開關電源是利用(yong)(yong)(yong)現代電(dian)力電(dian)子技術，控制開(kai)關晶(jing)體管開(kai)通和關斷的(de)時間比(bi)率，維持穩定(ding)輸出電(dian)壓的(de)一種(zhong)電(dian)源。廣泛運用(yong)(yong)(yong)在(zai)工(gong)業、軍事、科(ke)研(yan)、通訊、醫療及多(duo)種(zhong)家用(yong)(yong)(yong)電(dian)器中。開(kai)關電(dian)源的(de)發展(zhan)與應用(yong)(yong)(yong)在(zai)節約(yue)能(neng)源、節約(yue)資源及保護環境方面(mian)都具有重要(yao)的(de)意(yi)義。下面(mian)我(wo)們就來看看開(kai)關電(dian)源電(dian)路圖與維修技巧(qiao)。
開關電(dian)(dian)(dian)(dian)源的主要(yao)電(dian)(dian)(dian)(dian)路(lu)(lu)是由輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)磁(ci)干擾濾波器（EMI）、整(zheng)流(liu)濾波電(dian)(dian)(dian)(dian)路(lu)(lu)、功率變(bian)換電(dian)(dian)(dian)(dian)路(lu)(lu)、PWM控制(zhi)器電(dian)(dian)(dian)(dian)路(lu)(lu)、輸(shu)(shu)(shu)出(chu)整(zheng)流(liu)濾波電(dian)(dian)(dian)(dian)路(lu)(lu)組成。輔助電(dian)(dian)(dian)(dian)路(lu)(lu)有輸(shu)(shu)(shu)入過欠壓(ya)保(bao)護(hu)電(dian)(dian)(dian)(dian)路(lu)(lu)、輸(shu)(shu)(shu)出(chu)過欠壓(ya)保(bao)護(hu)電(dian)(dian)(dian)(dian)路(lu)(lu)、輸(shu)(shu)(shu)出(chu)過流(liu)保(bao)護(hu)電(dian)(dian)(dian)(dian)路(lu)(lu)、輸(shu)(shu)(shu)出(chu)短路(lu)(lu)保(bao)護(hu)電(dian)(dian)(dian)(dian)路(lu)(lu)等。
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通電后(hou)觀察電源是否有燒(shao)保(bao)險及(ji)個別(bie)元件(jian)冒煙(yan)等現象，若有要及(ji)時(shi)切斷供(gong)電進(jin)行檢修。
測量高壓(ya)濾(lv)波電容兩(liang)端有(you)無(wu)300伏輸出，若無(wu)應重點查整流二極(ji)管、濾(lv)波電容等(deng)。
測量高頻變壓器次級線圈(quan)有(you)無輸出，若無應(ying)重點(dian)查開關管是否(fou)損壞，是否(fou)起振(zhen)，保護電路是否(fou)動作(zuo)等(deng)，若有(you)則應(ying)重點(dian)檢(jian)查各(ge)輸出側(ce)的整流(liu)二極(ji)管、濾波電容、三通穩(wen)壓管等(deng)。
如(ru)果電(dian)源啟動(dong)一(yi)下就停止，則(ze)該電(dian)源處于(yu)保(bao)(bao)護(hu)狀態下，可直(zhi)接測量(liang)PWM芯片保(bao)(bao)護(hu)輸入腳(jiao)的電(dian)壓(ya)，如(ru)果電(dian)壓(ya)超出規定值，則(ze)說(shuo)明電(dian)源處于(yu)保(bao)(bao)護(hu)狀態下，應(ying)重(zhong)點(dian)檢查(cha)產生保(bao)(bao)護(hu)的原因。
總之，開關電(dian)(dian)源(yuan)(yuan)電(dian)(dian)路有(you)易(yi)有(you)難，功(gong)率有(you)大有(you)小(xiao)，輸出電(dian)(dian)壓多種多樣。只要按照上(shang)述維修技巧，多動(dong)手進行(xing)開關電(dian)(dian)源(yuan)(yuan)的維修，就能(neng)迅速地(di)排除開關電(dian)(dian)源(yuan)(yuan)故障，達到事半功(gong)倍的效果。
看：打開電源的外殼(ke)，檢查(cha)保險絲是否熔斷，再觀(guan)察(cha)電源的內(nei)部情況，如果發現電源的PCB板上有(you)燒(shao)焦處或元件破裂，則應重點(dian)檢查(cha)此處元件及(ji)相關(guan)電路元件。
聞(wen)：聞(wen)一下電(dian)源內(nei)部(bu)是否有糊味，檢查是否有燒(shao)焦的元器件。
問：問一下(xia)電(dian)源(yuan)(yuan)損壞(huai)的(de)經過，是(shi)否對(dui)電(dian)源(yuan)(yuan)進(jin)行(xing)違規操作。
量(liang)：沒通電(dian)(dian)(dian)(dian)(dian)前，用(yong)(yong)萬(wan)用(yong)(yong)表量(liang)一下(xia)高壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)容兩端的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)先。如(ru)果是(shi)開關(guan)電(dian)(dian)(dian)(dian)(dian)源不起(qi)振或開關(guan)管開路引起(qi)的(de)(de)(de)(de)故(gu)障，則(ze)大多數情(qing)況下(xia)，高壓(ya)(ya)濾波電(dian)(dian)(dian)(dian)(dian)容兩端的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)未泄放(fang)悼，用(yong)(yong)萬(wan)用(yong)(yong)表測(ce)量(liang)AC電(dian)(dian)(dian)(dian)(dian)源線(xian)兩端的(de)(de)(de)(de)正反向電(dian)(dian)(dian)(dian)(dian)阻(zu)及電(dian)(dian)(dian)(dian)(dian)容器(qi)充電(dian)(dian)(dian)(dian)(dian)情(qing)況，電(dian)(dian)(dian)(dian)(dian)阻(zu)值(zhi)不應(ying)過低，否則(ze)電(dian)(dian)(dian)(dian)(dian)源內部可能(neng)存在短路。電(dian)(dian)(dian)(dian)(dian)容器(qi)應(ying)能(neng)充放(fang)電(dian)(dian)(dian)(dian)(dian)。脫開負載，分(fen)別測(ce)量(liang)各組輸出端的(de)(de)(de)(de)對地(di)電(dian)(dian)(dian)(dian)(dian)阻(zu)，正常時，表針(zhen)應(ying)有(you)電(dian)(dian)(dian)(dian)(dian)容器(qi)充放(fang)電(dian)(dian)(dian)(dian)(dian)擺(bai)動，最后指示的(de)(de)(de)(de)應(ying)為(wei)該路的(de)(de)(de)(de)泄放(fang)電(dian)(dian)(dian)(dian)(dian)阻(zu)的(de)(de)(de)(de)阻(zu)值(zhi)。
一般(ban)情(qing)況下(xia)，保險絲熔斷(duan)說明開(kai)關電(dian)(dian)(dian)源(yuan)的(de)內部電(dian)(dian)(dian)路(lu)存在(zai)短路(lu)或過流的(de)故障。由于開(kai)關電(dian)(dian)(dian)源(yuan)工(gong)作在(zai)高(gao)(gao)電(dian)(dian)(dian)壓(ya)，大電(dian)(dian)(dian)流的(de)狀態(tai)(tai)下(xia)，直(zhi)流濾(lv)波和(he)變(bian)換(huan)振蕩電(dian)(dian)(dian)路(lu)在(zai)高(gao)(gao)壓(ya)狀態(tai)(tai)工(gong)作時間太長，電(dian)(dian)(dian)壓(ya)變(bian)化相對(dui)大。電(dian)(dian)(dian)網電(dian)(dian)(dian)壓(ya)的(de)波動，浪涌都會引(yin)起(qi)電(dian)(dian)(dian)源(yuan)內電(dian)(dian)(dian)流瞬間增大而使保險絲熔斷(duan)。重(zhong)點應檢查電(dian)(dian)(dian)源(yuan)輸入端(duan)的(de)整流二極管，高(gao)(gao)壓(ya)濾(lv)波電(dian)(dian)(dian)解電(dian)(dian)(dian)容，開(kai)關功率管，UC3842本身及外圍元(yuan)器(qi)件(jian)等(deng)(deng)。檢查一下(xia)這(zhe)些元(yuan)器(qi)件(jian)有無擊穿，開(kai)路(lu)，損壞，燒焦，炸裂(lie)等(deng)(deng)現象。
維修方法：首(shou)先(xian)仔細(xi)查(cha)(cha)看(kan)電(dian)(dian)(dian)路(lu)板(ban)上面的(de)各個元(yuan)件(jian)，看(kan)是(shi)(shi)否(fou)(fou)在(zai)這些元(yuan)件(jian)的(de)外表(biao)有(you)(you)(you)沒有(you)(you)(you)被燒(shao)糊,有(you)(you)(you)沒有(you)(you)(you)電(dian)(dian)(dian)解液(ye)溢(yi)出，聞一聞有(you)(you)(you)沒有(you)(you)(you)異味。經(jing)看(kan)，聞之后(hou)，再(zai)用(yong)萬用(yong)表(biao)進行(xing)(xing)檢查(cha)(cha)。首(shou)先(xian)測量(liang)(liang)一下(xia)(xia)電(dian)(dian)(dian)源(yuan)輸入(ru)端的(de)電(dian)(dian)(dian)阻(zu)值，若小(xiao)于(yu)200K，則說(shuo)明后(hou)端有(you)(you)(you)局部(bu)短路(lu)現象，然后(hou)分別(bie)測量(liang)(liang)四只整流二極管(guan)(guan)正，反(fan)向電(dian)(dian)(dian)阻(zu)和兩個限流電(dian)(dian)(dian)阻(zu)的(de)阻(zu)值，看(kan)其有(you)(you)(you)無(wu)短路(lu)或燒(shao)壞(huai)；然后(hou)再(zai)測量(liang)(liang)一下(xia)(xia)電(dian)(dian)(dian)源(yuan)濾波電(dian)(dian)(dian)容是(shi)(shi)否(fou)(fou)能進行(xing)(xing)正常充(chong)放電(dian)(dian)(dian)，再(zai)就測量(liang)(liang)一下(xia)(xia)開關(guan)功率管(guan)(guan)是(shi)(shi)否(fou)(fou)擊穿(chuan)損(sun)壞(huai)，以(yi)及UC3842本身，及周(zhou)圍(wei)元(yuan)件(jian)是(shi)(shi)否(fou)(fou)擊穿(chuan)，燒(shao)壞(huai)等。需要(yao)說(shuo)明的(de)一點是(shi)(shi)：因是(shi)(shi)在(zai)路(lu)測量(liang)(liang)，有(you)(you)(you)可能會使測量(liang)(liang)結果有(you)(you)(you)誤(wu)，造成(cheng)誤(wu)判。因此必要(yao)時可把元(yuan)器(qi)件(jian)焊下(xia)(xia)來(lai)再(zai)進行(xing)(xing)測量(liang)(liang)。如果仍然沒有(you)(you)(you)上述情況則測量(liang)(liang)一下(xia)(xia)輸入(ru)電(dian)(dian)(dian)源(yuan)線及輸出電(dian)(dian)(dian)源(yuan)線是(shi)(shi)否(fou)(fou)內部(bu)短路(lu)。一般情況下(xia)(xia)，熔(rong)斷(duan)器(qi)熔(rong)斷(duan)故障，整流二極管(guan)(guan)，電(dian)(dian)(dian)源(yuan)濾波電(dian)(dian)(dian)容，開關(guan)功率管(guan)(guan)，UC3842是(shi)(shi)易損(sun)件(jian)，損(sun)壞(huai)的(de)概率可達95%以(yi)上，一般著重(zhong)檢查(cha)(cha)一下(xia)(xia)這些元(yuan)器(qi)件(jian)，就可很容易排除(chu)此類(lei)故障。
如果保(bao)險絲是(shi)完(wan)好的，在有負載的情(qing)況下，各級直(zhi)流電(dian)壓無輸出(chu)。這種情(qing)況主要是(shi)以下原(yuan)因(yin)造(zao)成的：電(dian)源(yuan)中(zhong)出(chu)現開(kai)路，短路現象(xiang)，過壓，過流保(bao)護電(dian)路出(chu)現故障(zhang)，振蕩電(dian)路沒有工(gong)作(zuo)，電(dian)源(yuan)負載過重，高(gao)頻整流濾波電(dian)路中(zhong)整流二極管被擊穿，濾波電(dian)容(rong)漏電(dian)等。
維修方法：首先，用萬(wan)用表測(ce)量一(yi)下(xia)高(gao)頻(pin)(pin)變壓(ya)(ya)器(qi)(qi)次(ci)級的(de)(de)各個元(yuan)器(qi)(qi)件是(shi)否(fou)有(you)損壞。在(zai)排(pai)除了高(gao)頻(pin)(pin)整流(liu)二(er)極(ji)管擊穿、負載短路的(de)(de)情況(kuang)后，然(ran)后在(zai)測(ce)量各輸(shu)出(chu)端的(de)(de)直流(liu)電(dian)(dian)(dian)壓(ya)(ya)，如(ru)果(guo)這(zhe)時輸(shu)出(chu)仍為零，則可以肯定是(shi)電(dian)(dian)(dian)源的(de)(de)控(kong)制電(dian)(dian)(dian)路出(chu)了故(gu)(gu)障。控(kong)制電(dian)(dian)(dian)路的(de)(de)兩(liang)部分是(shi)集(ji)成開(kai)(kai)關(guan)電(dian)(dian)(dian)源控(kong)制器(qi)(qi)和過壓(ya)(ya)保護電(dian)(dian)(dian)路。最后用萬(wan)用表靜態測(ce)量高(gao)頻(pin)(pin)濾波電(dian)(dian)(dian)路中(zhong)整流(liu)二(er)極(ji)管及低壓(ya)(ya)濾波電(dian)(dian)(dian)容是(shi)否(fou)損壞。如(ru)果(guo)確實相關(guan)的(de)(de)元(yuan)件損壞，在(zai)更換(huan)好新的(de)(de)完好的(de)(de)元(yuan)件后，開(kai)(kai)機測(ce)試，一(yi)般故(gu)(gu)障即可排(pai)除。需要說明的(de)(de)是(shi)：電(dian)(dian)(dian)源輸(shu)出(chu)線斷線或(huo)開(kai)(kai)焊(han)，虛焊(han)也會造成這(zhe)種故(gu)(gu)障。在(zai)維修時應注意這(zhe)一(yi)點。
電源負(fu)載(zai)能力(li)差(cha)是一個常見的(de)故障，一般都是出現在(zai)老(lao)式或是工作時間(jian)長的(de)電源中，主要原因(yin)是各元器件老(lao)化，開關管(guan)的(de)工作不穩定，沒有(you)(you)及時進行散熱等。此外還有(you)(you)穩壓二極(ji)管(guan)發熱漏(lou)電，整流二極(ji)管(guan)損壞等。
維修方法：用萬用表著重檢(jian)(jian)查一(yi)下穩壓(ya)(ya)二極管，高壓(ya)(ya)濾(lv)波電容，限流電阻有無(wu)變(bian)質等再仔細(xi)檢(jian)(jian)查一(yi)下電路板上的所(suo)有焊點(dian)是否開焊，虛接等。把開焊的焊點(dian)重新焊牢(lao)，更換變(bian)質的元器件(jian)，一(yi)般故(gu)障(zhang)即(ji)可排除。
這種(zhong)現(xian)象說明開關電源未工作(zuo)，或者工作(zuo)后進(jin)入了(le)保護(hu)狀(zhuang)態。
維修方法(fa)：首先應(ying)判斷一(yi)下開(kai)關電(dian)(dian)源(yuan)的主控芯(xin)片UC3842是(shi)(shi)否處在工作狀態或已經損壞(huai)(huai)。判斷方法(fa)是(shi)(shi)這樣的：加電(dian)(dian)測UC3842的第(di)(di)7腳(jiao)(jiao)(jiao)對地電(dian)(dian)壓，若(ruo)測第(di)(di)8腳(jiao)(jiao)(jiao)有(you)+5V電(dian)(dian)壓，1，2，4，6腳(jiao)(jiao)(jiao)也(ye)有(you)不(bu)(bu)(bu)同的電(dian)(dian)壓，則(ze)說明電(dian)(dian)路已起振，UC3842基本正(zheng)(zheng)常；若(ruo)7腳(jiao)(jiao)(jiao)電(dian)(dian)壓低，其(qi)余管(guan)腳(jiao)(jiao)(jiao)無電(dian)(dian)壓或不(bu)(bu)(bu)波動，則(ze)UC3842已損壞(huai)(huai)。UC3842芯(xin)片損壞(huai)(huai)最常見的是(shi)(shi)6，7腳(jiao)(jiao)(jiao)對地擊(ji)穿，5，7腳(jiao)(jiao)(jiao)對地擊(ji)穿和1，7腳(jiao)(jiao)(jiao)對地擊(ji)穿。如果(guo)這幾只腳(jiao)(jiao)(jiao)都為擊(ji)穿，而開(kai)關電(dian)(dian)源(yuan)還是(shi)(shi)不(bu)(bu)(bu)能正(zheng)(zheng)常啟動，則(ze)UC3842必壞(huai)(huai)，應(ying)直接(jie)(jie)更換。若(ruo)判斷芯(xin)片未壞(huai)(huai)，則(ze)就著(zhu)重檢查開(kai)關功率管(guan)的柵極（G極）的限流電(dian)(dian)阻是(shi)(shi)否開(kai)焊，虛接(jie)(jie)，變(bian)值(zhi)，變(bian)質以及開(kai)關功率管(guan)本身是(shi)(shi)否性能不(bu)(bu)(bu)良(liang)(liang)。除此之外，電(dian)(dian)源(yuan)輸(shu)出(chu)線也(ye)有(you)可能斷線或接(jie)(jie)觸不(bu)(bu)(bu)良(liang)(liang)也(ye)會造成這種故障。因此在維修時也(ye)應(ying)注意檢查一(yi)下。
這種(zhong)故障往往來自于穩壓(ya)取(qu)樣和穩壓(ya)控(kong)制電(dian)(dian)路出(chu)現故障所(suo)致。在開關(guan)電(dian)(dian)源(yuan)中，直(zhi)流(liu)輸(shu)出(chu)、取(qu)樣電(dian)(dian)阻、誤差取(qu)樣放(fang)大器（如LM324，LM358等）、光耦合(he)器（PC817）、電(dian)(dian)源(yuan)控(kong)制芯片（UC3842）等電(dian)(dian)路共(gong)同(tong)構成了一個閉合(he)的控(kong)制環路，任何(he)一處出(chu)問題都會導致輸(shu)出(chu)電(dian)(dian)壓(ya)升高。
維修(xiu)方法：由于開關電(dian)(dian)源(yuan)中(zhong)有(you)過壓(ya)(ya)(ya)保(bao)護(hu)電(dian)(dian)路，輸出(chu)電(dian)(dian)壓(ya)(ya)(ya)過高首先會使(shi)過壓(ya)(ya)(ya)保(bao)護(hu)電(dian)(dian)路動作。因此(ci)對(dui)于這種故障的(de)維修(xiu)，我們可以通過斷開過壓(ya)(ya)(ya)保(bao)護(hu)電(dian)(dian)路，使(shi)過壓(ya)(ya)(ya)保(bao)護(hu)電(dian)(dian)路不起作用，在這時，測量(liang)開機瞬間(jian)的(de)電(dian)(dian)源(yuan)主電(dian)(dian)壓(ya)(ya)(ya)。如果測量(liang)值(zhi)比(bi)正常值(zhi)高出(chu)IV以上，說明輸出(chu)電(dian)(dian)壓(ya)(ya)(ya)過高。我們應著重檢查取樣電(dian)(dian)阻是否變(bian)值(zhi)或損(sun)壞(huai)，精(jing)密(mi)(mi)(mi)穩壓(ya)(ya)(ya)放大器（TL431）或光(guang)耦合器（PC817）性能(neng)不良，變(bian)質(zhi)或損(sun)壞(huai)；其中(zhong)精(jing)密(mi)(mi)(mi)穩壓(ya)(ya)(ya)放大器（TL431）極易損(sun)壞(huai)，我們可用下述方法對(dui)精(jing)密(mi)(mi)(mi)穩壓(ya)(ya)(ya)放大器（TL431）作出(chu)好壞(huai)的(de)判別：將TL431的(de)參考端（Ref）與(yu)它的(de)陰極（Cathode）相連，串10k的(de)電(dian)(dian)阻，接(jie)入5V電(dian)(dian)壓(ya)(ya)(ya)，若陽(yang)極（Anode）與(yu)陰極之間(jian)為(wei)(wei)2、5V，并且等待片刻還仍然為(wei)(wei)2、5V，則為(wei)(wei)好管，否則為(wei)(wei)壞(huai)管。
對于這種故障現象，根據維修(xiu)經(jing)驗可知，除穩(wen)壓(ya)控制電(dian)路(lu)會引起(qi)輸出(chu)電(dian)壓(ya)過低外，還有(you)一些原因會引起(qi)輸出(chu)電(dian)壓(ya)過低，主要有(you)以下幾點(dian):
① 開(kai)(kai)關(guan)電(dian)源負載(zai)(zai)有(you)短路(lu)故障(zhang)。此時，應斷(duan)開(kai)(kai)開(kai)(kai)關(guan)電(dian)源電(dian)路(lu)的(de)所有(you)負載(zai)(zai)，以區分是(shi)開(kai)(kai)關(guan)電(dian)源電(dian)路(lu)還是(shi)負載(zai)(zai)電(dian)路(lu)有(you)故障(zhang)。若斷(duan)開(kai)(kai)負載(zai)(zai)電(dian)路(lu)電(dian)壓輸出正(zheng)常，說明是(shi)負載(zai)(zai)過重；若仍不正(zheng)常，說明開(kai)(kai)關(guan)電(dian)源電(dian)路(lu)有(you)故障(zhang)。
② 輸出電(dian)壓(ya)端整流二極管、濾(lv)波電(dian)容失(shi)效等，可以通過代換法進行判斷。
③ 開關(guan)功率管的性能(neng)(neng)下(xia)降，必然導(dao)致(zhi)開關(guan)管不能(neng)(neng)正(zheng)常導(dao)通，使電(dian)源的內阻增加(jia)，帶負載能(neng)(neng)力下(xia)降。
④ 開(kai)關功率管的(de)(de)(de)源極（S極），通(tong)常接一個阻(zu)值(zhi)很小，但功率很大的(de)(de)(de)電(dian)(dian)(dian)阻(zu)，作(zuo)為過(guo)流保(bao)護檢測電(dian)(dian)(dian)阻(zu)，此電(dian)(dian)(dian)阻(zu)的(de)(de)(de)阻(zu)值(zhi)一般在0.2到0.8之間。此電(dian)(dian)(dian)阻(zu)如變值(zhi)或(huo)開(kai)焊，接觸不良也會(hui)造(zao)成輸出(chu)電(dian)(dian)(dian)壓過(guo)低(di)的(de)(de)(de)故障。
高(gao)頻變(bian)壓(ya)器不(bu)良，不(bu)但造(zao)(zao)成輸出電壓(ya)下降，還會(hui)造(zao)(zao)成開(kai)關功率管激勵不(bu)足從(cong)而屢(lv)損開(kai)關管。
⑤ 高壓直流濾波電(dian)容不良，造成(cheng)電(dian)源帶負載能力(li)差，一接負載輸出電(dian)壓便下降。
⑥ 電源輸出線接(jie)觸不良(liang)，有一(yi)定的接(jie)觸電阻，造成輸出電壓過低。
⑦ 電(dian)(dian)網電(dian)(dian)壓(ya)是否(fou)過低(di)。雖然開關電(dian)(dian)源(yuan)在低(di)壓(ya)下仍然可以輸出(chu)額(e)定(ding)的電(dian)(dian)壓(ya)值，但(dan)當電(dian)(dian)網電(dian)(dian)壓(ya)低(di)于(yu)開關電(dian)(dian)源(yuan)的最低(di)電(dian)(dian)壓(ya)限定(ding)值時，也(ye)會使輸出(chu)電(dian)(dian)壓(ya)過低(di)。
維(wei)修方法：對于這種故(gu)障(zhang)我們可以根據以上故(gu)障(zhang)原因(yin)，來逐(zhu)一(yi)進(jin)行(xing)排查。但在實(shi)際維(wei)修時(shi)(shi)，可根據實(shi)際情況來進(jin)行(xing)排查，不(bu)(bu)一(yi)定要逐(zhu)一(yi)排查。首先用(yong)萬(wan)用(yong)表檢(jian)查一(yi)下(xia)(xia)高(gao)壓(ya)(ya)直流濾波電(dian)(dian)(dian)容(rong)是否(fou)變(bian)(bian)質，容(rong)量(liang)是否(fou)下(xia)(xia)降(jiang)，能(neng)否(fou)正常(chang)充放電(dian)(dian)(dian)。如(ru)無以上現(xian)象，則測量(liang)一(yi)下(xia)(xia)開關功(gong)率(lv)管的(de)(de)(de)(de)(de)柵極（G極）的(de)(de)(de)(de)(de)限流電(dian)(dian)(dian)阻以及(ji)源(yuan)(yuan)極（S極）的(de)(de)(de)(de)(de)過流保護(hu)檢(jian)測電(dian)(dian)(dian)阻是否(fou)變(bian)(bian)值，變(bian)(bian)質或(huo)(huo)開焊，接(jie)觸不(bu)(bu)良(liang)。經判別(bie)后，若無問題，我們就檢(jian)查一(yi)下(xia)(xia)高(gao)頻(pin)(pin)變(bian)(bian)壓(ya)(ya)器(qi)的(de)(de)(de)(de)(de)鐵芯(xin)(xin)是否(fou)完好(hao)無損(sun)。因(yin)在日(ri)常(chang)生活使用(yong)中，不(bu)(bu)可避免(mian)的(de)(de)(de)(de)(de)重摔(shuai)或(huo)(huo)重幢(chuang)，使高(gao)頻(pin)(pin)變(bian)(bian)壓(ya)(ya)器(qi)的(de)(de)(de)(de)(de)鐵芯(xin)(xin)損(sun)壞。使高(gao)頻(pin)(pin)變(bian)(bian)壓(ya)(ya)器(qi)的(de)(de)(de)(de)(de)磁通量(liang)，磁感應強度，以及(ji)磁路等都(dou)會受(shou)到很(hen)(hen)大(da)的(de)(de)(de)(de)(de)影(ying)響，造成傳(chuan)輸的(de)(de)(de)(de)(de)效率(lv)，能(neng)量(liang)將會大(da)打折扣。由于高(gao)頻(pin)(pin)變(bian)(bian)壓(ya)(ya)器(qi)為了減小渦流，增大(da)高(gao)頻(pin)(pin)交流電(dian)(dian)(dian)的(de)(de)(de)(de)(de)傳(chuan)輸效率(lv)，它的(de)(de)(de)(de)(de)鐵芯(xin)(xin)是用(yong)軟磁鐵氧(yang)體制(zhi)作(zuo)而成的(de)(de)(de)(de)(de)。這種磁性材料具有(you)高(gao)的(de)(de)(de)(de)(de)導(dao)磁率(lv)，但質脆(cui)，易碎。因(yin)此(ci)(ci)它的(de)(de)(de)(de)(de)損(sun)壞率(lv)也是很(hen)(hen)高(gao)的(de)(de)(de)(de)(de)。因(yin)此(ci)(ci)在維(wei)修時(shi)(shi)千(qian)萬(wan)不(bu)(bu)要忘了檢(jian)查此(ci)(ci)處，以免(mian)走彎(wan)路。除(chu)此(ci)(ci)之外還有(you)可能(neng)就是輸出濾波電(dian)(dian)(dian)容(rong)容(rong)量(liang)降(jiang)低(di)，甚(shen)至失容(rong)或(huo)(huo)開焊，虛(xu)(xu)接(jie)；電(dian)(dian)(dian)源(yuan)(yuan)輸出限流電(dian)(dian)(dian)阻變(bian)(bian)值或(huo)(huo)虛(xu)(xu)接(jie)，電(dian)(dian)(dian)源(yuan)(yuan)輸出線虛(xu)(xu)接(jie)等。在實(shi)際維(wei)修時(shi)(shi)，這些因(yin)素(su)都(dou)不(bu)(bu)要放過，都(dou)應檢(jian)查一(yi)下(xia)(xia)，以保證萬(wan)無一(yi)失。
這種故(gu)障(zhang)原因主要是由于控制(zhi)風扇的三(san)極(ji)管（8550或(huo)8050）損(sun)壞，或(huo)者風扇本身(shen)損(sun)壞或(huo)風葉(xie)被雜物(wu)卡(ka)住。但有些開(kai)關(guan)電源中采用的是智能散(san)熱，對于采用這種方(fang)式散(san)熱的開(kai)關(guan)電源，熱敏電阻損(sun)壞的概率是很大的。
維修方法：首先(xian)用(yong)萬用(yong)表測(ce)量一下控制風扇的三極管是否(fou)損壞(huai)(huai)，若測(ce)得(de)此(ci)管未損壞(huai)(huai)那(nei)就有可(ke)能是風扇本身損壞(huai)(huai)。可(ke)以把(ba)風扇從電(dian)(dian)路板上拔下來(lai)，另外接(jie)上一個(ge)12V的直流(liu)電(dian)(dian)（注意(yi)(yi)正負(fu)極），看是否(fou)轉動(dong)，并看有無異物卡住。若擺動(dong)幾下風扇的電(dian)(dian)線，風扇就轉動(dong)，則(ze)說(shuo)明電(dian)(dian)線內部有斷線或接(jie)頭(tou)接(jie)觸不良(liang)(liang)。若仍不轉動(dong)，則(ze)風扇必壞(huai)(huai)。對于采用(yong)智能散熱的開關電(dian)(dian)源來(lai)說(shuo)，除按上述檢查外，還應(ying)檢查一下熱敏(min)電(dian)(dian)阻是否(fou)不良(liang)(liang)或損壞(huai)(huai)，開焊等。但要注意(yi)(yi)此(ci)熱敏(min)電(dian)(dian)阻為負(fu)溫度(du)系數(shu)的熱敏(min)電(dian)(dian)阻，更換時應(ying)注意(yi)(yi)。
