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  1. #1
    Join Date
    Apr 2020
    Location
    Australia
    Posts
    5

    Default Ozito MWR - 135 -- Welding current but no motor or feed

    I picked this welder off the side of the street a couple years ago and have only just gotten round to having a look at it.
    So far I've:
    • Fixed the CR1 relay and checked to make sure CR2 is functional.
    • Tested the feed motor with a 12v battery and confirmed that it does indeed feed


    The high current welding circuit is working fine, but the motor does absolutely nothing. I measured the voltage coming into the feed regulation from pins 2 and 5 but I only get 3V when the welder is set to a voltage other than 0v. on 0, I only measure areound 2.5V.

    Any ideas?
    bt-gw190d_1e5c937.jpg

  2. #2
    Join Date
    Sep 2005
    Location
    Bendigo
    Age
    60
    Posts
    419

    Default

    From the way I read that circuit pins 2 and 5 are the external DC supply to that circuit, therefore your external power supply is faulty.

  3. #3
    Join Date
    Apr 2020
    Location
    Australia
    Posts
    5

    Default

    Right. I'll have a look tomorrow and see if I can find anything suspicious.

  4. #4
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    Look for simple things first.
    If the gun cable is a permanent connection , try the trigger switch mechanism. Check the mechanical on off function and then the electrical function.

    Can't speak for machines these days but years back the trigger, or trigger cable connections were a common source of failure.

    A real rrsole trick was to wrap one of the connector pins (on an industrial unit) in sticky tape, when someone went for smoko.

    When they came back Voila! the mig wouldn't work

    Grahame

  5. #5
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
    Age
    71
    Posts
    5,945

    Default

    Grahame, that's nearly as bad as black cardboard in the welding mask. This was prior to the auto darkening helmets.
    To grow old is mandatory, growing up is optional.

  6. #6
    Join Date
    Apr 2020
    Location
    Australia
    Posts
    5

    Default

    Well, I checked the voltage on the board input again and i now measure 30v. So that seems to be working now. I also checked the voltage across the CR2 relay and found that there was only around 4.2v even though the transformer seems to be outputting 7v when under load. CR1 seems to work fine but CR2 just won't trigger. I used a 12v battery to activate the coil on CR2 and found that the feeding worked. I did have to rewind CR1 with a slightly thicker wire to get it to work. Maybe the coil is drawing more power than it originally did?

  7. #7
    Join Date
    Apr 2020
    Location
    Australia
    Posts
    5

    Default

    Ok, I did some calculations and I'm pretty sure this is the problem. The rewound relay only has 7.2 ohms of resistance where as the CR2 relay has 400 ohms.

  8. #8
    Join Date
    Apr 2020
    Location
    Australia
    Posts
    5

    Default

    After doing some more testing I belive this is the issue. I'm just going to buy a suitable replacement on ebay and hope it works. Thanks for all the help, guys!

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