SA-250 wiring
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Thread: SA-250 wiring

  1. #1
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    SA-250 wiring

    I'm working on a SA-250 serial # A-1120172 code 9327-P
    It had not been run in several years and I now have it running, welding, and generating AC but...
    By accident the work clamp touched the welder frame and sparks flew.
    I then started testing voltage and resistance.
    From the welding studs to the frame:
    Positive stud: 49 volts DC and 105 volts AC (scary); dead short for resistance
    Negative stud: 49 volts DC and 0 volts AC; dead short for resistance
    Between welding studs:
    94 volts DC
    218 volts AC (even scarier)
    Have looked as best I can and don't see any frayed wires or wires touching the housing.
    While the machine is running there is no obvious arcing or smoking.
    Looking at the wiring diagram I wondered if the full wave bridge rectifier might be part of the problem but wanted the forum's advice before I went any farther.
    Any suggestions for repair?
    As a side note I have removed the battery so no one starts it.

  2. #2
    Join Date
    Dec 2010
    Location
    Pacific Northwest
    Posts
    818

    Re: SA-250 wiring

    Go here-

    http://www.lincolnelectric.com/asset...OLN3/IM288.pdf

    Scroll down to page 16 - View the "OLD STYLE OUTPUT PLUG"

    There is an insulator around the studs. If this insulator breaks down, the lead connector will short to the machine frame. Unknown to the welder, he touches either the hot lead or the ground to the machine frame and gets some sparks.

    This is the first point I always check since it is very easy to inspect.

    Look for the easy problem first.

    Good Luck,

    Hobo
    Lincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.

  3. #3
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    Re: SA-250 wiring

    Thanks Hobo,
    Easy is always good but I'm afraid not the problem in this case.
    Insulators tested good.
    Really confused about AC on the DC side.
    Kirby

  4. #4
    Join Date
    Dec 2010
    Location
    southeast texas
    Posts
    327

    Re: SA-250 wiring

    The rectifer may be out but theres also a transformer that may be shorted out leaking voltage to weldee frame
    1960 Redface SA-200 F 162
    1973 Black face SA-200 F 163 with 5" chop
    2013 Miller Trailblazer 275
    2013 GMC 3500 welding car

  5. #5
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    Re: SA-250 wiring

    Redfacer,
    I isolated the current transformer, no change.
    Thanks for the suggestion.

    Checked resistance from the commutator (at the main brushes) to the frame at 2/10 ohm.
    Then pulled the brushes off the commutator and checked welding studs to frame; open circuit on both
    With brushes pulled back, resistance from commutator to armature shaft end is 2/10 ohm.
    I afraid this means a shorted armature.
    Correct or am I missing something?
    Thanks for all the help

  6. #6
    Join Date
    May 2012
    Location
    Cleveland Tx
    Posts
    54

    Re: SA-250 wiring

    The two most common problems with those machines is the flashing diode and the rectifier. If those check out good then move on to the A/C exciter frame, to check that you measure the OHMs between the yellow to yellow wires, remove the yellow wires from the fuse block and measure across them both, your reading should be.5 OHM. + or - 10%. if that checks out good then remove the brushes and OHM across the slip rings it should measure 41 OHMs. And that should tell you what you need to know, any questions, feel free to contact me.
    1950 SA-200 Shorthood
    1961 SA-200 Red Face X2

  7. #7
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    Re: SA-250 wiring

    Thanks circlec,
    I've checked flashing diode and bridge rectifier. Both OK.
    Yellow to yellow is .4 ohm and across slip rings 41 ohms with brushes up

    So resistance main commutator bars to shaft end doesn't indicate anything?

    I followed the trouble-shooting diagram from the Weldmart site for the 250.
    Only thing off was the voltage at the ac connector (yellow) where there is supposed to be 125 vdc.
    I only had 16 volts but my testing is suspect given running machine and voltages near my hands....

    Should there be continuity between the neutral at the 120 receptacle and the frame?
    Mine is open circuit.

  8. #8
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    Re: SA-250 wiring

    I've talked to Bill and Kaye at Bill's Welder Repair. (really helpful and nice people)
    Bill confirmed my fear that the main armature is shorted.
    Key was resistance from commutator to frame.
    Any suggestions for where to purchase an armature?

  9. #9
    Join Date
    Jun 2011
    Location
    northwestern New Jersey
    Posts
    490

    Re: SA-250 wiring

    Motor rewind shops do this type of work all day long. Look in yellow pages for motor shops. Just my thoughts. Best Bob

  10. #10
    Join Date
    Dec 2010
    Location
    southeast texas
    Posts
    327

    Re: SA-250 wiring

    Tom Fowler (Phone: 985.384.6914) sells them all day long for 1200, you send yours and he sends you a freshly rebuilt one
    1960 Redface SA-200 F 162
    1973 Black face SA-200 F 163 with 5" chop
    2013 Miller Trailblazer 275
    2013 GMC 3500 welding car

  11. #11
    Join Date
    May 2012
    Location
    Cleveland Tx
    Posts
    54

    Re: SA-250 wiring

    Measure the OHMs from the commutator bar to the end of the shaft. red to the bar black to a clean spot on the shaft. read in MEG OHMs, anything better than 1 is good according to Lincoln. I like 2.
    1950 SA-200 Shorthood
    1961 SA-200 Red Face X2

  12. #12
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    Re: SA-250 wiring

    Need advise,
    I've got the 250 pulled apart for the armature repair.
    While it's down should I replace the shunt coils?
    Based on what I've read this one has aluminum coils that may cause problems.
    Octagonal barrel, 1988 production date, and code 9327.
    The current coils read 45 ohms and it was welding fine.
    I do plan on keeping this machine for personal use on the farm and pickup jobs.
    It won't get heavy use but it needs to be reliable.
    Thanks for all your help

  13. #13
    Join Date
    Dec 2010
    Location
    Pacific Northwest
    Posts
    818

    Re: SA-250 wiring

    I just put up a few photos of aluminum coils in the generator. You might want to look at them if you suspect you have aluminum.

    http://weldingweb.com/album.php?albumid=1381
    Lincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.

  14. #14
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    Re: SA-250 wiring

    Thanks Hobo
    I have looked closely at my coils and connections and don't see any oxidation like that in your pictures.
    There is a spot on one of the shunt coils where the red coating had peeled back.
    The winding there are bright copper.
    I have attached pictures for you to comment on.
    Note that this machine came from a kolin mine and is coated in a grey dust.
    I hope you can see where I have wiped off the dust on several of the coils.
    The shunt coils are marked "FJW 5AG" if that helps.
    Attached Images Attached Images      

  15. #15
    Join Date
    Oct 2008
    Location
    Madison GA
    Posts
    89

    Re: SA-250 wiring

    I haven't been on in a while and realized that I hadn't updated my progress.
    I found a complete parts machine with a good welder but stuck engine (same year and one code number different).
    I removed the armature and installed in my machine.
    Everything is now working properly and have a bunch of parts left over!!
    Thanks for all your help

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