815 Check pin3 of IC802 voltage about 1V ViewSonic Corporation Change R801, R805, R822, R823, R817 END 27 Confidential - Do Not Copy VA902/b
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4.
Output power is unstable
Unstable power
Check sampling
Circuit
Check R810,
R811, R818
Change R810, R811,
R818
Check the R pin
voltage of IC803
about 2.5V
Check R809, R808, R814,
D809
Check D806, C815 if
short
Change
D806, C815
Check pin1 of
IC802 voltage
is 5.8V
Check pin3 of
IC802 voltage
about 1V
Change R801, R805,
R822, R823, R817
END
Check the C pin
voltage of IC803
if 3V
Change
IC803
27
ViewSonic Corporation
Co
nfidential - Do Not Copy
VA902/b