联机上电有显示画面，但存在枕形失真

兴宁528

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<P class=MsoNormal><SPAN lang=EN-US><SPAN style="mso-spacerun: yes">&nbsp; </SPAN>分析：从故障现象看，故障出在枕形校正电路。</SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US><SPAN style="mso-spacerun: yes">&nbsp; </SPAN>处理：首先R701、VR702，但调整无效，检查VR701和VR702电位器本身正常，C701和C702两电容电压，Q701也正常。在排除外围电路故障的情况下，估计故障出在U701（LM358）上，在线测量U701芯片如下表：</SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US><SPAN style="mso-spacerun: yes">&nbsp; </SPAN>U701在线测量数据：</SPAN></P>
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<P class=MsoNormal>&nbsp;<SPAN lang=EN-US><?XML:NAMESPACE PREFIX = O /><O:P> </O:P></SPAN></P></TD>
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<P class=MsoNormal>故障值（<SPAN lang=EN-US>V）</SPAN></P></TD>
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<P class=MsoNormal>正常值（<SPAN lang=EN-US>V）</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>1</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>7.5</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>7.5</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>2</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>7.5</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>7.5</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>3</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>1.6</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>7.5</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>4</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>0</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>0</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>5</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>7.0</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>7.0</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>6</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>0</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>0</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>7</SPAN></P></TD>
<TD style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 155.25pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15.75pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" vAlign=top width=207>
<P class=MsoNormal><SPAN lang=EN-US>9.4</SPAN></P></TD>
<TD style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 152.25pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15.75pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" vAlign=top width=203>
<P class=MsoNormal><SPAN lang=EN-US>9.4</SPAN></P></TD></TR>
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<P class=MsoNormal><SPAN lang=EN-US>8</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>22</SPAN></P></TD>
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<P class=MsoNormal><SPAN lang=EN-US>22</SPAN></P></TD></TR></TBODY></TABLE>
<P class=MsoNormal><SPAN lang=EN-US><SPAN style="mso-spacerun: yes">&nbsp; </SPAN>从表中数据看，U<SUB>701</SUB>第3脚电压偏离正常值，更换U701后，联机上电，调用测试图显示画面，微调VR<SUB>701</SUB>、VR<SUB>702</SUB>，画面显示正常，故障排除。</SPAN></P>
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<P class=MsoNormal><SPAN lang=EN-US>&nbsp;<O:P> </O:P></SPAN></P>