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Thread: Newly acquired Powcon 300 SM cannot hold stick arc

  1. #1
    Join Date
    Dec 2007
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    Bay Area, CA
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    Newly acquired Powcon 300 SM cannot hold stick arc

    Hi. I just bought a Powcon 300 SM off Craigslist. The power cord was cut off so I could not try it before I bought it. The seller said that it was removed from being hardwired to 3 phase at his company, and it was working when it was removed. I brought it home and connected it to single phase 240 V with a big resistor to make sure that the input capacitors were properly formed. The fan and display powered up just fine, and a minimal current was flowing through the resistor. The output voltage was about 60 V DC, measured on an analog meter. The machine was making a ticking sound. According to posts I have seen, this means that the welder should be working.

    There was one problem. The stick/MIG switch was broken and pushed into the case. I didn't notice this when I picked up the welder. I contacted the seller, and he said that the machine was only used in stick mode, so the setting should be in the right place. When I tried to start an arc with about 60% on the low amperage setting with 7018 electrode positive, there was an arc, but it was impossible to hold it steady. My Miller Thunderbolt is much better. The rod easily stuck and became red. I tried 6013, and it was a little better, but not usable. I suspect that the stick/MIG setting switch is the problem, but I cannot easily determine the current setting. The wiring to the switch looks very strange. One pole (the lower one) has both yellow wires shorted together so the connection is the same no matter what position the toggle is in. I looked around for a manual or wiring diagram, but could not find one on the web. There are a lot of pointers, but they lead to dead ends. Does anybody have some information about this switch and how the wires are supposed to be connected to it. I could just put another switch in if I knew. Thanks!

  2. #2
    Join Date
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    Re: Newly acquired Powcon 300 SM cannot hold stick arc

    https://diagramas.diagramasde.com/otros/300SM.pdf
    Try this link for a manual.
    The switch is a 3 position on,off,on switch. should have 4 wires going to it and
    the middle connection is jumpered. 6 connection to the switch so it is two switches in one housing called a double pole , double throw center off.
    one side should have two wires and the centered jumped to center.
    the other side has one wire and it is jumpered to the outside contacts.
    In the center off position you are in short arc mig. no wires are connected.
    spray mig and stick are the on settings. diagram only gives one color. brown is jumpered to the center connections.
    Should be able and get a switch from any electronic supply house and some electric supply houses. or appliance parts store.

  3. #3
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    Dec 2007
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    Re: Newly acquired Powcon 300 SM cannot hold stick arc

    Hi ccawgc. This URL has the manual! Thank you very much. I pulled off the front panel and removed the broken switch. After desoldering it and replacing it with a good switch, an out of circuit test revealed that it was stuck in the short arc MIG setting, unlike what the seller told me. He has broken contact with me anyway, probably due to too much pestering. The new switch works great, and the welder welds great. It makes an interesting noise. Nothing much to add, except a heartfelt thanks for your clear post and directions.

  4. #4
    Join Date
    May 2007
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    Re: Newly acquired Powcon 300 SM cannot hold stick arc

    Quote Originally Posted by evfreek View Post
    eat. It makes an interesting noise. ns.
    lol, does it whistle at you, or does it make a "tic, tic " noise, like an old fashioned clock

  5. #5
    Join Date
    Dec 2007
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    Re: Newly acquired Powcon 300 SM cannot hold stick arc

    Yes. It does make the ticking sound. Then, there are winding up noises depending on the current flow. It sounds strange, but all my welders sound different, and it is definitely quieter than my buzz box.

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