Snap On FM140A tripping breaker upon hitting mig trigger
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  1. #1

    Snap On FM140A tripping breaker upon hitting mig trigger

    I picked this welder up off craigslist today. I probably paid too much considering the issue it has.

    It turns on fine, but one you hit the trigger it will dim all the lights on a 20amp gfci, and after about 3 seconds trip it or the main. This is no welding mind you and just hitting the trigger without striking an arc.

    It will strike an arc for a brief second before it pops the breaker.

    I noticed quite a bit of arcing coming from the distribution block, or switch, whatever it is.

    Any ideas where to look,? I paid 200 for the welder. I'm hoping to make a nice little welder out of it, but I dont want to drop a arm and a leg into it.

  2. #2
    Join Date
    Dec 2012
    Location
    North Texas
    Posts
    187

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    I'd start where it is arcing internally and work out from there myself . . .

    - Tim

  3. #3
    Join Date
    May 2009
    Location
    Wyoming US
    Posts
    2,233

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    On average, the problem would be shorted output diodes.
    Hobart T225
    HF 151/2 Cap mod
    HF 131/2 Cap mod
    Miller Cricket XL
    Century Portable Mig
    O/A

  4. #4

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    Thanks for the suggestion on the diodes.

    I took them off and did a ohm test with my multimeter. JUst a regular test, and I am seeing continuity both ways on both diodes. I assume both are bad. I dont have a diode mode on my multimeter, but I am assuming just checking continuity both ways will give me an accurate read?


    Anyhow, I found some suggested replacements at newark. LOoks like they have 2 of the the bottom diode in stock. I'm pretty sure this will work as a replacement for the 1n3290?

    http://www.newark.com/jsp/search/bro...questid=182597

  5. #5
    Join Date
    May 2009
    Location
    Wyoming US
    Posts
    2,233

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    Looks like plenty of volts and amps,if the polarity is right.
    Is it a 2 diode type rectifier ?
    Hobart T225
    HF 151/2 Cap mod
    HF 131/2 Cap mod
    Miller Cricket XL
    Century Portable Mig
    O/A

  6. #6

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    i'm not too familiar with electronics, but it only uses 2 of the same diodes mounted on the aluminum plate, with a heavy duty bar coming off each.

  7. #7
    Join Date
    Dec 2012
    Location
    North Texas
    Posts
    187

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    Quote Originally Posted by airbats801 View Post
    Thanks for the suggestion on the diodes.

    I took them off and did a ohm test with my multimeter. JUst a regular test, and I am seeing continuity both ways on both diodes. I assume both are bad. I dont have a diode mode on my multimeter, but I am assuming just checking continuity both ways will give me an accurate read?


    Anyhow, I found some suggested replacements at newark. LOoks like they have 2 of the the bottom diode in stock. I'm pretty sure this will work as a replacement for the 1n3290?

    http://www.newark.com/jsp/search/bro...questid=182597
    Yup . . . diode mode only runs a higher test voltage since higher end meters are so low a test voltage that they can't overcome the .7v drop of a silicon diode. You don't say what resistance you read, but the same (and low) both ways is a dead diode on any meter.

    - Tim

  8. #8

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    i forget what range i was on, but it was around. 003 both ways

  9. #9

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    Well, I just wanted to wrap this up so anyone who searches in the future can find a valid part number. I hear the diodes from snap on are around $75 a piece

    I ordered 2 at 29.95ea from Newark online

    Newark Number 15M1927
    Suggested replacement for: 1n3290
    Mfg. Number NTE6155


    Installed them, no mods needed, and she no longer trips the breaker Thanks for all the help, and hopefully this can help any snap on fm140 users in the future that encounter the same problem I had.

  10. #10
    Join Date
    Jan 2013
    Location
    Everett, WA
    Posts
    106

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    Thanks for the follow up! Someday you will be what google pulls up when someone else has the same issue, and instead of another dead-ended and long forgotten thread, they will get an answer.

  11. #11

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    A bit of a update, sorry not sooner. I no longer trip the breaker, but I get a puff of smoke from some other electronics while striking an arc. We decided to stop trying to weld when seeing it puff after a few seconds. I have no freaken idea at this point. Maybe tomorrow I will post a picture and someone can help me out again. It would be nice to actually use this welder, I need to start fabbing some exhaust soon, and I still havent got this thing sorted.

    actually, here is a picture. It's the blue whatevers in the picture. They seem to expand and puff after a few seconds,

  12. #12

    Re: Snap On FM140A tripping breaker upon hitting mig trigger

    After reading up on smoking caps. I have a feeling they just degraded from sitting for so many years. The service manual just lists the 4 capacitors as 1000th 50v. Are there any other specifications I should look for when buying these?

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