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Thread: Did these old machines just work like this?

  1. #1
    Join Date
    Sep 2021
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    Did these old machines just work like this?

    I have an old Hobart TG-201 (circa 1970) that has an unknown history and was given to me. I got it working today - preflow, postflow, AC/DC, water chiller, HF, foot pedal - everything. It has a couple of quirks, though. The fine power regulation didn't work at first and I had to replace some leads on the saturable core transformer. Now that everything is working, the 35A-290A setting only seems to be putting out about 100A or so. And the other two settings seem to drop off another 1/3rd each from there. And the fine regulation only seems to be able to pull it down to 75A or so. Maybe not even that. I checked inside the machine and the fine adjustment and the foot pedal are feeding variable voltages to the saturable core, but it doesn't seem to be enough to make a big difference.

    Were these old machines like that, or do I have more work to do?

  2. #2
    Join Date
    Mar 2010
    Location
    Ceres, California
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    Re: Did these old machines just work like this?

    Most of these old units did not have a large swing in current control. that is why they also had range taps. How it works depends on if it is a mag amp or a saturable reactor. If it is a saturable reactor and you remove the control current (signal).
    The welder output will drop to the minimum of each range. AS you raise the control current the welder output should rise proportionally to the max output of the range.
    Provided the line voltage is set up correctly. The mag amp just works the other way. you add control current to lower the welder output. Some require the control voltage to go from a positive value to an equal negative value. Both of these are series AC devices. Bad or shorted weld diodes will affect the welder output.
    You can call the Hobart welder tech support and ask for the manual to be emailed to you for free. printed copy cost. Go to their web site for their phone number.
    If you get lucky there might be one of the old timers around who know something about the welder. have the serial number and spec numbers with you when you call.

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