ViewSonic VA902B Service Manual - Page 29
DC output voltage is unstable
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UPC - 766907146318
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3. DC output voltage is unstable Output Voltage Unstable Check Vbe of Q801 below 0.3V Check reference voltage Check circuit if short Check Q801, Q802 Check pinR of IC801 Check R810, R811 Check feedback circuit Check Vpin3-4 of IC801 about 6V END Check Vpin1-2 of IC801 about 1V Check R809, R814 Check ZD801, ZD802, ZD803, D803, D805 Check R809, R814, IC801, R818 Check C815, D806, R812 ViewSonic Corporation Confidential - Do Not Copy VA902/b 26
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3.
DC output voltage is unstable
Output Voltage Unstable
Check Vbe of
Q801 below
0.3V
Check circuit if
short
Check ZD801, ZD802,
ZD803, D803, D805
Check Q801, Q802
Check reference
voltage
Check pinR
of IC801
Check R809, R814,
IC801, R818
Check R810, R811
Check feedback
circuit
Check Vpin3-4 of
IC801 about 6V
Check Vpin1-2 of
IC801 about
1V
Check C815, D806,
R812
Check R809,
R814
END
26
ViewSonic Corporation
Co
nfidential - Do Not Copy
VA902/b