（1）電源模塊故障。一個工作正常的電源模塊，其上面的工作指示燈如“AC”、“24VDC”、“5VDC”、“BATT”等應(yīng)該是綠色長亮的，哪一個燈的顏色發(fā)生了變化或閃爍或熄滅就表示那一部分的電源有問題。“AC”燈表示PLC的交流總電源，“AC”燈不亮?xí)r多半無工作電源，整個PLC停止。這時就應(yīng)該檢查電源保險絲是否熔斷，更換熔絲是應(yīng)用同規(guī)格同型號的保險絲，無同型號的進(jìn)口熔絲時要用電流相同的快速熔絲代替。如重復(fù)燒保險絲說明電路板短路或損壞，更換整個電源。“5VDC”、“24VDC”燈熄滅表示無相應(yīng)的直流電源輸出，當(dāng)電源偏差超出正常值5%時指示燈閃爍，此時雖然PLC仍能工作，但應(yīng)引起重視，必要時停機檢修。“BATT”變色燈是后備電源指示燈，綠色正常，黃色電量低，紅色故障。黃燈亮?xí)r就應(yīng)該更換后備電池，手冊規(guī)定兩到三年更換鋰電池一次，當(dāng)紅燈亮?xí)r表示后備電源系統(tǒng)故障，也需要更換整個模塊。 （2）I/O模塊故障?！　≥斎肽K一般由光電耦合電路組成；輸出模塊根據(jù)型號不同有繼電輸出、晶體管輸出、光電輸出等。每一點輸入輸出都有相應(yīng)的發(fā)光二極管指示。有輸入信號但該點不亮或確定有輸出但輸出燈不亮?xí)r就應(yīng)該懷疑I/O模塊有故障。輸入和輸出模塊有6到24個點，如果只是因為一個點的損壞就更換整個模塊在經(jīng)濟上不合算。通常的做法是找備用點替代，然后在程序中更改相應(yīng)的地址。但要注意，程序較大是查找具體地址有困難。特別強調(diào)的是，無論是更換輸入模塊還是更換輸出模塊，都要在PLC斷電的情況下進(jìn)行，S5帶電插拔模塊是絕對不允許的?！。?）CPU模塊故障?！　⊥ㄓ眯蚐5 PLC的CPU模塊上往往包括有通信接口、EPROM插槽、運行開關(guān)等，故障的隱蔽性更大，因為更換CPU模塊的費用很大，所以對它的故障分析、判斷要尤為仔細(xì)。表1-1例出了CPU模塊常見故障及處理方法。檢修實例：一臺PLC合上電源時無法將開關(guān)撥到RUN狀態(tài)，錯誤指示燈先閃爍后常亮，斷電復(fù)位后故障依舊，更換CPU模塊后運行正常。在進(jìn)行芯片級維修時更換了CPU但故障燈仍然不停閃爍，至到更換了通信借口板后功能才恢復(fù)正常。

FALK RAM GEAR DRIVE MODEL 21HMHQ2A166, 5HP, 16.64 RATIO

SAFTRONICS EZ6-125 SOLID STATE REDUCED VOLTAGE MOTOR ST

THERMO ELECTRON PX2 THERMAL CYCLER & HYBAID HBPXBG02 96

BECKMAN PTS-2000 CENTRIFUGE 4 PLACE SWINGING BUCKET ROT

INFORS HT AQUATRON WATER BATH SHAKER 20-400 RPM AMBIENT

HARRICK SCIENTIFIC SPECTROCOSCOPY REFLECTION ACCESSORY

HARRICK SCIENTIFIC SPECTROCOSCOPY REFLECTION ACCESSORY

PUFFER HUBBARD IGL2023A18 LABORATORY FREEZER

UGO BASILE 7371 PLANTAR TEST W/7372 IR EMITTER

NUAIRE NU-430-400 SERIES 7 CLASS 2 TYPE B BIOLOGICAL SA

COHERENT INNOVA 1300C-FRED LASER POWER SUPPLY

SIEMENS 599 SERIES 6" VALVE & 12" PNEUMATIC ACTUATOR

SHIMADZU FCV-14AH, FCV-11AL & SUBCONTROLLER VP

R&D DRUM MOUNTS PARTS CLEANER ?IN BOX

ADEPT TECHNOLOGIES MCP-4 10332-11506 ROBOTIC CONTROL PE

C.B.S. SCIENTIFIC CO. DGGE-4000 DENATURING GRADIENT GEL

BECKMAN TYPE 45TI 45,000 RPM CENTRIFUGE ROTOR

HEAT SYSTEMS-ULTRASO?NICS, INC. W-225R SONICATOR CELL DI

FIKE CV-CF BI 24"X 30" EXPLOSION VENT

JVC GY-DV300 3-CCD PROFFESIONAL DV CAMCORDER & TEAC DWE

SHIMADZU LC-10AD LIQUID CHROMATOGRAPH PUMP

VARIAN DS302 / LEROY SOMER VACUUM PUMP

HAAKE D1 DIGITAL WATER BATH TYP 0004493

VIBATORY FEEDER 35"DIA X 54"H

WILKERSON WRD50A-1RS REFRIGERATED AIR DRYER

WORCESTER ELECTRO-PNEUMAT?IC ?CPT THROTTLE CONTROL VALVE

SCIEX 019295/014368 MASS SPECTROMETER HEATED NEBULIZER

DRESSER CONSOLIDATED VALVE, TYPE 1905QC-2-34, SIZE 6 X

LAB LINE 3527 ORBIT ENVIRON SHAKER

COHERENT INNOVA I90C-4-FRED LASER POWER SUPPLY

EG&G ROTRON / BALDOR 30HP MODEL DR14DW86W MOTOR

DUPONT SORVALL GS-3 3000 RPM 6 POSITION FIXED ANGLE CEN

FISHER SCIENTIFIC ISOTEMP PLUS REFRIGERATOR 13-986-120

PARKER 323-9539-220 HYDRAULIC PUMP GEAR, FIXED DISPLAC

TEKNOGARD REFRIGERATOR MODEL TEK-23SF 27" x 29-1/2" x 8

BIOROBOTICS BP-800 201-0763 AUTOMATED SYSTEM ACCESSORY

WINDSOR VOYAGER 2 CARPET EXTRACTOR

COPYPRO POWERPRO CD DVD THERMAL LABEL PRINTER

CONSOLIDATED BEARING CO. HMS-3084 LOCKNUTS COMPLETE WIT

NUAIRE MODEL NU-430-600 SERIES 29 BIOLOGICAL SAFETY CAB

NUAIRE MODEL NU-430-600 SERIES 23 BIOLOGICAL SAFETY CAB

SEW-EURODRIVE GEAR REDUCER, TYPE: KL06, RATIO 130.16:1

NUAIRE MODEL NU-603-630 SERIES 3 REVERSE FLOW LAMINAR F

SORVALL SA600 ROTOR AUTOCLAVABLE 121'C 17500RPM MAXIMUM

BN-3133 CAROUSEL MULTIPLE SYNTHESIS 12 REACTION STATION

BURLEIGH GIBRALTAR 8" X 8" X-Y STAGE PLATFORM MOUNT APP

WELCH-THOMAS 2585B-50 DRY VACUUM PUMP

SQUARE-D M800S 800A SURFACE MOUNT TYPE 1 CIRCUIT BREAKE

BECKMAN COULTER #343890 FRACTION RECOVERY SYSTEM PUNCTU

SERVOLIFT EASTERN 502-4R-CW REFRIGERATED SERVER

SERVOLIFT EASTERN 500-2 STATION WITH WELLS CHAR BROILE

SquareD PKA36200GN I-LINE CIRCUIT BREAKER 4SERIES 3P4W

Square D PKA36150GN I-LINE CIRCUIT BREAKER 4SERIES 3P4W

YARWAY SOCKET WELD VALVE 1 1/2" P/N 6981

Square D PKA36125GN I-LINE CIRCUIT BREAKER 4SERIES 3P4W