刚做好的DAC如同晴天霹雳,特上来请教J版![求助]

Julien

连线我就说不清楚了，还是仔细检查下吧

同轴输入变压器是隔离应用？最好找这个DAC的资料看一下

Yifei1406

接下去任务就是检查错误了,首先想问个问题,同轴信号线进来是象我图上画的接吗?还有C48不接可以吗?原图是光纤输入处,我不用光纤输入,就把该部分去掉了<img src="attachments/dvbbs/2005-6/2005623162616178.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-6/2005623162616178.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />

Julien

一是前级信号线屏蔽不良，在没有接地的情况下引入了噪音
二是前级是一点接地，和DAC接地回路形成了地线环路

Yifei1406

步行者

接地不良

Yifei1406

灯丝一端接100V与灯丝两端接平衡电阻中心接地效果是一样的吗?

Julien

噪音还有可能是电位器引入的，如果是其他原因查找起来就比较麻烦

Yifei1406

<img src="attachments/dvbbs/2005-6/2005630174525669.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-6/2005630174525669.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />

Yifei1406

是解码器的输入信号线的屏蔽不良造成的还是前极输入信号线的屏蔽不良造成的?我都用了屏蔽线了呀!唯有DAC胆部分的输入偶合电容到栅极的一小段没用屏蔽线,但只有4CM长!

Julien

Yifei1406

我最后灯丝用四极RC滤波，现在灯丝交流声只有耳朵贴着喇叭才能听到，但是把我的前极电位器开到12点钟有明显的交流声，往左右旋转几乎没有交流声，这是什么道理？现在DAC胆输出部分我没有接平衡电阻

Julien

Yifei1406

<img src="attachments/dvbbs/2005-6/200562810572281.gif" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-6/200562810572281.gif\');}" onmousewheel="return imgzoom(this);" alt="" />

Yifei1406

Julien

反之则向灯丝发射，但是向灯丝发射不会干扰阴极

Yifei1406

我想用LM317做稳压

Julien

Yifei1406

<img src="attachments/dvbbs/2005-6/200562718132473.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-6/200562718132473.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />

Yifei1406

Julien

比如用两电阻分压得到，当然要给接地的电阻并联一个电容，保证交流是0电位
然后把原来灯丝接地的那端接在100V电位这一点，另一端悬空