SA-250 Troubleshooting

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Does anyone have any information on trouble shooting the shunt coils and the exciter coils? I also understand they have a rotor instead of an exciter armature. Is there any way of testing those as well. Any information will be a help. The machine quit welding, cleaned the exciter commentator, pulled the brushes and put them back in and will not even run a grinder. Thanks Mike
Reply:60,The SA-250 - as you've indicated - has an alternator that provides the welding generator field current.  The AC from the alternator is converted to DC by a full wave bridge rectifier and then supplied to the welding generator shunt coils thru the fine current control.The bridge rectifier and exciter circuit is protected by a 15A fuse so, the place to start is there and if OK then check the bridge rectifier for one or more shorted or open diodes.If the rectifier is OK then check the Fine Current Control rheostat to make sure it doesn't have burnt windings or ??.The main shunt coils of the SA-200 have a resistance of ~40ohms between the blue and brown shunt coil wires and would presume the SA-250 are approximately the same.Back to the alternator rotor, I do not know the specs on its resistance but you could still check for open windings between the slip rings or for shorts between each ring and the rotor shaft/frame wit an ohm meter.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Thanks for the insite on the 250's, I did find the problem and fixed it. The spring on the main brushes was kicked over for some reason and wore the brushes uneven. I made a gamble and changed all the brushes and fixed the problem. Thanks for the reply
Reply:Good deal and thanks for the update.  Brush must have hung up and lost contact.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!