功放機維修常用方法詳解

一、直觀檢查法

直觀檢查(cha)法是本(ben)著(zhu)先簡(jian)(jian)后繁的(de)原(yuan)則，通過(guo)眼看、耳聽、鼻聞、手(shou)摸(mo)等手(shou)段，對故(gu)(gu)(gu)障機(ji)進行大體的(de)檢查(cha)，以發現(xian)產生故(gu)(gu)(gu)障的(de)部(bu)位(wei)和原(yuan)因。此方法對處理一些(xie)簡(jian)(jian)單而(er)明顯的(de)故(gu)(gu)(gu)障十分有效。

用直觀檢(jian)查(cha)法(fa)檢(jian)修時(shi)，可(ke)先查(cha)看外部旋(xuan)鈕、開關(guan)及各信號線連(lian)接是否正確(que)，機(ji)內電路中(zhong)有無明顯燒毀(hui)、變色(se)、斷裂和(he)接觸不良的元(yuan)件與線路。若(ruo)未(wei)見(jian)異常(chang)，可(ke)通電試機(ji)。若(ruo)發(fa)現(xian)機(ji)內有冒煙、跳火，或聞到元(yuan)器件燒焦的糊(hu)味(wei)、聽到異常(chang)的響聲時(shi)，應(ying)立即(ji)切(qie)斷電源，并檢(jian)查(cha)其(qi)原因(yin)所(suo)在，以免擴(kuo)大(da)故障。

在檢(jian)修電子(zi)管放大器時，通(tong)過觀察電子(zi)管燈絲(si)是否(fou)(fou)發亮，可(ke)(ke)判斷(duan)燈絲(si)或其供電是否(fou)(fou)正常。另外，斷(duan)電后手摸可(ke)(ke)疑(yi)元件，根據該元件是否(fou)(fou)發燙可(ke)(ke)判斷(duan)它(ta)是否(fou)(fou)損(sun)壞。

二、萬用表測量法

檢修時，在確定了(le)故障(zhang)發生(sheng)的大致部(bu)位后，可用(yong)萬用(yong)表(biao)對故障(zhang)電(dian)路與元器件進行電(dian)壓、電(dian)流或電(dian)阻值的測量(liang)，再通(tong)過與正常工作時的數值相比(bi)較(jiao)，從而判斷出故障(zhang)所在。

其中，電(dian)(dian)壓測(ce)量法(fa)用來檢查電(dian)(dian)源各輸入(ru)輸出(chu)電(dian)(dian)壓及晶(jing)體(ti)管、電(dian)(dian)子(zi)管、集成電(dian)(dian)路(lu)(lu)等元(yuan)器(qi)件的工作電(dian)(dian)壓，根據電(dian)(dian)壓的有無及高低變(bian)化，來判(pan)斷(duan)故障(zhang)是在被測(ce)元(yuan)件本身，還是在其外圍元(yuan)件或供(gong)電(dian)(dian)電(dian)(dian)路(lu)(lu)。

電(dian)阻(zu)測量法用(yong)來測量各種(zhong)電(dian)子(zi)元件的直(zhi)流電(dian)阻(zu)值，看其有無開路(lu)、短路(lu)或性(xing)能變差，還可測量某一線路(lu)是否斷路(lu)。

電(dian)(dian)(dian)流(liu)測(ce)量法用來測(ce)量某—部分(fen)電(dian)(dian)(dian)路(lu)(lu)或(huo)電(dian)(dian)(dian)子元(yuan)件的(de)電(dian)(dian)(dian)流(liu)值(zhi)，推斷(duan)該(gai)電(dian)(dian)(dian)路(lu)(lu)或(huo)元(yuan)件本身有(you)無故障(zhang)。通常是把萬用表置于適當(dang)電(dian)(dian)(dian)流(liu)擋，將兩表筆串(chuan)接在電(dian)(dian)(dian)路(lu)(lu)中，根(gen)據(ju)表針指示(shi)或(huo)數字顯示(shi)值(zhi)讀出電(dian)(dian)(dian)流(liu)的(de)大(da)小。也(ye)可(ke)用電(dian)(dian)(dian)壓(ya)法測(ce)某電(dian)(dian)(dian)阻(zu)兩端(duan)的(de)電(dian)(dian)(dian)壓(ya)降(jiang)，然(ran)后根(gen)據(ju)歐姆(mu)定律(lv)計(ji)算(suan)出通過該(gai)電(dian)(dian)(dian)阻(zu)的(de)電(dian)(dian)(dian)流(liu)。

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三、信號干擾法

信(xin)(xin)號(hao)干擾法主要用于音頻模擬電路(lu)的(de)(de)檢(jian)修。將(jiang)人體(ti)感應信(xin)(xin)號(hao)、直(zhi)流斷(duan)續信(xin)(xin)號(hao)或信(xin)(xin)號(hao)發生(sheng)器(qi)的(de)(de)輸(shu)出信(xin)(xin)號(hao)從放大器(qi)某級電路(lu)的(de)(de)輸(shu)入端加入，根據揚聲器(qi)發聲的(de)(de)強弱(ruo)來判斷(duan)故障發生(sheng)的(de)(de)大致部位(wei)。

信(xin)號干擾法(fa)適用(yong)(yong)(yong)于查(cha)找(zhao)各單(dan)元(或各級)電(dian)(dian)(dian)路直流工作狀態正常但無聲(sheng)或聲(sheng)小的(de)故障，一般是從(cong)后(hou)(hou)(hou)級逐級向前檢(jian)查(cha)。應(ying)該(gai)注(zhu)意(yi)的(de)是：在(zai)檢(jian)修后(hou)(hou)(hou)級功率放大(da)(da)器(qi)(尤(you)其是分立元件放大(da)(da)器(qi))時，應(ying)將音(yin)量電(dian)(dian)(dian)位器(qi)關小，然后(hou)(hou)(hou)在(zai)音(yin)量電(dian)(dian)(dian)位器(qi)前加入(ru)(ru)干擾信(xin)號。若用(yong)(yong)(yong)信(xin)號干擾法(fa)檢(jian)查(cha)音(yin)量電(dian)(dian)(dian)位器(qi)以后(hou)(hou)(hou)的(de)放大(da)(da)電(dian)(dian)(dian)路，應(ying)將揚聲(sheng)器(qi)換(huan)成合適的(de)假負載，然后(hou)(hou)(hou)用(yong)(yong)(yong)直流斷續信(xin)號(如利用(yong)(yong)(yong)萬用(yong)(yong)(yong)表(biao)(biao)(biao)的(de)R×1擋，將紅表(biao)(biao)(biao)筆接地，黑(hei)表(biao)(biao)(biao)筆點觸各信(xin)號輸入(ru)(ru)端)去(qu)檢(jian)查(cha)。最好(hao)不要(yao)用(yong)(yong)(yong)人體(ti)感(gan)應(ying)信(xin)號，以免損壞功率管(guan)或揚聲(sheng)器(qi)。用(yong)(yong)(yong)人體(ti)感(gan)應(ying)法(fa)檢(jian)查(cha)電(dian)(dian)(dian)子(zi)管(guan)放大(da)(da)器(qi)時，應(ying)串入(ru)(ru)適當電(dian)(dian)(dian)容器(qi)，注(zhu)意(yi)安(an)全，以免觸電(dian)(dian)(dian)。

四、短路/斷路法

短(duan)路(lu)(lu)檢查法(fa)是將(jiang)某元(yuan)件(jian)、某電(dian)(dian)路(lu)(lu)直接(jie)短(duan)路(lu)(lu)或用電(dian)(dian)容短(duan)接(jie)，以快速判斷(duan)故(gu)障部位。如將(jiang)靜噪控制管的基(ji)極對地短(duan)路(lu)(lu)，看靜噪電(dian)(dian)路(lu)(lu)是否誤(wu)動作；將(jiang)卡(ka)拉OK或音響效果處理(li)電(dian)(dian)路(lu)(lu)的輸入端(duan)(duan)與(yu)輸出(chu)端(duan)(duan)短(duan)接(jie)，以判斷(duan)此電(dian)(dian)路(lu)(lu)有無故(gu)障；用一只電(dian)(dian)容將(jiang)某一級放大電(dian)(dian)路(lu)(lu)的輸入端(duan)(duan)與(yu)地(或輸出(chu)端(duan)(duan))之間短(duan)路(lu)(lu)，可(ke)以判斷(duan)出(chu)自激嘯叫、交流(liu)聲等(deng)故(gu)障是發(fa)生在(zai)本級電(dian)(dian)路(lu)(lu)，還是前級電(dian)(dian)路(lu)(lu)。

開(kai)路(lu)檢(jian)查法在(zai)檢(jian)查電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)路(lu)時(shi)尤為實(shi)用，如測(ce)量出(chu)某直(zhi)流(liu)輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)偏低(di)時(shi)，可將其負載電(dian)(dian)(dian)(dian)路(lu)斷開(kai)，若電(dian)(dian)(dian)(dian)壓(ya)(ya)恢復(fu)正常，說明(ming)負載電(dian)(dian)(dian)(dian)路(lu)中存在(zai)短路(lu)故障(zhang)。在(zai)懷疑(yi)某旁路(lu)、退(tui)耦(ou)電(dian)(dian)(dian)(dian)容漏電(dian)(dian)(dian)(dian)或穩壓(ya)(ya)二極管性(xing)能不良(liang)而(er)造成某點(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)偏低(di)時(shi)，可將可疑(yi)元件的(de)引腳與電(dian)(dian)(dian)(dian)路(lu)斷開(kai)，看該(gai)點(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)是否恢復(fu)正常。

膽機常見六大故障維修方法>>

五、加熱/冷卻法

有的機(ji)(ji)器在(zai)熱(re)機(ji)(ji)后(即工作(zuo)一段時(shi)間)才出現(xian)(xian)故障(zhang)(zhang)，檢修時(shi)可(ke)(ke)用電烙鐵或電吹(chui)風(feng)等熱(re)源對可(ke)(ke)疑元件加溫(wen)，使故障(zhang)(zhang)很快出現(xian)(xian)。在(zai)故障(zhang)(zhang)出現(xian)(xian)后，再用酒精棉球對可(ke)(ke)疑元件降溫(wen)，若故障(zhang)(zhang)又(you)消失，即可(ke)(ke)判斷是該元件熱(re)穩定性(xing)不良。

六、代換法

代換(huan)(huan)法是用正常的元(yuan)器件(jian)或電(dian)(dian)路(lu)(lu)板替換(huan)(huan)可疑的元(yuan)器件(jian)或電(dian)(dian)路(lu)(lu)板，以(yi)快速判斷故障部位和(he)元(yuan)件(jian)。對于型號不同但性能參數相同的元(yuan)器件(jian)，也(ye)可以(yi)互換(huan)(huan)使(shi)用。