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Snap-on YA-205 welder, Century welder Solar welder wire won't feed

Discussion in 'Troubleshooting and Repair' started by Blenders, Oct 7, 2017.

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  1. Blenders


    Oct 7, 2017

    I have an old wire feed welder I bought when I was in my 20's, (long time ago) and it stopped working. Last spring I found mice had made a nest in it and hence caused a connection to the low voltage transformer to fail. I was able to dig the end of the coil loose, and make new connection and everything was fine. I went to use it for the first time since I repaired and tested it last week, and again no workee. This time the issue is the wire won't feed either by trigger or momentary feed switch. Attached you will find a link that has the schematic, component description, board layout, and some diagnostic procedures. The first thing it says is if there is a wire feed issue, to replace the off board transistor. That has been done, and no change. It is listed in layout off the J5 plug. Pin 3 has 30 volts dc, does not change when momentary is engaged. Pin 2 is 2.7 mv no change during switch engagement. Pin 1 is 2.7 mv drops when switch engaged to near zero.

    I do have good board ground, regulated 23.7 volts on high side. The issue is that under no circumstances can I get and voltage to what is listed as j3, which supplies the power for the feed motor. On a hunch today, I replaced the Q2 transistor because it is the last item to switch the power to that terminal. again no change. This leads me to believe that Q2 is not being triggered properly. I don't know enough about the functions of the parts combined to know where to look next. I do know what diodes do, and resistors etc, but not how they impact each other in a combined fashion. I can include a photo of the actual board if that is needed, but there are no obvious signs of "letting the smoke out", the capacitors are not swollen on the ends, and they seem to charge ok when shorted the connected to dvom, the voltage rises and holds.

    This puts me at a loss as where to go next, I have exhausted my current knowledge. I would be extremely appreciative of any insight you can give me whether it just be "replace part x" or a more detailed assessment of how the system works, and why it is not. ( I love to learn new things, but don't want to waste your valuable time)

    Last thing you need to know for sure is the 2 momentary switches shown in the first pic, are reversed in labeling. The one for the wire feed (inch) is actually the connections on right side of board, and gas purge is actually on left side of board. (both are shown to be the opposite in the diagram.

    Look forward to hearing from you.

    Thanks much!


    Upon further looking, (with my limited knowledge), it seems to me that with the off board transistor, pin 3 should be voltage in which is reading the 30vdc, and when momentary request is pushed it seems to be grounding pin 1. Should that not then produce a voltage output change on pin 2? It is in a socket rather than hard soldered, if pin 2 should get voltage change when pin 1 is grounded, maybe it is defective socket.
    Last edited: Oct 7, 2017
  2. Blenders


    Oct 7, 2017
    Welder has been repaired, 47 cent part. I am not sure, as this is only the second post I have ever made, and neither was responded to if I have done something wrong in posting, or if I have just gone beyond the knowledge or concern of the groups. After numerous attempts at getting some sort of guidance, once again it was personal perseverance and investigation that led to the repair.
  3. duke37


    Jan 9, 2011
    Congratulations on the repair, glad to know it works. What needed to be replaced?

    I imagine that welder repair is not the most common thing to do and without a circuit diagram attached, it needs some enthusiasm to research the circuit.

    I have a welder to sort out here, it has a switch mode supply so uses 340V.:eek:. I will get a round tuit eventually. At the present I am mending an Alba valve radio (only 280V!) and also a picture frame, I need to be awake to use a biscuit jointer.:).
  4. Blenders


    Oct 7, 2017
    Funny thing is, as described (in first paragraph) and at the very top of the post IS a link to the schematic, board layout, parts list, and partial diagnostic procedures.

    In my case it was the variable voltage regulator IC, which I have been told is being used as a current limiter in this case. I am not very versed in electronics, but VERY good common sense, and very good with straight electricity and mechanical things. I just have never really studied semiconductors and how they effect one another. I understand the basic premise of most items individually, but don't have a grasp of the interactions they create.

    Thanks for responding as I now understand it was the way I posted with a link, but I don't know how or another way it should have been done to be more clear.
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