本文將對開關(guan)電源中恒電流源電路的工作原理及特點等進(jin)行分(fen)析(xi)，供讀者。

　　一、開關電源恒流源電路的(de)(de)(de)(de)(de)構(gou)成(cheng)及工作(zuo)(zuo)原(yuan)理由(you)(you)分立(li)(li)元件(jian)組成(cheng)的(de)(de)(de)(de)(de)開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)中(zhong)的(de)(de)(de)(de)(de)恒(heng)流(liu)源(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)路(lu)由(you)(you)分立(li)(li)元件(jian)組成(cheng)的(de)(de)(de)(de)(de)開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)采用恒(heng)流(liu)源(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)路(lu)的(de)(de)(de)(de)(de)彩(cai)電(dian)(dian)(dian)(dian)(dian)有：長(chang)虹NC-2、NC- 3、A6等機(ji)心系(xi)列闈電(dian)(dian)(dian)(dian)(dian)。另(ling)外，東芝2929DH/DXH彩(cai)3開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)基(ji)(ji)(ji)(ji)本相(xiang)同(tong)，也是(shi)采用恒(heng)流(liu)源(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)揠。，是(shi)這種開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)中(zhong)的(de)(de)(de)(de)(de)振蕩(dang)和(he)恒(heng)流(liu)源(yuan)(yuan)(yuan)(yuan)原(yuan)理圖(tu)。振蕩(dang)‘路(lu)由(you)(you)-⑨繞組是(shi)振蕩(dang)電(dian)(dian)(dian)(dian)(dian)路(lu)的(de)(de)(de)(de)(de)反饋支路(lu)。恒(heng)流(liu)源(yuan)(yuan)(yuan)(yuan)由(you)(you)VQ820、R822、VD820、C821、R823、T803⑦~⑧和(he)⑦⑨繞組構(gou)成(cheng)。其工作(zuo)(zuo)原(yuan)理是(shi)：在(zai)VQ83截止期間，T803的(de)(de)(de)(de)(de)⑧端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)為(wei)正(zheng)，⑨端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)為(wei)負(fu)(fu)。⑨端(duan)的(de)(de)(de)(de)(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)經(jing)R823加(jia)到VQ820的(de)(de)(de)(de)(de)基(ji)(ji)(ji)(ji)極，使(shi)VQ820截止。T803⑧端(duan)的(de)(de)(de)(de)(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)通(tong)過VD820向(xiang)C821充(chong)電(dian)(dian)(dian)(dian)(dian)，C821上(shang)充(chong)得的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)就成(cheng)為(wei)VQ820導通(tong)時所需(xu)的(de)(de)(de)(de)(de)工作(zuo)(zuo)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。VQ83導通(tong)時，T803⑧端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)變負(fu)(fu)，⑨端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)由(you)(you)負(fu)(fu)變正(zheng)。⑧端(duan)的(de)(de)(de)(de)(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)加(jia)到VD820正(zheng)極使(shi)其截止，⑨端(duan)的(de)(de)(de)(de)(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)經(jing)R823加(jia)到VQ820基(ji)(ji)(ji)(ji)極使(shi)其導通(tong)。VQ820導通(tong)后，流(liu)經(jing)VQ820集-射之間的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)便成(cheng)為(wei)VQ83的(de)(de)(de)(de)(de)基(ji)(ji)(ji)(ji)極注(zhu)人電(dian)(dian)(dian)(dian)(dian)流(liu)。VQ820的(de)(de)(de)(de)(de)導通(tong)電(dian)(dian)(dian)(dian)(dian)流(liu)不受交流(liu)輸(shu)人電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)波動(dong)的(de)(de)(de)(de)(de)影(ying)響，其大小取決于C821上(shang)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)和(he)電(dian)(dian)(dian)(dian)(dian)阻R822的(de)(de)(de)(de)(de)大小，所以，VQ83的(de)(de)(de)(de)(de)基(ji)(ji)(ji)(ji)極電(dian)(dian)(dian)(dian)(dian)流(liu)同(tong)樣不受交流(liu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)波動(dong)的(de)(de)(de)(de)(de)影(ying)響，這就展寬(kuan)了開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)對交流(liu)輸(shu)入電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)(de)(de)(de)適(shi)應(ying)范圍。

　　恒流(liu)源(yuan)電(dian)(dian)路(lu)(lu)6333等。采用(yong)STR-S6309組(zu)成開關電(dian)(dian)源(yuan)的彩電(dian)(dian)有：康佳06系列），夏普25N42-E2、29FN1、29AW1及寬屏W288、W328，熊貓C64P2、2919，長城(cheng)G8173MF、G8263、G8363，創維CTV-8259、CTV-8298.厚膜電(dian)(dian)路(lu)(lu)STR-S6308與STR-S6309內部電(dian)(dian)路(lu)(lu)結構(gou)基本(ben)相(xiang)同，恒流(liu)源(yuan)電(dian)(dian)路(lu)(lu)和原理完全相(xiang)同。下面(mian)以STR-S6308厚膜電(dian)(dian)路(lu)(lu)組(zu)成的開關電(dian)(dian)源(yuan)為例說(shuo)明其恒流(liu)源(yuan)工(gong)作原理。

　　是(shi)STR-6308厚膜電(dian)路(lu)(lu)組(zu)成(cheng)的(de)(de)(de)(de)(de)開(kai)關電(dian)源中的(de)(de)(de)(de)(de)振(zhen)蕩(dang)和(he)恒(heng)流(liu)(liu)(liu)電(dian)路(lu)(lu)原(yuan)理圖。圖中，IC801內部(bu)(bu)的(de)(de)(de)(de)(de)Q1是(shi)開(kai)關管(guan)，R803、R804是(shi)振(zhen)蕩(dang)啟動(dong)電(dian)阻(zu)，C812、R807、T803①-②繞組(zu)是(shi)振(zhen)蕩(dang)電(dian)路(lu)(lu)的(de)(de)(de)(de)(de)反饋支路(lu)(lu)。恒(heng)流(liu)(liu)(liu)源電(dian)路(lu)(lu)由(you)IC801內部(bu)(bu)的(de)(de)(de)(de)(de)Q3、R2、R3、D2及外部(bu)(bu)的(de)(de)(de)(de)(de)C814、D803、R806和(he)T803①-②繞組(zu)構成(cheng)。其(qi)(qi)恒(heng)流(liu)(liu)(liu)源工作原(yuan)理為(wei)(wei)(wei)(wei)：在（1截(jie)止期間(jian)，T803②端電(dian)壓(ya)(ya)(ya)(ya)(ya)為(wei)(wei)(wei)(wei)正，①端電(dian)壓(ya)(ya)(ya)(ya)(ya)為(wei)(wei)(wei)(wei)負(fu)。T803②端電(dian)壓(ya)(ya)(ya)(ya)(ya)通(tong)(tong)(tong)過IC801內部(bu)(bu)的(de)(de)(de)(de)(de)D2向(xiang)C814充電(dian)，其(qi)(qi)充電(dian)電(dian)流(liu)(liu)(liu)路(lu)(lu)徑(jing)為(wei)(wei)(wei)(wei)：T803②④一814-803-803①。C814上充得的(de)(de)(de)(de)(de)電(dian)壓(ya)(ya)(ya)(ya)(ya)就成(cheng)為(wei)(wei)(wei)(wei)Q3導(dao)(dao)通(tong)(tong)(tong)時所(suo)需要的(de)(de)(de)(de)(de)工作電(dian)壓(ya)(ya)(ya)(ya)(ya)。在Q1導(dao)(dao)通(tong)(tong)(tong)時，T803②端電(dian)壓(ya)(ya)(ya)(ya)(ya)由(you)正變(bian)負(fu)，①端電(dian)壓(ya)(ya)(ya)(ya)(ya)由(you)負(fu)變(bian)正。②端的(de)(de)(de)(de)(de)負(fu)電(dian)壓(ya)(ya)(ya)(ya)(ya)加(jia)到(dao)D2的(de)(de)(de)(de)(de)正極(ji)(ji)使其(qi)(qi)截(jie)止，①端的(de)(de)(de)(de)(de)正電(dian)壓(ya)(ya)(ya)(ya)(ya)加(jia)到(dao)IC801的(de)(de)(de)(de)(de)⑤腳，再通(tong)(tong)(tong)過其(qi)(qi)內部(bu)(bu)R3加(jia)到(dao)Q3的(de)(de)(de)(de)(de)基極(ji)(ji)使其(qi)(qi)導(dao)(dao)通(tong)(tong)(tong)。Q3導(dao)(dao)通(tong)(tong)(tong)后，C814通(tong)(tong)(tong)過Q3放(fang)電(dian)，其(qi)(qi)放(fang)電(dian)電(dian)流(liu)(liu)(liu)路(lu)(lu)徑(jing)為(wei)(wei)(wei)(wei)：C814正極(ji)(ji)->IC801dH3ce極(ji)(ji)->Qlbe極(ji)(ji)―IC801②―R806->C814負(fu)極(ji)(ji)。Q3導(dao)(dao)通(tong)(tong)(tong)后，流(liu)(liu)(liu)過Q3集(ji)射之間(jian)的(de)(de)(de)(de)(de)電(dian)流(liu)(liu)(liu)便(bian)成(cheng)為(wei)(wei)(wei)(wei)（1的(de)(de)(de)(de)(de)基極(ji)(ji)注人(ren)(ren)電(dian)流(liu)(liu)(liu)。因為(wei)(wei)(wei)(wei)Q3的(de)(de)(de)(de)(de)導(dao)(dao)通(tong)(tong)(tong)電(dian)流(liu)(liu)(liu)不受(shou)交(jiao)流(liu)(liu)(liu)輸人(ren)(ren)電(dian)壓(ya)(ya)(ya)(ya)(ya)波動(dong)的(de)(de)(de)(de)(de)影(ying)(ying)響，只(zhi)取決(jue)于(yu)C814上的(de)(de)(de)(de)(de)電(dian)壓(ya)(ya)(ya)(ya)(ya)和(he)電(dian)阻(zu)R806的(de)(de)(de)(de)(de)電(dian)阻(zu)大小，所(suo)以，開(kai)關管(guan)Q1的(de)(de)(de)(de)(de)基極(ji)(ji)電(dian)流(liu)(liu)(liu)同樣不受(shou)交(jiao)流(liu)(liu)(liu)電(dian)壓(ya)(ya)(ya)(ya)(ya)波動(dong)的(de)(de)(de)(de)(de)影(ying)(ying)響，這就展(zhan)寬了開(kai)關電(dian)海對交(jiao)流(liu)(liu)(liu)輸人(ren)(ren)電(dian)壓(ya)(ya)(ya)(ya)(ya)的(de)(de)(de)(de)(de)適(shi)應范圍。

　　二、開(kai)(kai)關(guan)(guan)中(zhong)楦流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)特點1.含恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)與不(bu)含恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)路(lu)(lu)區別通過(guo)對含恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)和不(bu)含恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)路(lu)(lu)對比，就會(hui)發(fa)現，這兩(liang)(liang)類(lei)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)的(de)(de)振蕩反(fan)(fan)饋(kui)(kui)(kui)支路(lu)(lu)的(de)(de)阻抗是(shi)不(bu)同的(de)(de)（反(fan)(fan)饋(kui)(kui)(kui)支路(lu)(lu)主要(yao)由電(dian)(dian)(dian)(dian)阻和電(dian)(dian)(dian)(dian)容(rong)串聯組成）。附(fu)表是(shi)這兩(liang)(liang)類(lei)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)幾種機心(xin)彩(cai)電(dian)(dian)(dian)(dian)反(fan)(fan)饋(kui)(kui)(kui)電(dian)(dian)(dian)(dian)容(rong)和反(fan)(fan)饋(kui)(kui)(kui)電(dian)(dian)(dian)(dian)阻的(de)(de)統計(ji)表。從統計(ji)表中(zhong)可以看(kan)出：含恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)振蕩反(fan)(fan)饋(kui)(kui)(kui)電(dian)(dian)(dian)(dian)容(rong)小，阻抗大，反(fan)(fan)饋(kui)(kui)(kui)電(dian)(dian)(dian)(dian)流(liu)(liu)小；不(bu)含恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)振蕩反(fan)(fan)饋(kui)(kui)(kui)電(dian)(dian)(dian)(dian)容(rong)大，阻抗小，反(fan)(fan)饋(kui)(kui)(kui)電(dian)(dian)(dian)(dian)流(liu)(liu)大。

　　2.失效后機器的(de)故障表(biao)現開(kai)關電(dian)(dian)(dian)(dian)(dian)源中的(de)恒流(liu)電(dian)(dian)(dian)(dian)(dian)路失效后，注人(ren)開(kai)關管(guan)的(de)基極電(dian)(dian)(dian)(dian)(dian)流(liu)僅(jin)有(you)(you)振(zhen)蕩反饋支路一路電(dian)(dian)(dian)(dian)(dian)流(liu)，只能(neng)維持開(kai)關管(guan)處于弱振(zhen)蕩狀(zhuang)態，開(kai)關電(dian)(dian)(dian)(dian)(dian)源的(de)負載(zai)能(neng)力將會大(da)大(da)降(jiang)低。遙控彩(cai)電(dian)(dian)(dian)(dian)(dian)在待電(dian)(dian)(dian)(dian)(dian)子世界老式彩(cai)電(dian)(dian)(dian)(dian)(dian)加裝(zhuang)哞技討嫡(di)t媒葙f鯰改良方鉉(xuan)李超2.記錄數據安裝(zhuang)前測量(liang)(liang)并記錄彩(cai)電(dian)(dian)(dian)(dian)(dian)各模擬(ni)量(liang)(liang)的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)調(diao)節板(ban)±的(de)運放。農彩(cai)電(dian)(dian)(dian)(dian)(dian)中模擬(ni)量(liang)(liang)控制(zhi)電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)兩(liang)個(ge)指(zhi)標(biao)彩(cai)電(dian)(dian)(dian)(dian)(dian)中有(you)(you)音量(liang)(liang)、亮度等模擬(ni)量(liang)(liang)控制(zhi)電(dian)(dian)(dian)(dian)(dian)路，它們一般用調(diao)節電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)方式進(jin)行(xing)控制(zhi)。在這種電(dian)(dian)(dian)(dian)(dian)路中，控制(zhi)電(dian)(dian)(dian)(dian)(dian)壓(ya)有(you)(you)兩(liang)個(ge)指(zhi)標(biao)。

　　調(diao)節范圍設電位器調(diao)到上、下極限時(shi)，對(dui)應的(de)觸頭(tou)電位分別為(wei)Vh、Vl，則控(kong)制電壓(ya)調(diao)節范圍AV=VH―VL.一般來說厶(si)V越大控(kong)制范圍越寬。但是，過(guo)大的(de)AV會使調(diao)節精度(du)下降，影響圖像或伴音質量，嚴重時(shi)彩電不能(neng)正常工作。

　　平均電位平均電位丫(ya)=丫(ya)11一(yi)￥1/2.丫(ya)的大小直接影響(xiang)控(kong)(kong)制效果。如飽和(he)度控(kong)(kong)制中，V過(guo)小會造成(cheng)圖像飽和(he)度調不起來，色(se)彩很淡(dan)。所(suo)以在加裝遙控(kong)(kong)時，AV和(he)V應(ying)盡可能調整到設計水平。如有困難，以適(shi)當(dang)偏高(gao)為(wei)宜。

　　改良方法(fa)的基本構想1.模擬量(liang)控(kong)制電(dian)(dian)路的特點(dian)老式彩(cai)電(dian)(dian)一般(ban)有四個(ge)模擬量(liang)，如遙控(kong)板(ban)上有四個(ge)相(xiang)應(ying)的模擬量(liang)輸出電(dian)(dian)路，各由三只電(dian)(dian)阻(zu)：輸出電(dian)(dian)阻(zu)，上、下偏(pian)置電(dian)(dian)阻(zu)組成，在中相(xiang)應(ying)的電(dian)(dian)阻(zu)分別是R17、R18、R19.其中，輸出電(dian)(dian)阻(zu)主要(yao)控(kong)制調節范圍(wei)，上、下偏(pian)置電(dian)(dian)阻(zu)主要(yao)控(kong)制平均電(dian)(dian)位。

　　2.現行(xing)的(de)調(diao)(diao)(diao)整方(fang)法及改良安裝說明(ming)書及一般(ban)(ban)資(zi)料上介紹的(de)方(fang)法是，廢除彩(cai)電原有的(de)分壓調(diao)(diao)(diao)節(jie)電路，對遙控板上的(de)電阻進(jin)行(xing)調(diao)(diao)(diao)整。這(zhe)樣須調(diao)(diao)(diao)整的(de)電阻一般(ban)(ban)有12只。在(zai)實際工(gong)作中要選定并(bing)(bing)找到相應的(de)電阻并(bing)(bing)不容易，調(diao)(diao)(diao)整起來反反復(fu)復(fu)，耗時多(duo)，精(jing)度(du)差。

　　從上(shang)(shang)面的分(fen)析中，我們(men)不難發現：如果保留彩電(dian)上(shang)(shang)的分(fen)壓電(dian)路(lu)就可(ke)以省掉遙控(kong)板上(shang)(shang)的分(fen)壓電(dian)路(lu)，這樣需調(diao)整的電(dian)阻由12只(zhi)減為4只(zhi)，大(da)大(da)減少了工作(zuo)量，有利于提高調(diao)整精度(du)。

　　實例-1803PD（S）彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)安裝卓異Z9831遙控(kong)器(qi)為(wei)例，現(xian)介紹(shao)如下：1.準備材料找51kn、200kfl可(ke)調電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻各(ge)一只，按連接，引線(xian)長約30cm.備1/8W電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻若干。機狀(zhuang)態(tai)，行(xing)、場(chang)掃(sao)描電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路停止(zhi)工(gong)(gong)作(zuo)，開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)處于(yu)輕(qing)負(fu)(fu)荷狀(zhuang)態(tai)，即使恒流有問題(ti)也看不出它的(de)故障(zhang)表現(xian)。當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)視(shi)機處于(yu)正常收視(shi)狀(zhuang)態(tai)，特(te)別是電(dian)(dian)(dian)(dian)(dian)(dian)(dian)視(shi)屏幕比(bi)較亮(liang)時(shi)，行(xing)、場(chang)掃(sao)描系統(tong)要消耗(hao)較大的(de)功率(lv)，恒流源(yuan)失效了(le)的(de)開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)難(nan)以負(fu)(fu)擔這(zhe)一重任，開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)將(jiang)會(hui)停止(zhi)工(gong)(gong)作(zuo)。開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)停止(zhi)工(gong)(gong)作(zuo)后，行(xing)、場(chang)掃(sao)描電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路因失去供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)也自然停止(zhi)工(gong)(gong)作(zuo)，這(zhe)時(shi)開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)因失去負(fu)(fu)載(zai)又(you)開(kai)始起振工(gong)(gong)作(zuo)，行(xing)、場(chang)掃(sao)描又(you)得到供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)再(zai)度(du)工(gong)(gong)作(zuo)，開(kai)關管負(fu)(fu)擔加重又(you)停止(zhi)工(gong)(gong)作(zuo)，周而復始，范圍，留(liu)作(zuo)調試標準。實測(ce)數據為(wei)：亮(liang)度(du)：7.4彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路改動關掉彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)拔下插頭，將(jiang)各(ge)模擬量(liang)的(de)控(kong)制端由(you)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位器(qi)的(de)中心抽頭改接到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位器(qi)的(de)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位端，并與遙控(kong)板上相應模擬量(liang)的(de)輸出引線(xian)庫(ku)接，如所示(shi)。

　　4遙(yao)控(kong)板調(diao)整(zheng)拔下(xia)(xia)遙(yao)控(kong)板上各模擬量輸(shu)出(chu)端(duan)的(de)上下(xia)(xia)偏置電阻(zu)(zu)共8只，在其它加裝工作已完成的(de)情況下(xia)(xia)，對各模擬量的(de)輸(shu)出(chu)電阻(zu)(zu)進行調(diao)整(zheng)。以亮度控(kong)制(zhi)為(wei)例，具體步驟(zou)如(ru)下(xia)(xia)：⑴拔下(xia)(xia)輸(shu)出(chu)電阻(zu)(zu)R17，將51M1可(ke)調(diao)電阻(zu)(zu)焊上，通電并用遙(yao)控(kong)將亮度調(diao)到最小。如(ru)果熒光屏不亮，可(ke)用萬用表(biao)監測亮度控(kong)制(zhi)電壓，下(xia)(xia)降到不動為(wei)止。

　　（2）調(diao)(diao)整51kfi可調(diao)(diao)電(dian)阻使(shi)亮(liang)度(du)控(kong)制(zhi)(zhi)電(dian)壓(ya)為(wei)(wei)(wei)7.4V.關機焊下(xia)可調(diao)(diao)電(dian)阻的一端，測(ce)得其(qi)阻值(zhi)為(wei)(wei)(wei)37kfl.⑶重(zhong)新焊上可調(diao)(diao)電(dian)阻并開機，用遙控(kong)器將亮(liang)度(du)調(diao)(diao)到(dao)最大(da)。調(diao)(diao)整可調(diao)(diao)電(dian)阻使(shi)亮(liang)度(du)控(kong)制(zhi)(zhi)電(dian)壓(ya)為(wei)(wei)(wei)7.9V，關機焊下(xia)可調(diao)(diao)電(dian)阻，測(ce)得其(qi)阻值(zhi)為(wei)(wei)(wei)40kft.在步(bu)驟⑵、⑶中。如(ru)果調(diao)(diao)整可調(diao)(diao)電(dian)阻達(da)不到(dao)所需電(dian)壓(ya)，就將可調(diao)(diao)電(dian)阻由51kfl換成200M1后重(zhong)試。

　　⑷一般來(lai)說，選(xuan)擇偏小(xiao)的(de)輸出電阻使調(diao)節范圍適當(dang)擴大為宜，這(zhe)里選(xuan)R17=36kft.經(jing)測(ce)試亮(liang)度控制(zhi)電壓為7.3~8.IV，效果很(hen)理想。如果選(xuan)R17=33kft，效果也不(bu)錯(cuo)。其它三個模擬量輸出電阻的(de)選(xuan)擇方法與此相同，這(zhe)里不(bu)再(zai)贅述(shu)。

　　從上(shang)(shang)(shang)面的(de)(de)介紹中不(bu)難發(fa)現這(zhe)(zhe)種(zhong)方法有三個優點：（1）不(bu)需對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)路進行太多(duo)分析(xi)和(he)了(le)解。⑵需要調整電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)由12只(zhi)變(bian)成4只(zhi)，減少了(le)工作量(liang)。⑶調整精度(du)便(bian)于(yu)(yu)控(kong)(kong)制(zhi)，有利于(yu)(yu)提(ti)高(gao)圖(tu)(tu)像(xiang)(xiang)(xiang)質量(liang)。必須說(shuo)明的(de)(de)是(shi)，這(zhe)(zhe)里介紹的(de)(de)；1一(yi)般(ban)性(xing)的(de)(de)方法，在實(shi)際工作中應靈活運用(yong)(yong)。例如(ru)，在對(dui)本(ben)例的(de)(de)音(yin)量(liang)控(kong)(kong)制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)路進行連接(jie)時(shi)(shi)，可(ke)(ke)將(jiang)(jiang)遙控(kong)(kong)板(ban)(ban)上(shang)(shang)(shang)的(de)(de)三只(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R11、R12、R13拔掉(diao)，將(jiang)(jiang)電(dian)(dian)(dian)(dian)(dian)(dian)視(shi)機(ji)中的(de)(de)R302移到(dao)遙控(kong)(kong)板(ban)(ban)上(shang)(shang)(shang)R11的(de)(de)位置，如(ru)所示，則音(yin)量(liang)控(kong)(kong)制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)0~5.6V，效果不(bu)錯。對(dui)于(yu)(yu)控(kong)(kong)制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)0~12V的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路，如(ru)夏普NC-2T的(de)(de)色度(du)和(he)對(dui)比(bi)度(du)控(kong)(kong)制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)路，可(ke)(ke)將(jiang)(jiang)遙控(kong)(kong)板(ban)(ban)輸(shu)出端的(de)(de)上(shang)(shang)(shang)、下偏(pian)置電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)拔掉(diao)，將(jiang)(jiang)輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)換(huan)成l~2kft即可(ke)(ke)使用(yong)(yong)。這(zhe)(zhe)時(shi)(shi)輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)僅起限流作用(yong)(yong)，以保護(hu)遙控(kong)(kong)開關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源只(zhi)能(neng)處于(yu)(yu)間歇(xie)振蕩(dang)狀態。表(biao)現在電(dian)(dian)(dian)(dian)(dian)(dian)視(shi)屏(ping)幕上(shang)(shang)(shang)的(de)(de)故障現象是(shi)：電(dian)(dian)(dian)(dian)(dian)(dian)視(shi)屏(ping)幕亮(liang)度(du)高(gao)時(shi)(shi)，光(guang)柵會不(bu)斷(duan)地(di)收縮(suo)(suo)。或者當電(dian)(dian)(dian)(dian)(dian)(dian)視(shi)畫(hua)面較暗時(shi)(shi)，圖(tu)(tu)像(xiang)(xiang)(xiang)尚(shang)能(neng)穩(wen)定住(zhu)。當電(dian)(dian)(dian)(dian)(dian)(dian)視(shi)畫(hua)面較亮(liang)時(shi)(shi)，就(jiu)會出現“光(guang)柵不(bu)停地(di)收縮(suo)(suo)――展開一(yi)收縮(suo)(suo)”。這(zhe)(zhe)時(shi)(shi)你測量(liang)+B115V電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，在光(guang)柵收縮(suo)(suo)瞬間會降至70V左右。該電(dian)(dian)(dian)(dian)(dian)(dian)視(shi)機(ji)在調機(ji)進行搜(sou)索(suo)時(shi)(shi)，搜(sou)索(suo)到(dao)的(de)(de)圖(tu)(tu)像(xiang)(xiang)(xiang)比(bi)較暗時(shi)(shi)，可(ke)(ke)以正常搜(sou)索(suo)并存(cun)儲。搜(sou)索(suo)到(dao)的(de)(de)圖(tu)(tu)像(xiang)(xiang)(xiang)較亮(liang)時(shi)(shi)，光(guang)柵來回(hui)閃動(dong)，圖(tu)(tu)像(xiang)(xiang)(xiang)不(bu)穩(wen)定，或同(tong)步不(bu)良，電(dian)(dian)(dian)(dian)(dian)(dian)視(shi)頻(pin)道不(bu)能(neng)存(cun)儲。

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