本文將對開關(guan)電(dian)源中恒電(dian)流源電(dian)路(lu)的工作原理及特點等進行(xing)分析，供讀者。

　　一、開關電源恒流源電路的(de)(de)(de)構(gou)成(cheng)(cheng)(cheng)及工(gong)作原理由分(fen)立元(yuan)件組(zu)成(cheng)(cheng)(cheng)的(de)(de)(de)開關(guan)電(dian)(dian)(dian)源(yuan)(yuan)中的(de)(de)(de)恒(heng)(heng)流(liu)源(yuan)(yuan)電(dian)(dian)(dian)路(lu)(lu)由分(fen)立元(yuan)件組(zu)成(cheng)(cheng)(cheng)的(de)(de)(de)開關(guan)電(dian)(dian)(dian)源(yuan)(yuan)采用恒(heng)(heng)流(liu)源(yuan)(yuan)電(dian)(dian)(dian)路(lu)(lu)的(de)(de)(de)彩電(dian)(dian)(dian)有：長(chang)虹NC-2、NC- 3、A6等機心系列闈(wei)電(dian)(dian)(dian)。另外，東芝2929DH/DXH彩3開關(guan)電(dian)(dian)(dian)源(yuan)(yuan)基(ji)(ji)本相同(tong)(tong)，也是(shi)(shi)采用恒(heng)(heng)流(liu)源(yuan)(yuan)電(dian)(dian)(dian)揠。，是(shi)(shi)這種開關(guan)電(dian)(dian)(dian)源(yuan)(yuan)中的(de)(de)(de)振(zhen)蕩(dang)和(he)恒(heng)(heng)流(liu)源(yuan)(yuan)原理圖。振(zhen)蕩(dang)‘路(lu)(lu)由-⑨繞組(zu)是(shi)(shi)振(zhen)蕩(dang)電(dian)(dian)(dian)路(lu)(lu)的(de)(de)(de)反饋(kui)支路(lu)(lu)。恒(heng)(heng)流(liu)源(yuan)(yuan)由VQ820、R822、VD820、C821、R823、T803⑦~⑧和(he)⑦⑨繞組(zu)構(gou)成(cheng)(cheng)(cheng)。其(qi)(qi)(qi)工(gong)作原理是(shi)(shi)：在VQ83截止(zhi)期間(jian)，T803的(de)(de)(de)⑧端(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)為正(zheng)，⑨端(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)為負(fu)。⑨端(duan)的(de)(de)(de)負(fu)電(dian)(dian)(dian)壓(ya)(ya)(ya)經R823加(jia)到VQ820的(de)(de)(de)基(ji)(ji)極，使(shi)VQ820截止(zhi)。T803⑧端(duan)的(de)(de)(de)正(zheng)電(dian)(dian)(dian)壓(ya)(ya)(ya)通(tong)(tong)過VD820向C821充電(dian)(dian)(dian)，C821上(shang)充得的(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)(ya)就成(cheng)(cheng)(cheng)為VQ820導通(tong)(tong)時所(suo)需的(de)(de)(de)工(gong)作電(dian)(dian)(dian)壓(ya)(ya)(ya)。VQ83導通(tong)(tong)時，T803⑧端(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)變(bian)負(fu)，⑨端(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)由負(fu)變(bian)正(zheng)。⑧端(duan)的(de)(de)(de)負(fu)電(dian)(dian)(dian)壓(ya)(ya)(ya)加(jia)到VD820正(zheng)極使(shi)其(qi)(qi)(qi)截止(zhi)，⑨端(duan)的(de)(de)(de)正(zheng)電(dian)(dian)(dian)壓(ya)(ya)(ya)經R823加(jia)到VQ820基(ji)(ji)極使(shi)其(qi)(qi)(qi)導通(tong)(tong)。VQ820導通(tong)(tong)后，流(liu)經VQ820集(ji)-射之間(jian)的(de)(de)(de)電(dian)(dian)(dian)流(liu)便成(cheng)(cheng)(cheng)為VQ83的(de)(de)(de)基(ji)(ji)極注人電(dian)(dian)(dian)流(liu)。VQ820的(de)(de)(de)導通(tong)(tong)電(dian)(dian)(dian)流(liu)不(bu)受交(jiao)流(liu)輸人電(dian)(dian)(dian)壓(ya)(ya)(ya)波動的(de)(de)(de)影響，其(qi)(qi)(qi)大(da)小(xiao)(xiao)取(qu)決于C821上(shang)的(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)(ya)和(he)電(dian)(dian)(dian)阻(zu)R822的(de)(de)(de)大(da)小(xiao)(xiao)，所(suo)以，VQ83的(de)(de)(de)基(ji)(ji)極電(dian)(dian)(dian)流(liu)同(tong)(tong)樣不(bu)受交(jiao)流(liu)電(dian)(dian)(dian)壓(ya)(ya)(ya)波動的(de)(de)(de)影響，這就展(zhan)寬了開關(guan)電(dian)(dian)(dian)源(yuan)(yuan)對交(jiao)流(liu)輸入(ru)電(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)(de)適應(ying)范圍(wei)。

　　恒流(liu)源電(dian)(dian)(dian)路(lu)6333等(deng)。采用STR-S6309組(zu)成(cheng)(cheng)開關(guan)電(dian)(dian)(dian)源的(de)彩電(dian)(dian)(dian)有：康佳06系列），夏普25N42-E2、29FN1、29AW1及寬屏W288、W328，熊(xiong)貓C64P2、2919，長城G8173MF、G8263、G8363，創維CTV-8259、CTV-8298.厚膜電(dian)(dian)(dian)路(lu)STR-S6308與(yu)STR-S6309內(nei)部電(dian)(dian)(dian)路(lu)結構基本相(xiang)同(tong)，恒流(liu)源電(dian)(dian)(dian)路(lu)和原理(li)完(wan)全相(xiang)同(tong)。下面以STR-S6308厚膜電(dian)(dian)(dian)路(lu)組(zu)成(cheng)(cheng)的(de)開關(guan)電(dian)(dian)(dian)源為例(li)說明其恒流(liu)源工作原理(li)。

　　是STR-6308厚膜電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路組(zu)成(cheng)的(de)(de)(de)開關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源中的(de)(de)(de)振(zhen)蕩和(he)恒(heng)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路原理(li)圖。圖中，IC801內(nei)部(bu)(bu)的(de)(de)(de)Q1是開關管(guan)(guan)，R803、R804是振(zhen)蕩啟動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，C812、R807、T803①-②繞組(zu)是振(zhen)蕩電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路的(de)(de)(de)反饋支路。恒(heng)流(liu)(liu)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路由(you)IC801內(nei)部(bu)(bu)的(de)(de)(de)Q3、R2、R3、D2及外(wai)部(bu)(bu)的(de)(de)(de)C814、D803、R806和(he)T803①-②繞組(zu)構成(cheng)。其(qi)恒(heng)流(liu)(liu)源工(gong)作原理(li)為(wei)(wei)：在(zai)（1截(jie)止期間(jian)，T803②端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)(wei)正(zheng)，①端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)(wei)負(fu)(fu)。T803②端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)通過(guo)(guo)IC801內(nei)部(bu)(bu)的(de)(de)(de)D2向C814充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其(qi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)路徑為(wei)(wei)：T803②④一814-803-803①。C814上充(chong)(chong)得的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)就成(cheng)為(wei)(wei)Q3導(dao)通時(shi)所需要的(de)(de)(de)工(gong)作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。在(zai)Q1導(dao)通時(shi)，T803②端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)由(you)正(zheng)變負(fu)(fu)，①端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)由(you)負(fu)(fu)變正(zheng)。②端(duan)(duan)(duan)(duan)的(de)(de)(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)加(jia)到(dao)D2的(de)(de)(de)正(zheng)極(ji)使其(qi)截(jie)止，①端(duan)(duan)(duan)(duan)的(de)(de)(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)加(jia)到(dao)IC801的(de)(de)(de)⑤腳(jiao)，再通過(guo)(guo)其(qi)內(nei)部(bu)(bu)R3加(jia)到(dao)Q3的(de)(de)(de)基(ji)極(ji)使其(qi)導(dao)通。Q3導(dao)通后(hou)，C814通過(guo)(guo)Q3放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其(qi)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)路徑為(wei)(wei)：C814正(zheng)極(ji)->IC801dH3ce極(ji)->Qlbe極(ji)―IC801②―R806->C814負(fu)(fu)極(ji)。Q3導(dao)通后(hou)，流(liu)(liu)過(guo)(guo)Q3集(ji)射之間(jian)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)便成(cheng)為(wei)(wei)（1的(de)(de)(de)基(ji)極(ji)注人(ren)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。因為(wei)(wei)Q3的(de)(de)(de)導(dao)通電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)不受交流(liu)(liu)輸(shu)(shu)人(ren)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)波(bo)動(dong)(dong)的(de)(de)(de)影響(xiang)，只取決于C814上的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)和(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R806的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)大小，所以，開關管(guan)(guan)Q1的(de)(de)(de)基(ji)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)同樣不受交流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)波(bo)動(dong)(dong)的(de)(de)(de)影響(xiang)，這(zhe)就展寬了開關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)海對交流(liu)(liu)輸(shu)(shu)人(ren)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)適應范圍。

　　二、開(kai)(kai)關(guan)(guan)(guan)中(zhong)楦流(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)電(dian)(dian)(dian)(dian)路(lu)的(de)特點(dian)1.含(han)(han)(han)恒流(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)的(de)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)與不含(han)(han)(han)恒流(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)的(de)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)電(dian)(dian)(dian)(dian)路(lu)區別通過(guo)對含(han)(han)(han)恒流(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)和(he)(he)不含(han)(han)(han)恒流(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)電(dian)(dian)(dian)(dian)路(lu)對比(bi)，就(jiu)會(hui)發現(xian)，這兩(liang)類電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)振(zhen)蕩(dang)(dang)(dang)反饋(kui)支路(lu)的(de)阻(zu)抗是不同(tong)的(de)（反饋(kui)支路(lu)主要由電(dian)(dian)(dian)(dian)阻(zu)和(he)(he)電(dian)(dian)(dian)(dian)容(rong)(rong)串聯(lian)組(zu)成）。附表是這兩(liang)類電(dian)(dian)(dian)(dian)源(yuan)(yuan)幾種機心彩電(dian)(dian)(dian)(dian)反饋(kui)電(dian)(dian)(dian)(dian)容(rong)(rong)和(he)(he)反饋(kui)電(dian)(dian)(dian)(dian)阻(zu)的(de)統計表。從(cong)統計表中(zhong)可以看出：含(han)(han)(han)恒流(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)的(de)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)振(zhen)蕩(dang)(dang)(dang)反饋(kui)電(dian)(dian)(dian)(dian)容(rong)(rong)小(xiao)，阻(zu)抗大，反饋(kui)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)小(xiao)；不含(han)(han)(han)恒流(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)的(de)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)振(zhen)蕩(dang)(dang)(dang)反饋(kui)電(dian)(dian)(dian)(dian)容(rong)(rong)大，阻(zu)抗小(xiao)，反饋(kui)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)大。

　　2.失(shi)效后機器的(de)(de)故障表(biao)現(xian)開(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源中(zhong)(zhong)的(de)(de)恒流電(dian)(dian)(dian)(dian)路(lu)失(shi)效后，注人開(kai)關(guan)(guan)管的(de)(de)基極電(dian)(dian)(dian)(dian)流僅有(you)振(zhen)(zhen)蕩反饋支路(lu)一路(lu)電(dian)(dian)(dian)(dian)流，只能維持開(kai)關(guan)(guan)管處于弱振(zhen)(zhen)蕩狀態，開(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源的(de)(de)負載能力將會大大降低。遙控(kong)(kong)(kong)彩(cai)(cai)電(dian)(dian)(dian)(dian)在(zai)待電(dian)(dian)(dian)(dian)子世界老式(shi)彩(cai)(cai)電(dian)(dian)(dian)(dian)加裝(zhuang)哞技討嫡t媒葙f鯰(nian)改良方鉉李超2.記錄數據安(an)裝(zhuang)前測量(liang)(liang)并記錄彩(cai)(cai)電(dian)(dian)(dian)(dian)各模(mo)擬量(liang)(liang)的(de)(de)電(dian)(dian)(dian)(dian)壓調節(jie)板±的(de)(de)運放。農彩(cai)(cai)電(dian)(dian)(dian)(dian)中(zhong)(zhong)模(mo)擬量(liang)(liang)控(kong)(kong)(kong)制(zhi)電(dian)(dian)(dian)(dian)壓的(de)(de)兩(liang)個指標(biao)彩(cai)(cai)電(dian)(dian)(dian)(dian)中(zhong)(zhong)有(you)音量(liang)(liang)、亮度(du)等(deng)模(mo)擬量(liang)(liang)控(kong)(kong)(kong)制(zhi)電(dian)(dian)(dian)(dian)路(lu)，它(ta)們(men)一般(ban)用調節(jie)電(dian)(dian)(dian)(dian)壓的(de)(de)方式(shi)進行控(kong)(kong)(kong)制(zhi)。在(zai)這種電(dian)(dian)(dian)(dian)路(lu)中(zhong)(zhong)，控(kong)(kong)(kong)制(zhi)電(dian)(dian)(dian)(dian)壓有(you)兩(liang)個指標(biao)。

　　調(diao)節范圍設電位(wei)器調(diao)到(dao)上、下極限時，對應的觸頭電位(wei)分別為Vh、Vl，則(ze)控制電壓調(diao)節范圍AV=VH―VL.一般來(lai)說厶(si)V越大控制范圍越寬。但是(shi)，過大的AV會使調(diao)節精度下降，影響圖像或伴音(yin)質量，嚴重時彩(cai)電不能(neng)正常工作。

　　平(ping)均(jun)電位(wei)平(ping)均(jun)電位(wei)丫(ya)=丫(ya)11一￥1/2.丫(ya)的大小直接影(ying)響控(kong)(kong)制效果。如飽(bao)和度控(kong)(kong)制中，V過(guo)小會造(zao)成圖像飽(bao)和度調不起來，色(se)彩(cai)很淡。所(suo)以在加(jia)裝(zhuang)遙控(kong)(kong)時，AV和V應盡可能調整(zheng)到(dao)設計水平(ping)。如有(you)困(kun)難，以適當(dang)偏高為(wei)宜。

　　改良(liang)方法(fa)的(de)基(ji)本(ben)構想1.模(mo)擬(ni)量(liang)控制電路的(de)特點老式彩電一般(ban)有(you)四(si)個模(mo)擬(ni)量(liang)，如(ru)遙控板上(shang)有(you)四(si)個相(xiang)應的(de)模(mo)擬(ni)量(liang)輸(shu)出(chu)電路，各由三只電阻(zu)(zu)(zu)：輸(shu)出(chu)電阻(zu)(zu)(zu)，上(shang)、下(xia)(xia)偏置電阻(zu)(zu)(zu)組成，在中(zhong)相(xiang)應的(de)電阻(zu)(zu)(zu)分別(bie)是(shi)R17、R18、R19.其中(zhong)，輸(shu)出(chu)電阻(zu)(zu)(zu)主(zhu)要控制調節(jie)范圍，上(shang)、下(xia)(xia)偏置電阻(zu)(zu)(zu)主(zhu)要控制平(ping)均電位。

　　2.現行的(de)(de)(de)調(diao)整(zheng)方法(fa)及改(gai)良(liang)安裝(zhuang)說(shuo)明書及一(yi)般資料上介紹的(de)(de)(de)方法(fa)是，廢除彩電(dian)原有的(de)(de)(de)分(fen)壓調(diao)節電(dian)路，對遙控(kong)板上的(de)(de)(de)電(dian)阻(zu)(zu)進(jin)行調(diao)整(zheng)。這樣須調(diao)整(zheng)的(de)(de)(de)電(dian)阻(zu)(zu)一(yi)般有12只。在(zai)實際工作中(zhong)要(yao)選定并(bing)找到相應的(de)(de)(de)電(dian)阻(zu)(zu)并(bing)不容易(yi)，調(diao)整(zheng)起來反(fan)反(fan)復(fu)復(fu)，耗時多，精度差(cha)。

　　從上面的分析中(zhong)，我(wo)們不難發現：如果保留(liu)彩電(dian)上的分壓(ya)電(dian)路就(jiu)可(ke)以省掉遙控板上的分壓(ya)電(dian)路，這(zhe)樣需(xu)調(diao)整的電(dian)阻由12只減為4只，大大減少了工作(zuo)量，有利于提高調(diao)整精度。

　　實例-1803PD（S）彩電(dian)安裝卓異Z9831遙控(kong)器(qi)為例，現(xian)介紹如下(xia)：1.準備(bei)材料找51kn、200kfl可調(diao)電(dian)阻各一只，按連接，引線(xian)長(chang)約(yue)30cm.備(bei)1/8W電(dian)阻若干。機狀態(tai)(tai)，行(xing)、場(chang)掃(sao)描電(dian)路(lu)停止(zhi)工(gong)作(zuo)，開(kai)(kai)關(guan)(guan)(guan)電(dian)源(yuan)(yuan)(yuan)處于輕負(fu)荷狀態(tai)(tai)，即使恒流有問題也(ye)看不出它的(de)故(gu)障表現(xian)。當電(dian)視(shi)機處于正常(chang)收視(shi)狀態(tai)(tai)，特別是電(dian)視(shi)屏(ping)幕比較亮時，行(xing)、場(chang)掃(sao)描系統要消耗較大的(de)功率，恒流源(yuan)(yuan)(yuan)失效了的(de)開(kai)(kai)關(guan)(guan)(guan)電(dian)源(yuan)(yuan)(yuan)難(nan)以(yi)負(fu)擔這(zhe)一重(zhong)任，開(kai)(kai)關(guan)(guan)(guan)電(dian)源(yuan)(yuan)(yuan)將(jiang)會(hui)停止(zhi)工(gong)作(zuo)。開(kai)(kai)關(guan)(guan)(guan)電(dian)源(yuan)(yuan)(yuan)停止(zhi)工(gong)作(zuo)后，行(xing)、場(chang)掃(sao)描電(dian)路(lu)因失去供電(dian)也(ye)自然停止(zhi)工(gong)作(zuo)，這(zhe)時開(kai)(kai)關(guan)(guan)(guan)電(dian)源(yuan)(yuan)(yuan)因失去負(fu)載又開(kai)(kai)始起振(zhen)工(gong)作(zuo)，行(xing)、場(chang)掃(sao)描又得到(dao)供電(dian)再度工(gong)作(zuo)，開(kai)(kai)關(guan)(guan)(guan)管負(fu)擔加重(zhong)又停止(zhi)工(gong)作(zuo)，周而復始，范圍，留作(zuo)調(diao)試(shi)標準。實測(ce)數據為：亮度：7.4彩電(dian)電(dian)路(lu)改動關(guan)(guan)(guan)掉彩電(dian)電(dian)源(yuan)(yuan)(yuan)拔下(xia)插(cha)頭(tou)，將(jiang)各模擬(ni)量的(de)控(kong)制端由電(dian)位器(qi)的(de)中心抽頭(tou)改接到(dao)電(dian)位器(qi)的(de)高(gao)電(dian)位端，并(bing)與(yu)遙控(kong)板上相應模擬(ni)量的(de)輸(shu)出引線(xian)庫接，如所示。

　　4遙(yao)控(kong)板調(diao)(diao)整拔下(xia)(xia)遙(yao)控(kong)板上各模擬量(liang)輸出端的上下(xia)(xia)偏置(zhi)電(dian)阻(zu)共(gong)8只，在其(qi)它(ta)加裝工作(zuo)已完成的情況(kuang)下(xia)(xia)，對各模擬量(liang)的輸出電(dian)阻(zu)進行(xing)調(diao)(diao)整。以(yi)亮度(du)控(kong)制為例，具(ju)體步(bu)驟如下(xia)(xia)：⑴拔下(xia)(xia)輸出電(dian)阻(zu)R17，將51M1可調(diao)(diao)電(dian)阻(zu)焊上，通電(dian)并(bing)用遙(yao)控(kong)將亮度(du)調(diao)(diao)到最小。如果熒光(guang)屏不(bu)亮，可用萬用表監(jian)測亮度(du)控(kong)制電(dian)壓，下(xia)(xia)降到不(bu)動為止。

　　（2）調(diao)整51kfi可(ke)(ke)調(diao)電阻(zu)(zu)(zu)使亮度(du)控(kong)制電壓為7.4V.關(guan)機焊(han)(han)下可(ke)(ke)調(diao)電阻(zu)(zu)(zu)的一(yi)端，測得其阻(zu)(zu)(zu)值為37kfl.⑶重新(xin)焊(han)(han)上可(ke)(ke)調(diao)電阻(zu)(zu)(zu)并開機，用遙控(kong)器(qi)將(jiang)亮度(du)調(diao)到最(zui)大。調(diao)整可(ke)(ke)調(diao)電阻(zu)(zu)(zu)使亮度(du)控(kong)制電壓為7.9V，關(guan)機焊(han)(han)下可(ke)(ke)調(diao)電阻(zu)(zu)(zu)，測得其阻(zu)(zu)(zu)值為40kft.在步驟⑵、⑶中。如果調(diao)整可(ke)(ke)調(diao)電阻(zu)(zu)(zu)達不到所需(xu)電壓，就將(jiang)可(ke)(ke)調(diao)電阻(zu)(zu)(zu)由51kfl換成200M1后重試。

　　⑷一般(ban)來說，選(xuan)擇偏小的(de)(de)輸出電(dian)阻使調(diao)節范圍適當擴大為(wei)宜，這里(li)(li)選(xuan)R17=36kft.經測試亮度控制(zhi)電(dian)壓為(wei)7.3~8.IV，效果(guo)很理想。如果(guo)選(xuan)R17=33kft，效果(guo)也不(bu)錯。其它三個模擬(ni)量(liang)輸出電(dian)阻的(de)(de)選(xuan)擇方法與此相同，這里(li)(li)不(bu)再贅述。

　　從上(shang)(shang)面(mian)(mian)的(de)(de)介紹中不(bu)(bu)(bu)難發現(xian)這種方法有三(san)個優點：（1）不(bu)(bu)(bu)需(xu)對(dui)電(dian)(dian)(dian)(dian)(dian)路(lu)進(jin)行(xing)太多分析和了解。⑵需(xu)要(yao)調整電(dian)(dian)(dian)(dian)(dian)阻(zu)由12只(zhi)(zhi)變成(cheng)(cheng)4只(zhi)(zhi)，減少了工作(zuo)量(liang)。⑶調整精(jing)度(du)便(bian)于控(kong)制，有利于提高圖(tu)像(xiang)質量(liang)。必須說明的(de)(de)是，這里介紹的(de)(de)；1一(yi)般性的(de)(de)方法，在實際工作(zuo)中應靈活運(yun)用(yong)(yong)(yong)。例如(ru)，在對(dui)本例的(de)(de)音量(liang)控(kong)制電(dian)(dian)(dian)(dian)(dian)路(lu)進(jin)行(xing)連接時(shi)(shi)(shi)，可(ke)(ke)將(jiang)遙控(kong)板上(shang)(shang)的(de)(de)三(san)只(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)阻(zu)R11、R12、R13拔掉(diao)，將(jiang)電(dian)(dian)(dian)(dian)(dian)視機(ji)中的(de)(de)R302移到遙控(kong)板上(shang)(shang)R11的(de)(de)位置，如(ru)所(suo)示，則音量(liang)控(kong)制電(dian)(dian)(dian)(dian)(dian)壓(ya)為0~5.6V，效果不(bu)(bu)(bu)錯。對(dui)于控(kong)制電(dian)(dian)(dian)(dian)(dian)壓(ya)為0~12V的(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)，如(ru)夏普NC-2T的(de)(de)色度(du)和對(dui)比度(du)控(kong)制電(dian)(dian)(dian)(dian)(dian)路(lu)，可(ke)(ke)將(jiang)遙控(kong)板輸出(chu)端(duan)的(de)(de)上(shang)(shang)、下偏置電(dian)(dian)(dian)(dian)(dian)阻(zu)拔掉(diao)，將(jiang)輸出(chu)電(dian)(dian)(dian)(dian)(dian)阻(zu)換成(cheng)(cheng)l~2kft即可(ke)(ke)使用(yong)(yong)(yong)。這時(shi)(shi)(shi)輸出(chu)電(dian)(dian)(dian)(dian)(dian)阻(zu)僅起限流作(zuo)用(yong)(yong)(yong)，以(yi)保護遙控(kong)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)源只(zhi)(zhi)能處于間歇振蕩狀態。表現(xian)在電(dian)(dian)(dian)(dian)(dian)視屏幕(mu)上(shang)(shang)的(de)(de)故障(zhang)現(xian)象是：電(dian)(dian)(dian)(dian)(dian)視屏幕(mu)亮度(du)高時(shi)(shi)(shi)，光柵會不(bu)(bu)(bu)斷地收縮(suo)。或者當(dang)電(dian)(dian)(dian)(dian)(dian)視畫(hua)(hua)面(mian)(mian)較(jiao)暗(an)時(shi)(shi)(shi)，圖(tu)像(xiang)尚能穩(wen)定(ding)(ding)住(zhu)。當(dang)電(dian)(dian)(dian)(dian)(dian)視畫(hua)(hua)面(mian)(mian)較(jiao)亮時(shi)(shi)(shi)，就會出(chu)現(xian)“光柵不(bu)(bu)(bu)停地收縮(suo)――展開(kai)一(yi)收縮(suo)”。這時(shi)(shi)(shi)你測量(liang)+B115V電(dian)(dian)(dian)(dian)(dian)壓(ya)，在光柵收縮(suo)瞬間會降至(zhi)70V左右。該電(dian)(dian)(dian)(dian)(dian)視機(ji)在調機(ji)進(jin)行(xing)搜索(suo)(suo)時(shi)(shi)(shi)，搜索(suo)(suo)到的(de)(de)圖(tu)像(xiang)比較(jiao)暗(an)時(shi)(shi)(shi)，可(ke)(ke)以(yi)正常搜索(suo)(suo)并(bing)存儲。搜索(suo)(suo)到的(de)(de)圖(tu)像(xiang)較(jiao)亮時(shi)(shi)(shi)，光柵來(lai)回閃動，圖(tu)像(xiang)不(bu)(bu)(bu)穩(wen)定(ding)(ding)，或同步不(bu)(bu)(bu)良，電(dian)(dian)(dian)(dian)(dian)視頻道不(bu)(bu)(bu)能存儲。

                                                                                                                   本(ben)文摘(zhai)自(zi)于中(zhong)國(guo)鋰電網