In daily industrial welding operations, the OTC DAIHEN AEP300 and AEP500 welding machines undertake critical welding tasks thanks to their outstanding performance. However, when the equipment encounters unexpected situations, quickly locating and resolving the issue is the key to ensuring production efficiency. If you encounter abnormalities such as failure to strike an arc, an unstable arc, or panel alarms, you can refer to the maintenance and troubleshooting methods provided in this article for a quick diagnosis.
I. AEP300 / AEP500 Basic Troubleshooting Quick Reference
For some of the most basic operational or external connection issues, please first check against the table below for preliminary confirmation:
| Fault Phenomenon | Troubleshooting & Inspection Points |
|---|---|
| No Arc Ignition | Is the power switch turned off? |
| Is there a phase loss? | |
| Is the fuse of the input side switch blown? | |
| Is the torch switch correctly connected, or is the wire broken? Is the workpiece cable correctly connected? | |
| Unstable Arc | Are the cable connections loose? |
| Is the shielding gas flow appropriate? | |
| In AC TIG welding, is the selected cleaning width appropriate? Is the tip of the tungsten electrode rough or whitened? | |
| Cannot Set Current | Is the current setting toggle switch correctly selected? |
| When using a remote control pendant, check if it is properly connected. | |
| Cannot Shut Off Shielding Gas | Is the gas check switch S4 set to the “Check” position? |
| No Shielding Gas Output | Is the gas supply hose correctly connected? |
| Is the gas volume appropriate? | |
| Is the gas cylinder valve open? | |
| Is the machine mistakenly set to MMA (Stick) welding mode? | |
| Cannot Extinguish Arc | Is the crater fill setting switched to “ON” or “Repeat”? |
| No High Frequency (HF) Generated | Is the torch switch correctly connected, or is the wire broken? |
| Is the machine mistakenly set to MMA (Stick) welding mode? | |
| Is the workpiece cable for MMA welding improperly connected? |
II. AEP300 / AEP500 In-Depth Fault & Resolution Chart
If the preliminary checks fail to resolve the issue, or if the equipment indicators light up abnormally, please refer to the detailed fault list below for in-depth troubleshooting of the power source interior or circuit boards:
| No. | Fault Phenomenon | Cause of Fault / Abnormality | Troubleshooting Method | |
|---|---|---|---|---|
| 1 | Main Power Indicator PL1 is OFF | Power switch ON, fan runs | Indicator PL1 bulb fault | Check/replace indicator PL1 |
| Power switch ON, fan does not run | Distribution box switch not turned on | Check distribution box | ||
| Fuse F1 blown | Check and replace fuse F1 | |||
| 2 | Power Switch ON, Fan Does Not Run | Main power indicator PL1 is OFF | Refer to No. 1 troubleshooting | |
| Main power indicator PL1 is ON | Fuse F1 blown | Replace after finding the cause (T2, FM) | ||
| Fan fault | Check or replace fan | |||
| 3 | Abnormal Indicator PL2 is ON After Power ON | Poor connection of CN1 on PCB2 | Insert CN1 connector firmly in place | |
| Insufficient water pressure | Refer to No. 9 troubleshooting | |||
| Pressure switch PS fault | Refer to No. 9 troubleshooting | |||
| Torch switch is in “ON” state when power is turned on | Turn off the torch switch once and then turn it on | |||
| 4 | Abnormal Indicator PL3 is ON After Power ON | Thermostat TH1 or TH2 fault | Replace TH1 or TH2 | |
| Fan does not run | Replace fan | |||
| Exceeds rated duty cycle | Use within the rated duty cycle range | |||
| 5 | No Shielding Gas Flows After Pressing Torch Switch | No gas flows even if gas check switch S4 is set to “Check” | Cylinder outlet valve is closed | Open the outlet valve |
| Insufficient gas pressure in cylinder | Check gas pressure | |||
| +24V power circuit fault (PL1 on PCB1 is OFF) | Replace PCB1 circuit board | |||
| Solenoid valve SOL fault | Check solenoid valve SOL | |||
| Gas flows after setting gas check switch S4 to “Check” | Gas control circuit fault | Replace PCB2 circuit board | ||
| Control cable (2-core) broken or socket poor contact | Check wires 81, 82; replace control cable | |||
| Filter circuit fault | Replace PCB3 circuit board | |||
| Abnormal indicator PL2 is ON | Refer to No. 3 troubleshooting | |||
| 6 | Cannot Shut Off Shielding Gas | Gas check switch S4 set to “Check” | Switch S4 to “Weld” mode | |
| Gas control circuit fault | Replace PCB2 circuit board | |||
| Solenoid valve SOL fault | Check solenoid valve SOL | |||
| 7 | No High-Frequency (HF) Spark Generated Upon Switch Press | Spark discharge sound is heard inside the power source | No shielding gas flows | Refer to No. 5 troubleshooting |
| Fuse F2 blown | Check and replace fuse F2 | |||
| AC contactor MS fault | Replace AC contactor MS | |||
| HF transformer T3 fault | Replace HF transformer T3 | |||
| Wire-wound resistor R6 broken | Replace wire-wound resistor R6 | |||
| HF generation circuit fault | Replace related PCB or grind electrode; disconnect MMA electrode holder | |||
| No spark discharge sound inside the power source | Tungsten electrode whitened/oxidized | Grind the tungsten electrode | ||
| MMA electrode holder connected to “-” terminal (HF Leakage) | Correct the connection setup | |||
| 8 | HF Generated But Fails to Strike an Arc | Arc appears after touching electrode to workpiece | Tungsten electrode whitened | Grind the tungsten electrode |
| Electrode too thick or current set too low | Select correct electrode size, set correct current | |||
| Switch to MMA mode, multimeter shows no open-circuit voltage | Thyristor (SCR) 1, 2 fault | Replace thyristors SCR1, 2 | ||
| Arc ignition pulse circuit fault | Replace PCB5 circuit board | |||
| Control circuit fault | Replace PCB1 circuit board | |||
| 9 | In TIG welding with “Water-Cooled Torch”, no action upon switch press | Abnormal indicator PL2 is ON | Insufficient water pressure or pressure switch fault | Increase water pressure, replace pressure switch |
| Supply and return water connections reversed | Correct the hose connections | |||
| Abnormal indicator PL2 is OFF | Control cable (2-core) broken or torch switch fault | Replace control cable or torch switch | ||
| Control circuit fault | Replace PCB2 circuit board | |||
| Power circuit fault | Replace PCB1 circuit board | |||
| (Indicator PL1 on PCB1 is OFF) | ||||
| 10 | Welding Base Current & Pulse Current Settings Invalid | Initial current, crater fill current settings also invalid (cannot set) | Sequence circuit fault | Replace PCB2 circuit board |
| Control circuit fault | Replace PCB1 circuit board | |||
| Arc ignition pulse circuit fault | Replace PCB5 circuit board | |||
| Initial current, crater fill current settings normal | Remote pendant and jumper switch “SW2” settings inconsistent | Set jumper switch “SW2” correctly per application | ||
| Remote control cable broken or poor contact | Check/replace remote control cable | |||
| Filter circuit fault when using remote | Replace PCB3 circuit board | |||
| Current setting potentiometer fault | Replace potentiometer | |||
| 11 | No Pulse Even if Pulse Switch is Set to “ON” | Sequence circuit fault | Replace PCB2 circuit board | |
| 12 | Initial Current Setting Invalid (Cannot Set) | Crater fill current setting normal | Sequence circuit fault | Replace PCB2 circuit board |
| Initial current potentiometer R18 fault | Replace potentiometer R18 | |||
| Crater fill current setting also invalid | Sequence circuit fault | Replace PCB2 circuit board | ||
| Control circuit fault | Replace PCB1 circuit board | |||
| 13 | Crater Fill Current Setting Invalid | Sequence circuit fault | Replace PCB2 circuit board | |
| Control circuit fault | Replace PCB1 circuit board | |||
| Arc ignition pulse circuit fault | Replace PCB5 circuit board | |||
| Crater fill potentiometer R17 fault | Replace potentiometer R17 | |||
| 14 | Down-Slope Time Unadjustable During Crater Fill “ON”, “Repeat”, or Spot Welding | Sequence circuit fault | Replace PCB2 circuit board | |
| Down-slope potentiometer R14 fault | Replace potentiometer R14 | |||
| 15 | Arc Self-Hold Fails During Crater Fill “ON”, “Repeat”, or Spot Welding | Sequence circuit fault | Replace PCB2 circuit board | |
| Control circuit fault | Replace PCB1 circuit board | |||
| Internal fault in Hall sensor CT1 | Replace CT1 | |||
| 16 | Cannot Adjust Cleaning Width | Control circuit fault | Replace PCB1 circuit board | |
| Cleaning width potentiometer R23 fault | Replace potentiometer R23 | |||
| 17 | Arc Spot Welding Time Unadjustable | Arc spot welding time circuit fault | Replace PCB2 circuit board | |
| Spot welding time potentiometer R14 fault | Replace potentiometer R14 | |||
| 18 | Hard to Strike Arc at Low Current in DC TIG Welding | Fuse F3 blown in start compensation circuit | Check and replace F3 | |
| Control circuit fault | Replace PCB1 circuit board | |||
| Diode DR1 or DR3 fault | Replace diode DR1 or DR3 | |||
| Resistor R1 or R2 fault | Replace resistor R1 or R2 | |||
| 19 | Irregular High Current Surge Upon Arc Ignition | WCR detection circuit fault | Replace PCB2 circuit board | |
| Anti-surge irregular high current circuit fault | Replace PCB1 circuit board | |||
| 20 | Large Current Uncontrollable | Thyristor SCR1, 2 fault | Replace thyristors SCR1, 2 | |
| Thyristor drive circuit fault | Replace PCB5 circuit board | |||
| Control circuit fault | Replace PCB1 circuit board | |||
| Hall sensor CT1 fault | Replace Hall sensor CT1 | |||
| Current feedback circuit fault | Replace PCB2 circuit board | |||