What am I looking at?

[chrismunn]

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[/URL][/IMG] I'll preface this by saying that I'm not an electronics guys and know just enough to make things worse but.... I'm trying to test these MOSFETs and this relay on a cicuit board out of a cheap mig welder to see if they're bad. I've watched a few videos to see how to test the MOSFET but I'm not sure how to interoperate the readings I'm getting. I'm not even sure exactly what setting I have my multimeter on but I'll post a pic of the function I'm testing on. Also, the components are still attached to the board. I'm not sure if that matters? I'm testing both mosfet the same way with negative lead on the source pin and positive to the gate and drain pins seperatly.

One of the mosfet is a IRF640N. On this I get a multimeter reading of .338v between source and drain and a reading of .728v between source and gate.

On the other mosfet IRF510 I get .506v between source and drain and 0 between source and gate.

Also, how can I test that relay?

[/URL][/IMG] The problem I'm trying to fix is a mig welder with a feed motor that no longer feeds. The motor is good, I've taken it out of the machine and powered it up and it runs fine. All the other functions of the machine operate fine. I'm just not getting power to that motor and it's somewhere at the board. I've tested all the connections afyer the board and they're all fine. A general look at the board, everything looks fine. Nothing appears to be melted or burnt except a couple pins on the IRF640N mosfet that look like they could have been pretty warm at some point?

What do you guys think?

 

[chrismunn]

Not sure why my photos didn't post? Does this forum work with photobucket?

 

[chrismunn]

 

[chrismunn]

 

[chrismunn]

 

[chrismunn]

 

[chrismunn]

Wrong forum?

 

[hevans1944]

Wrong forum?

Perhaps. Electronics Point might even be the wrong website.

Have you tried to find a user group forum for your welder? The cheaper the product, the more it needs a good user group to diagnose and solve problems the manufacturer may choose to ignore. After all, youse paid yer moneys and youse got their products... now go away and let us sell this junk to someone else. There be no profit made in working with you after the sale.

You haven't provided any information that might be useful for troubleshooting your feed problem, other than your opinion that the feed motor is okay. Making "measurements" with your digital multimeter without understanding what you are measuring or why you are measuring it is not troubleshooting. You haven't provided any schematics of the circuitry involved, which would allow us to make suggestions about how to troubleshoot your problem.

And, it is generally NOT a good idea to try to determine the functionality (or lack thereof) of a component that is soldered in place with other components. Carefully remove the component (so as not to damage it) and test it according to the specifications found on its datasheet. You did download the datasheets for the two mosfet components, riiiight?