Hey guys, I bought this powermig 180c a ferw years ago and during a little welding project of mine it started to act up. While welding it was as if someone turned the current knob all the way down. I stop and mess with it some and try to weld on the highest amp setting (which I never go up to) and I couldn't weld 1/16" to save my life. Again just like someone turned the adjustment knob all the way down. Just not enough current to melt the metal.
I open it up and do a bunch of testing with the Power Mig 180 Service Manual and according to it I should have line voltage on the output of the pcb. I have line voltage (220v) going in, and when the trigger is pulled it says there should be the same going out. So problem with the board. I took it out and had a look, they actual use a silicone liquid potting on this board. Boy it was hard to remove it. I got most off after what seemed like hours, I find no burnt spots/traces and no components look damaged. I figured maybe the 10k pot went out on the current adjustment knob, also noticed a large triac so I ordered a replacement triac, new 10k pot, new electrolytic caps, and I replaced all the voltage regulators and 3 pin smaller transistor/triacs. Replaced all those componets and crossed my fingers, I hook it all back up but still the exact same! Wire feed works and adjusts fine, fan comes on, solenoid for gas turns on and off, there is just no current to weld with.
So I take a closer look at the board and schematic on page 110 of the manual above and I see a voltage control amp x7 LM224N which feeds an optocoupler IL4208 that controls the main triac src1. I had an LM3224N from another project and replaced it then removed the optocoupler from PCB and it tested fine. When I apply 5vdc to pins 1 & 2 I get different Ω readings so I figured its working. Try board again and it still does the same exact thing. Anyone got any idea where next to look? Am I missing something? Also on the schematic it shows 2 large 55a triacs SCR1 and SCR2 the info on the schematic drawing says the info doesn't apply to all models so I guess that second traic is on another model? Because mine only has the SCR1. The left side of the board is for wire feed and gas valve as well as a spoolgun/spot timer addon kit (which I don't have but want if I ever get this fixed). So the right side is all the current controls. Ive checked all the diodes and resistors (tested with them on the board) and nothing jumps out.
If anyone has a suggestion of something I should test, or to look at, please share. Is there another component on the board that would cause this issue? This issue literately happened while welding, no power outages or lightning strikes, wasn't dropped or got whet. Im out of ideas......This machine was farily new when this happened. I had welded maybe 1 or 2 other projects with it. It was a clean hardley used machine, I just don't get what went out. I can buy a replacement PCB at about $300 but this isnt about saving money or trying to be "cheap", I want to learn more about troubleshooting electronics. If I just went and bought another board for my house gen when it went out, I wouldn't of learned as much as I did when I fiugred out what went out and how to fix it. Ive fixed a family memebers handheld sonogram machine, and other various electronics and I always learn when I do this kind of stuff. If all else fails I guess Ill just buy the replacement board, but id rather spend twice as much time and money and fix this one. lol Im hoping someone sees something or has an idea.
Thanks,
Jeremy
Here are a few pics of the board.
I open it up and do a bunch of testing with the Power Mig 180 Service Manual and according to it I should have line voltage on the output of the pcb. I have line voltage (220v) going in, and when the trigger is pulled it says there should be the same going out. So problem with the board. I took it out and had a look, they actual use a silicone liquid potting on this board. Boy it was hard to remove it. I got most off after what seemed like hours, I find no burnt spots/traces and no components look damaged. I figured maybe the 10k pot went out on the current adjustment knob, also noticed a large triac so I ordered a replacement triac, new 10k pot, new electrolytic caps, and I replaced all the voltage regulators and 3 pin smaller transistor/triacs. Replaced all those componets and crossed my fingers, I hook it all back up but still the exact same! Wire feed works and adjusts fine, fan comes on, solenoid for gas turns on and off, there is just no current to weld with.
So I take a closer look at the board and schematic on page 110 of the manual above and I see a voltage control amp x7 LM224N which feeds an optocoupler IL4208 that controls the main triac src1. I had an LM3224N from another project and replaced it then removed the optocoupler from PCB and it tested fine. When I apply 5vdc to pins 1 & 2 I get different Ω readings so I figured its working. Try board again and it still does the same exact thing. Anyone got any idea where next to look? Am I missing something? Also on the schematic it shows 2 large 55a triacs SCR1 and SCR2 the info on the schematic drawing says the info doesn't apply to all models so I guess that second traic is on another model? Because mine only has the SCR1. The left side of the board is for wire feed and gas valve as well as a spoolgun/spot timer addon kit (which I don't have but want if I ever get this fixed). So the right side is all the current controls. Ive checked all the diodes and resistors (tested with them on the board) and nothing jumps out.
If anyone has a suggestion of something I should test, or to look at, please share. Is there another component on the board that would cause this issue? This issue literately happened while welding, no power outages or lightning strikes, wasn't dropped or got whet. Im out of ideas......This machine was farily new when this happened. I had welded maybe 1 or 2 other projects with it. It was a clean hardley used machine, I just don't get what went out. I can buy a replacement PCB at about $300 but this isnt about saving money or trying to be "cheap", I want to learn more about troubleshooting electronics. If I just went and bought another board for my house gen when it went out, I wouldn't of learned as much as I did when I fiugred out what went out and how to fix it. Ive fixed a family memebers handheld sonogram machine, and other various electronics and I always learn when I do this kind of stuff. If all else fails I guess Ill just buy the replacement board, but id rather spend twice as much time and money and fix this one. lol Im hoping someone sees something or has an idea.
Thanks,
Jeremy
Here are a few pics of the board.