ABBDCSAC700FCPU模块：CD722FAX721FABBDCSAC700FCPU模块：CD722FAX721FABBDCSAC700FCPU模块：CD722FAX721F一台变频器，开关电源出现间歇振荡现象，操作显示面板也时亮时熄。此为开关电源负载过重或存在短路状态的典型故障，负载异常引发了开关电源电流检测电路的保护动作，使开关电源处于间歇振荡状态。用逐路脱开负载电路的方法，排查短路故障是出在哪路负载电路，或停电后，测各路供电电源的输出端，是否有阻值变小或短路现象。测量+5V电源两端，呈现7.8Ω的小电阻值，而正常的电路阻值约为数百Ω。判断+5V负载电路有短路现象，将+5V负载电路脱开后，开关电源有了稳定输出，说明故障就在+5V负载电路。+5V供电电源由排线端子去了CPU主板，供CPU芯片及外围电路，电路范围比较广，CPU主板上+5V供电的集成电路比较多，达二十几片，用常规排除法检查短路故障的，须将各片IC电路的+5V供电脚挑开，配合电源输出端电阻值的检测，当挑开某片IC供电脚，电源输出端7.8Ω的小阻值变为正常的电阻值后，说明该片IC即存在短路故障，当然测量挑开IC的供电脚，检测其供电引脚的电阻值也是一样。无法预测需要挑开多少片IC后，才能找到故障IC。CPU主板元件焊接的“精致程度”已艰接近于手机的线路板，IC电路全为贴片元件，将IC引脚的铜箔条说成比头发丝还细，甚至于都不算是夸张。手底一不小心，挑掉铜箔条的话，想接起来都比较困难，挨片挑，这个法子也太笨了。由于变频器的开关电源本身负载能力有限，接于故障电路时会引发过流保护，使开关电源停止输出。故采用外接容量较大的+5V电源，串接5Ω5W限流电阻接到CPU主板上，通电几分钟后，用手触摸CPU主板上的IC芯片，哪片烫手，有异常温升，即是哪片IC已经坏掉了。这个法还真灵，挑开两片有异常温升的IC供电引脚，测其引脚电阻，均在十几Ω左右。此时再测+5V电源输出端，已经是数百Ω的正常阻值了。这是个好法子，算是将错就错或将计就计或顺势而为，利用外接+5V供电，既对好的IC没什么危害，又使坏IC持续升温，暴露在我手指的“测温仪”下。特别适宜于检测CPU主板上出现的IC短路故障。P0922SZP0922TCP0922TEP0922THP0922TLP0922TVP0922UAP0922UDP0922UGP0922UJP0922UKP0922ULP0922UMP0922UNP0922UPP0922UQP0922URP0922USP0922UTP0922UUP0922UVP0922UWP0922UXP0922VCP0922VSP0922VTP0922VUP0922VVP0922VWP0922WEP0922WFP0922WKP0922WNP0922WPP0922WQP0922WRP0922WSP0922WTP0922WUP0922WWP0922WZP0922XQP0922XRP0922XSP0922XTP0922XUP0922XVP0922XWP0922XXP0922XYP0922YAP0922YCP0922YHP0922YJP0922YKP0922YUP0922ZAP0922ZBP0922ZCP0922ZGP0922ZHP0922ZJP0922ZLP0922ZMP0922ZNP0922ZPP0922ZTP0922ZUP0922ZVP0922ZWP0922ZZP0923ACP0923AFP0923AGP0923AHP0923AKP0923ALP0923ANP0923APP0923ATP0923AXP0923BQP0923BRP0923BSP0923BTP0923BUP0923BVP0923BWP0923BXP0923BYP0923CAP0923CBP0923CCP0923CDP0923DAP0923DBP0923DCP0923DDP0923DGP0923DHP0923DKP0923DNP0923DPP0923DRP0923DSP0923DUP0923DVP0923DWP0923DYP0923DZP0923FBP0923FQP0923FSP0923FTP0923GFP0923GGP0923GLP0923GMP0923GNP0923GPP0923GQP0923GRP0923GTP0923GWP0923GXP0923GZP0923HMP0923HNP0923HPP0923HQP0923HRP0923HTP0923HUP0923HVP0923HXP0923JAP0923JDP0923JGP0923JKP0923JNP0923JVP0923JWP0923JXP0923JYP0923JZP0923KAP0923KDP0923KLP0923KPP0923KSP0923KVP0923LHP0923LLP0923LNP0923LRP0923LUP0923LVP0923LWP0923LXP0923LYP0923MAP0923MBP0923MCP0923MDP0923MEP0923MFP0923MGP0923MHP0923MMP0923MNP0923MPP0923MRP0923MXP0923MYP0923MZP0923NEP0923NFP0923NGP0923NLP0923NNP0923NPP0923NSP0923NTP0923NUP0923PFP0923PGP0923PHP0923PJP0923PKP0923PLP0923PMP0923PNP0923PPP0923PQP0923PRP0923PSP0923PTP0923QFP0923QGP0923QLP0923QMP0923QSP0923QTP0923QUP0923QVP0923QWP0923QXP0923QYP0923VAP0923VDP0923VEP0923VFP0923VJP0923VRP0923VSP0923VTP0923VVP0923ZBP0923ZCP0923ZDP0923ZEP0923ZFP0923ZGP0923ZHP0924DTP0924EAP0924EBP0924ECP0924EDP0924JHP0926AHP0926BEP0926CAP0926CBP0926CCP0926CDP0926CEP0926CFP0926CMP0926CNP0926CPP0926DFP0926DJP0926DPP0926DSP0926DVP0926DZP0926EAP0926EKP0926ELP0926EQP0926GGP0926GHP0926GJP0926GQP0926GRP0926GSP0926GUP0926GVP0926GWP0926GXP0926HCP0926HFP0926HJP0926HMP0926HQP0926HTP0926HWP0926HZP0926JCP0926JFP0926JJP0926JMP0926KEP0926KHP0926KKP0926KLP0926KMP0926KNP0926KPP0926KQP0926KRP0926KSP0926KTP0926KWP0926KZP0926LCP0926MXP0926MYP0926MZP0926NKP0926NLP0926NMP0926NNP0926NPP0926NQP0926NSP0926PAP0926PSP0926PTP0926QLP0926QMP0926QNP0926QPP0926QSP0926QTP0926QVP0926QWP0926QXP0926RVP0926SPP0926SQP0926SZP0926TDP0926THP0926TJP0926TKP0926TLP0926TMP0926TNP0926TPP0926TQP0926TRP0926VYP0926WGP0926WHP0926WJP0926WKP0926WLP0926WMP0926WNP0926WPP0926WQP0926XAP0926XBP0926XEP0926XMP0926ZNP0926ZPP0926ZYP0926ZZP0927AHP0927AJP0927BAP0927BBP0927BCP0927BDP0927BGP0927BHP0930ASP0930AUP0930CAP0930CBP0930CCP0930CDP0930CEP0930CFP0930CGP0930CHP0930DAP0930DBP0930DCP0930DDP0930DEP0930DFP0930DGP0930DHP0930DMP0930DNP0930DPP0930DRP0930DSP0930DTP0930DUP0930DVP0930DWP0930DXP0930DYP0930DZP0930EEP0930EFP0930EGP0930EKP0930EUP0930EVP0930EYP0930FCP0930FDP0930FEP0930FFP0930FGP0930FHP0930FJP0930FKP0930FLP0930FMP0930FNP0930FPP0930FQP0930FRP0930FSP0930FUP0930FVP0930FWP0930FXP0930FYP0930FZP0930HLP0930HMP0930HNP0930HPP0930HQP0930HSP0930HTP0930HVP0930HXP0930HYP0930WGP0931DMP0931DT)