东芝EUB-405型B超回波太弱故障检修

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                    <p><img data-type="gif" class="__bg_gif " data-ratio="0.10555555555555556" data-w="720" src="http://mmbiz.qpic.cn/mmbiz/M2H0aGBjWUTRia7nqkArYeKZUqEfdmpNibMPiaZk4gvlWk5v5lUKyXhjJP4CENKQeQt5HI8zwcTCWJOkicfWJiatdJQ/640?wx_fmt=gif" style="white-space: normal;letter-spacing: 0.544px;box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;width: auto !important;"  /></p><p><span style="font-size: 15px;">来源：医学工程在线</span><br  /></p><p><br  /></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span class="Apple-converted-space">&nbsp; &nbsp;&nbsp;</span><span style="font-size: 15px;">故障现象:日本东芝EUB-405型B超有字符显示，但无超声图像，将增益调到最大时，有微弱的回波显示且为负像。</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">&nbsp; &nbsp;&nbsp;</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">&nbsp; &nbsp; 分析与检修:B超的工作原理是超声回波信号由探头接收后，送到接收电路进行放大、聚焦、调相、对数放大、检波等处理，并输出模拟视频信号，然后由A/D转换器把模拟信号转换为数字信号，此数字信号经DSC电路进行数字转换后，再经D/A转换器转换成模拟的视频信号，显示出实时超声图像。</span><span style="font-size: 15px;">字符的产生由CPU控制，字符的数字信号在DSC电路中与数字超声图像信号混合后被D/A转换，把模拟视频信号送到监视器。</span><span style="font-size: 15px;">而超声波的发射、接收、数字扫描转换均由CPU统一控制。</span><span style="font-size: 15px;">因此，估计CPU和DSC等电路正常，问题可能出现在DSC以前的信号通道上，导致超声视频信号幅度太小。</span><span style="font-size: 15px;">一般的原因有以下三点：</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">(1)接收电路有故障，因增益下降，回波信号没能放大到足够大的幅度。</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">(2)超声波发射电路有故障，导致发射功率下降。</span><br style="word-wrap: break-word;"  /><span style="font-size: 15px;">(3)探头有故障.发射时表现为电一声转换率下降，接收时表现为声一电转换率下降。</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">&nbsp;&nbsp;&nbsp;</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">&nbsp; &nbsp; 根据以上分析，参照DSC电路原理简图(见图1)，首先测A/D人口，测得A/D转换器的输人端11脚的视频信号幅度约为0.4V，远小于正常值2V~3V，说明故障在A/D转换器之前。</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">&nbsp;&nbsp;&nbsp;&nbsp;</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">&nbsp; &nbsp; 参照主要信号通路图,依次测量IC2, IC3, IC4, IC5的输入和输出波形，发现只有IC3的输人和输出波形变化不大，且同相。</span><span style="font-size: 15px;">由图2得知负电位的超声回波信号从IC2的7, 8脚输出，经C56, C57. D8, D9, R71送到反相输入端2脚，再分两路送到IC4的2脚和IC5的2脚，IC3放大器的增益G= -R74/R71 =一12K?/1K?=–12，同时正输人端3脚经R73接地。</span><span style="font-size: 15px;">可见，此级是一个增益为12的反相放大器，而现在输人与输出端波形幅度相同，测得IC3的电源电压和外围元件均无异常，因此断定IC3 2525损坏，更换之.故障排除。</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">&nbsp;&nbsp;&nbsp;&nbsp;</span></p><p style="word-wrap: break-word;font-family: simsun;font-size: 16px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);line-height: 32px;"><span style="font-size: 15px;">小结:由于IC3损坏，无放大功能，但输入端的超声回波信号可通过负反馈电阻R74传输到6脚，造成输出假象，但幅度小，且同相，所以出现上述故障。</span></p><p><br  /></p><p><br  /></p><p style="white-space: normal;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;color: rgb(62, 62, 62);font-size: 16px;line-height: 25.6px;text-align: center;font-family: 微软雅黑;background-color: rgb(255, 255, 255);box-sizing: border-box 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62, 62);font-size: 12px;font-family: Arial, Verdana, sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;line-height: 24.381px;box-sizing: border-box !important;word-wrap: break-word !important;">公司官网：http://gb.parts-ultrasound.com/</span></p><p style="white-space: normal;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;color: rgb(62, 62, 62);font-size: 16px;font-family: 微软雅黑;line-height: 24.381px;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;line-height: 1.75em;text-indent: 0em;font-size: 14px;font-family: Arial, Verdana, sans-serif;box-sizing: border-box !important;word-wrap: break-word !important;">微信公众帐号：</span></p><p style="white-space: normal;text-align: left;"><img class="rich_pages" data-ratio="1" data-s="300,640" src="http://mmbiz.qpic.cn/mmbiz_png/dx3KibwtDhvcvQ5W66skZY3mYSqpoRYIMn3LOS0l9GkWVqSdiaw2RiclU8MiatfDmia3YvXxPRgDFiaZFibgUOEEfaYhA/640?wx_fmt=png" data-type="png" data-w="344"  /></p><p style="text-indent: 0em;white-space: normal;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;color: rgb(62, 62, 62);font-size: 12px;font-family: Arial, Verdana, sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">维修咨询：QQ: &nbsp;712638 404</span><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;"  /></p><p style="text-indent: 0em;white-space: normal;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;color: rgb(62, 62, 62);font-size: 12px;font-family: Arial, Verdana, sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">设备咨询: &nbsp; QQ: &nbsp;712638 405</span></p><p style="white-space: normal;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;color: rgb(62, 62, 62);font-size: 16px;font-family: 微软雅黑;line-height: 24.381px;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;font-family: Arial, Verdana, sans-serif;line-height: 1.75em;text-indent: 0em;box-sizing: border-box !important;word-wrap: break-word !important;">软件咨询：QQ: 712638 406</span><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;"  /></p><p style="text-indent: 0em;white-space: normal;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;color: rgb(62, 62, 62);font-size: 12px;font-family: Arial, Verdana, sans-serif;line-height: 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break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;">阿里店铺网址：</span><span style="max-width: 100%;">https://renchengyiliao.1688.com</span></span></p><p style="text-indent: 0em;white-space: normal;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;color: rgb(62, 62, 62);font-size: 12px;font-family: Arial, Verdana, sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">电子邮箱：sales@parts-ultrasound.com</span></p><p><br  /></p>