本文將對開關電源中恒電流源電路(lu)的(de)工作原理(li)及特點等進行分析(xi)，供讀者(zhe)。

　　一、開關電源恒流源電路的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)構成(cheng)及工(gong)作(zuo)原(yuan)理(li)由(you)分(fen)立元件組(zu)成(cheng)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)中的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)恒(heng)(heng)流(liu)源(yuan)(yuan)電(dian)(dian)(dian)路(lu)(lu)由(you)分(fen)立元件組(zu)成(cheng)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)采(cai)用恒(heng)(heng)流(liu)源(yuan)(yuan)電(dian)(dian)(dian)路(lu)(lu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)彩電(dian)(dian)(dian)有：長虹NC-2、NC- 3、A6等機心系列闈電(dian)(dian)(dian)。另外，東芝2929DH/DXH彩3開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)基(ji)本(ben)相(xiang)同，也是采(cai)用恒(heng)(heng)流(liu)源(yuan)(yuan)電(dian)(dian)(dian)揠。，是這種開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)中的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)振(zhen)蕩和(he)恒(heng)(heng)流(liu)源(yuan)(yuan)原(yuan)理(li)圖。振(zhen)蕩‘路(lu)(lu)由(you)-⑨繞組(zu)是振(zhen)蕩電(dian)(dian)(dian)路(lu)(lu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)反饋支路(lu)(lu)。恒(heng)(heng)流(liu)源(yuan)(yuan)由(you)VQ820、R822、VD820、C821、R823、T803⑦~⑧和(he)⑦⑨繞組(zu)構成(cheng)。其(qi)(qi)工(gong)作(zuo)原(yuan)理(li)是：在VQ83截(jie)止(zhi)期(qi)間，T803的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)⑧端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)為正，⑨端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)為負。⑨端(duan)(duan)(duan)(duan)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)負電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)經R823加(jia)到VQ820的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)基(ji)極(ji)，使(shi)VQ820截(jie)止(zhi)。T803⑧端(duan)(duan)(duan)(duan)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)正電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)通過VD820向(xiang)C821充電(dian)(dian)(dian)，C821上(shang)充得的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)就成(cheng)為VQ820導(dao)通時(shi)所(suo)需的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)工(gong)作(zuo)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。VQ83導(dao)通時(shi)，T803⑧端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)變負，⑨端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)由(you)負變正。⑧端(duan)(duan)(duan)(duan)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)負電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)加(jia)到VD820正極(ji)使(shi)其(qi)(qi)截(jie)止(zhi)，⑨端(duan)(duan)(duan)(duan)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)正電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)經R823加(jia)到VQ820基(ji)極(ji)使(shi)其(qi)(qi)導(dao)通。VQ820導(dao)通后(hou)，流(liu)經VQ820集-射之間的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)流(liu)便成(cheng)為VQ83的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)基(ji)極(ji)注人電(dian)(dian)(dian)流(liu)。VQ820的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)導(dao)通電(dian)(dian)(dian)流(liu)不受(shou)交(jiao)(jiao)(jiao)流(liu)輸(shu)人電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)波動的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)影響(xiang)，其(qi)(qi)大小取決于C821上(shang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)和(he)電(dian)(dian)(dian)阻R822的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大小，所(suo)以，VQ83的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)基(ji)極(ji)電(dian)(dian)(dian)流(liu)同樣不受(shou)交(jiao)(jiao)(jiao)流(liu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)波動的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)影響(xiang)，這就展寬了(le)開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)對交(jiao)(jiao)(jiao)流(liu)輸(shu)入電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)適應(ying)范圍。

　　恒流源(yuan)(yuan)電(dian)路(lu)(lu)(lu)6333等(deng)。采用(yong)STR-S6309組成(cheng)開關(guan)(guan)電(dian)源(yuan)(yuan)的彩(cai)電(dian)有：康佳06系列），夏(xia)普25N42-E2、29FN1、29AW1及寬(kuan)屏W288、W328，熊貓C64P2、2919，長城(cheng)G8173MF、G8263、G8363，創維(wei)CTV-8259、CTV-8298.厚膜(mo)電(dian)路(lu)(lu)(lu)STR-S6308與(yu)STR-S6309內部電(dian)路(lu)(lu)(lu)結構基本相(xiang)同(tong)，恒流源(yuan)(yuan)電(dian)路(lu)(lu)(lu)和原理完全相(xiang)同(tong)。下面以STR-S6308厚膜(mo)電(dian)路(lu)(lu)(lu)組成(cheng)的開關(guan)(guan)電(dian)源(yuan)(yuan)為例說明其恒流源(yuan)(yuan)工作原理。

　　是(shi)(shi)STR-6308厚膜電(dian)(dian)(dian)(dian)(dian)路(lu)組成(cheng)的(de)(de)(de)開關(guan)(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)中的(de)(de)(de)振蕩和恒(heng)流(liu)(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)路(lu)原理圖(tu)。圖(tu)中，IC801內部的(de)(de)(de)Q1是(shi)(shi)開關(guan)(guan)管，R803、R804是(shi)(shi)振蕩啟動電(dian)(dian)(dian)(dian)(dian)阻(zu)，C812、R807、T803①-②繞組是(shi)(shi)振蕩電(dian)(dian)(dian)(dian)(dian)路(lu)的(de)(de)(de)反饋支路(lu)。恒(heng)流(liu)(liu)(liu)(liu)(liu)源(yuan)電(dian)(dian)(dian)(dian)(dian)路(lu)由(you)(you)IC801內部的(de)(de)(de)Q3、R2、R3、D2及外部的(de)(de)(de)C814、D803、R806和T803①-②繞組構成(cheng)。其(qi)恒(heng)流(liu)(liu)(liu)(liu)(liu)源(yuan)工作原理為(wei)：在(zai)（1截止(zhi)期間(jian)，T803②端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)正(zheng)(zheng)，①端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)負(fu)。T803②端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)通(tong)(tong)過(guo)IC801內部的(de)(de)(de)D2向C814充電(dian)(dian)(dian)(dian)(dian)，其(qi)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)路(lu)徑為(wei)：T803②④一(yi)814-803-803①。C814上(shang)充得的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)就(jiu)成(cheng)為(wei)Q3導(dao)通(tong)(tong)時所需要的(de)(de)(de)工作電(dian)(dian)(dian)(dian)(dian)壓(ya)。在(zai)Q1導(dao)通(tong)(tong)時，T803②端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)由(you)(you)正(zheng)(zheng)變(bian)(bian)負(fu)，①端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)由(you)(you)負(fu)變(bian)(bian)正(zheng)(zheng)。②端(duan)(duan)的(de)(de)(de)負(fu)電(dian)(dian)(dian)(dian)(dian)壓(ya)加到(dao)D2的(de)(de)(de)正(zheng)(zheng)極(ji)(ji)使其(qi)截止(zhi)，①端(duan)(duan)的(de)(de)(de)正(zheng)(zheng)電(dian)(dian)(dian)(dian)(dian)壓(ya)加到(dao)IC801的(de)(de)(de)⑤腳，再(zai)通(tong)(tong)過(guo)其(qi)內部R3加到(dao)Q3的(de)(de)(de)基極(ji)(ji)使其(qi)導(dao)通(tong)(tong)。Q3導(dao)通(tong)(tong)后，C814通(tong)(tong)過(guo)Q3放(fang)電(dian)(dian)(dian)(dian)(dian)，其(qi)放(fang)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)路(lu)徑為(wei)：C814正(zheng)(zheng)極(ji)(ji)->IC801dH3ce極(ji)(ji)->Qlbe極(ji)(ji)―IC801②―R806->C814負(fu)極(ji)(ji)。Q3導(dao)通(tong)(tong)后，流(liu)(liu)(liu)(liu)(liu)過(guo)Q3集射(she)之間(jian)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)便(bian)成(cheng)為(wei)（1的(de)(de)(de)基極(ji)(ji)注人電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)。因為(wei)Q3的(de)(de)(de)導(dao)通(tong)(tong)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)不受交流(liu)(liu)(liu)(liu)(liu)輸人電(dian)(dian)(dian)(dian)(dian)壓(ya)波(bo)(bo)動的(de)(de)(de)影響，只(zhi)取決于(yu)C814上(shang)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)和電(dian)(dian)(dian)(dian)(dian)阻(zu)R806的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻(zu)大(da)小，所以，開關(guan)(guan)管Q1的(de)(de)(de)基極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)同樣不受交流(liu)(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)壓(ya)波(bo)(bo)動的(de)(de)(de)影響，這就(jiu)展寬了開關(guan)(guan)電(dian)(dian)(dian)(dian)(dian)海對交流(liu)(liu)(liu)(liu)(liu)輸人電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)適應范(fan)圍。

　　二(er)、開(kai)關(guan)中楦流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)路的(de)(de)特點1.含(han)恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)與不含(han)恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)路區(qu)別通(tong)過對含(han)恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)和不含(han)恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)路對比，就會發現，這(zhe)兩類(lei)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)的(de)(de)振(zhen)蕩反(fan)(fan)饋(kui)支路的(de)(de)阻(zu)抗是不同的(de)(de)（反(fan)(fan)饋(kui)支路主要由電(dian)(dian)(dian)(dian)(dian)阻(zu)和電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)串聯(lian)組成）。附表是這(zhe)兩類(lei)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)幾(ji)種機心彩電(dian)(dian)(dian)(dian)(dian)反(fan)(fan)饋(kui)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)和反(fan)(fan)饋(kui)電(dian)(dian)(dian)(dian)(dian)阻(zu)的(de)(de)統計表。從統計表中可以看(kan)出：含(han)恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)振(zhen)蕩反(fan)(fan)饋(kui)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)小(xiao)，阻(zu)抗大，反(fan)(fan)饋(kui)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)小(xiao)；不含(han)恒(heng)(heng)流(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)的(de)(de)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)振(zhen)蕩反(fan)(fan)饋(kui)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)大，阻(zu)抗小(xiao)，反(fan)(fan)饋(kui)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)大。

　　2.失效(xiao)后機器的(de)(de)(de)(de)故(gu)障表現開關電(dian)(dian)(dian)源中(zhong)的(de)(de)(de)(de)恒流電(dian)(dian)(dian)路失效(xiao)后，注人開關管的(de)(de)(de)(de)基極電(dian)(dian)(dian)流僅(jin)有振蕩反饋支(zhi)路一路電(dian)(dian)(dian)流，只能維(wei)持(chi)開關管處于弱振蕩狀態，開關電(dian)(dian)(dian)源的(de)(de)(de)(de)負載(zai)能力將會大大降低。遙控(kong)(kong)彩(cai)(cai)(cai)(cai)電(dian)(dian)(dian)在待(dai)電(dian)(dian)(dian)子世界老式(shi)彩(cai)(cai)(cai)(cai)電(dian)(dian)(dian)加裝(zhuang)(zhuang)哞(mou)技討嫡t媒葙f鯰改良(liang)方鉉李超2.記錄數據安裝(zhuang)(zhuang)前測量(liang)并記錄彩(cai)(cai)(cai)(cai)電(dian)(dian)(dian)各模(mo)擬量(liang)的(de)(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)調節(jie)板±的(de)(de)(de)(de)運放(fang)。農彩(cai)(cai)(cai)(cai)電(dian)(dian)(dian)中(zhong)模(mo)擬量(liang)控(kong)(kong)制(zhi)電(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)兩(liang)個(ge)指(zhi)標彩(cai)(cai)(cai)(cai)電(dian)(dian)(dian)中(zhong)有音量(liang)、亮度等(deng)模(mo)擬量(liang)控(kong)(kong)制(zhi)電(dian)(dian)(dian)路，它(ta)們一般用調節(jie)電(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)方式(shi)進(jin)行控(kong)(kong)制(zhi)。在這種電(dian)(dian)(dian)路中(zhong)，控(kong)(kong)制(zhi)電(dian)(dian)(dian)壓(ya)(ya)有兩(liang)個(ge)指(zhi)標。

　　調(diao)節(jie)(jie)范(fan)圍設(she)電(dian)(dian)位(wei)(wei)器調(diao)到上、下(xia)極限時，對應的(de)觸頭電(dian)(dian)位(wei)(wei)分別為Vh、Vl，則控制電(dian)(dian)壓(ya)調(diao)節(jie)(jie)范(fan)圍AV=VH―VL.一(yi)般來說(shuo)厶V越大控制范(fan)圍越寬。但是(shi)，過大的(de)AV會使(shi)調(diao)節(jie)(jie)精度下(xia)降，影響圖像或(huo)伴音(yin)質量，嚴重時彩電(dian)(dian)不能正常工作。

　　平均電(dian)位(wei)平均電(dian)位(wei)丫=丫11一￥1/2.丫的大小直(zhi)接影響控(kong)制效果。如飽和(he)度控(kong)制中，V過小會(hui)造成圖像飽和(he)度調不起來，色彩(cai)很淡(dan)。所以(yi)在(zai)加裝(zhuang)遙控(kong)時，AV和(he)V應盡可能調整到(dao)設計水平。如有困難，以(yi)適當偏高(gao)為宜(yi)。

　　改良方法的(de)基本構想1.模擬量控(kong)(kong)制(zhi)電(dian)(dian)路的(de)特點老(lao)式彩電(dian)(dian)一般有(you)四(si)個模擬量，如遙控(kong)(kong)板上(shang)(shang)有(you)四(si)個相應的(de)模擬量輸出(chu)電(dian)(dian)路，各由三(san)只電(dian)(dian)阻(zu)：輸出(chu)電(dian)(dian)阻(zu)，上(shang)(shang)、下(xia)偏置電(dian)(dian)阻(zu)組成，在中相應的(de)電(dian)(dian)阻(zu)分別是R17、R18、R19.其中，輸出(chu)電(dian)(dian)阻(zu)主(zhu)要(yao)控(kong)(kong)制(zhi)調節范圍，上(shang)(shang)、下(xia)偏置電(dian)(dian)阻(zu)主(zhu)要(yao)控(kong)(kong)制(zhi)平均(jun)電(dian)(dian)位。

　　2.現行(xing)的(de)調(diao)(diao)整(zheng)方(fang)法及(ji)改良(liang)安裝說明(ming)書及(ji)一般資(zi)料上介紹的(de)方(fang)法是，廢(fei)除彩電(dian)(dian)原有(you)的(de)分壓調(diao)(diao)節電(dian)(dian)路，對遙控板上的(de)電(dian)(dian)阻進行(xing)調(diao)(diao)整(zheng)。這(zhe)樣須調(diao)(diao)整(zheng)的(de)電(dian)(dian)阻一般有(you)12只(zhi)。在實際工作中要選(xuan)定并找(zhao)到相應的(de)電(dian)(dian)阻并不容易，調(diao)(diao)整(zheng)起(qi)來反反復復，耗(hao)時(shi)多，精(jing)度(du)差。

　　從上面的(de)分析中，我們不難發現：如果保留(liu)彩電(dian)上的(de)分壓電(dian)路就可以(yi)省掉遙控板上的(de)分壓電(dian)路，這樣需(xu)調整的(de)電(dian)阻由12只減為4只，大大減少了工(gong)作量(liang)，有利于提高調整精度。

　　實例-1803PD（S）彩電(dian)(dian)(dian)(dian)安(an)裝卓異(yi)Z9831遙控(kong)器為例，現介(jie)紹如下：1.準(zhun)(zhun)備材料找51kn、200kfl可調(diao)電(dian)(dian)(dian)(dian)阻各一只(zhi)，按連(lian)接(jie)，引線(xian)長約30cm.備1/8W電(dian)(dian)(dian)(dian)阻若干。機狀(zhuang)(zhuang)態(tai)，行(xing)、場掃描(miao)電(dian)(dian)(dian)(dian)路停(ting)(ting)止(zhi)工作(zuo)(zuo)，開(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)處于(yu)輕負(fu)荷(he)狀(zhuang)(zhuang)態(tai)，即使(shi)恒流有(you)問題(ti)也看不出它的故障(zhang)表現。當電(dian)(dian)(dian)(dian)視機處于(yu)正常收(shou)視狀(zhuang)(zhuang)態(tai)，特(te)別是(shi)電(dian)(dian)(dian)(dian)視屏幕比(bi)較亮(liang)(liang)時，行(xing)、場掃描(miao)系統要消耗較大(da)的功率，恒流源(yuan)(yuan)失效了的開(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)難以負(fu)擔這一重任，開(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)將會(hui)停(ting)(ting)止(zhi)工作(zuo)(zuo)。開(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)停(ting)(ting)止(zhi)工作(zuo)(zuo)后，行(xing)、場掃描(miao)電(dian)(dian)(dian)(dian)路因失去(qu)供電(dian)(dian)(dian)(dian)也自然停(ting)(ting)止(zhi)工作(zuo)(zuo)，這時開(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)因失去(qu)負(fu)載又(you)開(kai)始起振工作(zuo)(zuo)，行(xing)、場掃描(miao)又(you)得到(dao)供電(dian)(dian)(dian)(dian)再度工作(zuo)(zuo)，開(kai)關(guan)(guan)管負(fu)擔加重又(you)停(ting)(ting)止(zhi)工作(zuo)(zuo)，周而復始，范圍，留作(zuo)(zuo)調(diao)試標(biao)準(zhun)(zhun)。實測數(shu)據為：亮(liang)(liang)度：7.4彩電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)路改動關(guan)(guan)掉彩電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源(yuan)(yuan)拔(ba)下插頭(tou)(tou)，將各模擬量(liang)的控(kong)制端(duan)由電(dian)(dian)(dian)(dian)位(wei)器的中心(xin)抽(chou)頭(tou)(tou)改接(jie)到(dao)電(dian)(dian)(dian)(dian)位(wei)器的高電(dian)(dian)(dian)(dian)位(wei)端(duan)，并(bing)與(yu)遙控(kong)板上(shang)相(xiang)應模擬量(liang)的輸出引線(xian)庫接(jie)，如所示。

　　4遙(yao)控(kong)板調(diao)整(zheng)拔下遙(yao)控(kong)板上各模擬量(liang)輸出(chu)端的上下偏置電(dian)(dian)阻(zu)共(gong)8只，在其它加裝工(gong)作已完(wan)成(cheng)的情況下，對各模擬量(liang)的輸出(chu)電(dian)(dian)阻(zu)進行調(diao)整(zheng)。以亮(liang)(liang)(liang)度控(kong)制(zhi)為例(li)，具(ju)體步驟如下：⑴拔下輸出(chu)電(dian)(dian)阻(zu)R17，將51M1可調(diao)電(dian)(dian)阻(zu)焊上，通(tong)電(dian)(dian)并用(yong)遙(yao)控(kong)將亮(liang)(liang)(liang)度調(diao)到(dao)最(zui)小。如果熒光屏不亮(liang)(liang)(liang)，可用(yong)萬用(yong)表監測亮(liang)(liang)(liang)度控(kong)制(zhi)電(dian)(dian)壓，下降到(dao)不動為止。

　　（2）調(diao)(diao)(diao)(diao)整51kfi可(ke)(ke)調(diao)(diao)(diao)(diao)電(dian)阻(zu)(zu)(zu)使(shi)亮度(du)控(kong)制電(dian)壓(ya)為(wei)(wei)7.4V.關(guan)機焊(han)(han)下(xia)可(ke)(ke)調(diao)(diao)(diao)(diao)電(dian)阻(zu)(zu)(zu)的一端(duan)，測(ce)得其阻(zu)(zu)(zu)值(zhi)為(wei)(wei)37kfl.⑶重新(xin)焊(han)(han)上可(ke)(ke)調(diao)(diao)(diao)(diao)電(dian)阻(zu)(zu)(zu)并開機，用(yong)遙控(kong)器(qi)將亮度(du)調(diao)(diao)(diao)(diao)到最大。調(diao)(diao)(diao)(diao)整可(ke)(ke)調(diao)(diao)(diao)(diao)電(dian)阻(zu)(zu)(zu)使(shi)亮度(du)控(kong)制電(dian)壓(ya)為(wei)(wei)7.9V，關(guan)機焊(han)(han)下(xia)可(ke)(ke)調(diao)(diao)(diao)(diao)電(dian)阻(zu)(zu)(zu)，測(ce)得其阻(zu)(zu)(zu)值(zhi)為(wei)(wei)40kft.在步驟⑵、⑶中。如(ru)果調(diao)(diao)(diao)(diao)整可(ke)(ke)調(diao)(diao)(diao)(diao)電(dian)阻(zu)(zu)(zu)達不到所需電(dian)壓(ya)，就將可(ke)(ke)調(diao)(diao)(diao)(diao)電(dian)阻(zu)(zu)(zu)由51kfl換成200M1后重試。

　　⑷一般來說，選擇偏(pian)小的輸出電(dian)(dian)阻使調節范圍適當擴大為宜，這里選R17=36kft.經測試亮度控制電(dian)(dian)壓為7.3~8.IV，效(xiao)果很理想。如果選R17=33kft，效(xiao)果也不錯。其(qi)它(ta)三個模擬量輸出電(dian)(dian)阻的選擇方(fang)法(fa)與此相同，這里不再贅述。

　　從上面的介紹(shao)中不(bu)難發現這種方(fang)(fang)法有三個優點：（1）不(bu)需(xu)對(dui)電(dian)(dian)(dian)(dian)路進(jin)行太多(duo)分析和了(le)解。⑵需(xu)要調(diao)(diao)整(zheng)電(dian)(dian)(dian)(dian)阻(zu)由12只(zhi)變(bian)成4只(zhi)，減少(shao)了(le)工作(zuo)量。⑶調(diao)(diao)整(zheng)精度便(bian)于(yu)(yu)控(kong)(kong)制，有利于(yu)(yu)提高(gao)圖像(xiang)質(zhi)量。必須說明的是，這里介紹(shao)的；1一(yi)般性(xing)的方(fang)(fang)法，在實(shi)際工作(zuo)中應靈活運用(yong)。例如，在對(dui)本例的音量控(kong)(kong)制電(dian)(dian)(dian)(dian)路進(jin)行連接時(shi)(shi)，可將(jiang)遙(yao)(yao)控(kong)(kong)板(ban)上的三只(zhi)電(dian)(dian)(dian)(dian)阻(zu)R11、R12、R13拔掉，將(jiang)電(dian)(dian)(dian)(dian)視(shi)機(ji)中的R302移到(dao)遙(yao)(yao)控(kong)(kong)板(ban)上R11的位置(zhi)，如所(suo)示，則音量控(kong)(kong)制電(dian)(dian)(dian)(dian)壓為0~5.6V，效果不(bu)錯。對(dui)于(yu)(yu)控(kong)(kong)制電(dian)(dian)(dian)(dian)壓為0~12V的電(dian)(dian)(dian)(dian)路，如夏普NC-2T的色度和對(dui)比(bi)度控(kong)(kong)制電(dian)(dian)(dian)(dian)路，可將(jiang)遙(yao)(yao)控(kong)(kong)板(ban)輸(shu)(shu)出端(duan)的上、下偏置(zhi)電(dian)(dian)(dian)(dian)阻(zu)拔掉，將(jiang)輸(shu)(shu)出電(dian)(dian)(dian)(dian)阻(zu)換成l~2kft即可使用(yong)。這時(shi)(shi)輸(shu)(shu)出電(dian)(dian)(dian)(dian)阻(zu)僅起限流作(zuo)用(yong)，以保護遙(yao)(yao)控(kong)(kong)開關(guan)電(dian)(dian)(dian)(dian)源(yuan)只(zhi)能處于(yu)(yu)間(jian)(jian)歇振蕩狀態。表現在電(dian)(dian)(dian)(dian)視(shi)屏(ping)幕上的故障現象是：電(dian)(dian)(dian)(dian)視(shi)屏(ping)幕亮(liang)度高(gao)時(shi)(shi)，光柵(zha)(zha)(zha)會不(bu)斷地(di)收(shou)(shou)縮。或(huo)者(zhe)當(dang)(dang)電(dian)(dian)(dian)(dian)視(shi)畫面較(jiao)暗(an)時(shi)(shi)，圖像(xiang)尚能穩定住。當(dang)(dang)電(dian)(dian)(dian)(dian)視(shi)畫面較(jiao)亮(liang)時(shi)(shi)，就(jiu)會出現“光柵(zha)(zha)(zha)不(bu)停(ting)地(di)收(shou)(shou)縮――展開一(yi)收(shou)(shou)縮”。這時(shi)(shi)你測(ce)量+B115V電(dian)(dian)(dian)(dian)壓，在光柵(zha)(zha)(zha)收(shou)(shou)縮瞬間(jian)(jian)會降至70V左右。該電(dian)(dian)(dian)(dian)視(shi)機(ji)在調(diao)(diao)機(ji)進(jin)行搜(sou)索時(shi)(shi)，搜(sou)索到(dao)的圖像(xiang)比(bi)較(jiao)暗(an)時(shi)(shi)，可以正(zheng)常(chang)搜(sou)索并存儲。搜(sou)索到(dao)的圖像(xiang)較(jiao)亮(liang)時(shi)(shi)，光柵(zha)(zha)(zha)來回閃(shan)動(dong)，圖像(xiang)不(bu)穩定，或(huo)同步不(bu)良，電(dian)(dian)(dian)(dian)視(shi)頻道不(bu)能存儲。

                                                                                                                   本(ben)文摘自于中國鋰電網