View Full Version : Does Anyone know anything about really old welders?
04-10-2006, 05:04 PM
I have a Military Surplus portable welder made in 1953, with a 6 cyl Chry Industrial motor. I got the motor running OK, but the welder won't put anything out. I have reworked all the brushes, (11 of them) and cleaned all the slip rings. It worked when it was parked by my Dad 20+ years ago. I only have about 2 volts AC in the (internal) exciter circuit. I am mainly testing it by checking the 110V generator part.
The unit was made by "Electric Arc, Inc." in New Jersey, and the actual generator part says "Star-Kimball/Meihle Printing Press Co.". I don't have any operating instructions, so I may not be checking it right.
My question is: Does this unit need to have the field "flashed" or anything like that since it has been setting so long? Also, can I test a welder by just checking for about 40 VDC? Anything else that I could test?
Thanks in advance!:waving:
04-10-2006, 07:03 PM
Sorry no help on your problem. I was going to post a note about this 70 year old welder I am learning from.
Now if he could just remember to close his fly after taking a leak I might have more confidence in what he is teaching me. LOL!
04-11-2006, 10:11 PM
If the exciter has lost its residual magnetism yes it will have to be re-magnetized. I know it can be done but I am not the one to expain the exact procedure. Anyone with DC generator experience could or if you are up to some research any old Automotive generator repair manual will give you the basics. It is important to figure out the arrangement of the field windings and the exciter circuit.
04-14-2006, 01:11 PM
04-28-2006, 11:15 PM
it somewhat depends on what kindof exciter you have.if its a permanent magnet type exciter the magnets may be dead/reduced in field strength or they may be backwards if you took it apart and didnt get the correct polarity. magnets can be recharged but not many places can still do that. if its a self-exciter like some older 'generator' or even some alternator types - a very small amount of residual magnetism can be used to get it to start and then it builds its own field strength quickly as it turns. the exciter is probably a typical wound rotor generator in that respect- this exciter generator makes the exciting (rotor)current for the main welder and controlling it is used to vary the amount of power the welder creates. if you are only getting 2V after its running for 2-3 seconds and its supposed to be this type, then you have a wire or component problem in the exciter because its not building field strength nearly fast enough -should probably have full field in a few seconds after it starts. if you take it to a welder repair shop they will be able to tell you what kind of exciter it is and whats wrong with it probably quite easily but maybe for a fee. with no docs on it- you are reverse engineering something and you need to know 5x as much more about than if you knew what it was and what its components were supposed to do.
05-03-2006, 12:26 PM
lucywalker- Thank you very much for replying. I haven't had the generator apart, and it worked when my Dad parked it 25 years ago (where have I heard that before!). The tag on the generator says it's a "DC Generator". One of the 4 main winding wires that comes out is connected back through an odd (9th) brush at the comutator. I think that is the exicter. BTW, I recently found out that the field may not build back up if there is a load connected. Dumb me! I've had a 100W shop light plugged into it during all my testing! I'm going to take another run at it with no load and see what happens. Do you think it would hurt if I briefly connected, say 6V to the 9th brush to see if that would do anything?
05-10-2006, 08:45 PM
I recall that with old auto generators that wouldn't self excite, you had to get it up to operational speed, then connect a charged battery across the output with the correct polarity. This provided the safest initial excitation and it would self excite when run after being subsequently shut down without reconnection the battery.
The typical Q&D method was to zap it with the battery when it was not running. It was a little harder on the armature because it behaved as a dead short. So long as the field winding got some juice, it would hold enough of a residual field to self excite. In the repair shop they would excite the field on its own without the armature, then assemble the weldor.
For the weldor I would probably just use a 12 volt battery for a short time. If all is well the weldor should re-excite and go up to it's full potential of 24 to 50 volts. At that time you don't want the battery in the circuit because it could be seriously overcharged.
12 Volts should not do a spinning weldor any damage. If it doesn't run after a try or 2 it should be looked at by a repair shop
05-11-2006, 09:32 AM
Tech-ad- Thank you. I will try that soon. There are 4 wires out of the field. Should I connect the 12V across any 2 of them? Or should I use the case as ground and pick one at a time? BTW, the tag on the gen says it's output should be 40V.
05-11-2006, 08:09 PM
My '47 Lincoln SAE300 has only two brushes for the exciter. One on top, and one on the bottom directly opposite from each other. I guess you could connect the battery to two that are opposite from each other, one neg and one pos that way the voltage is equally distributed.
Lincoln SA-200 welders use a 4-wire exciter field. One winding, the shunt field, is made from fine wire and connects between the two exciter brushes. The other winding is made from heavier wire and connects in series with the load. To flash one of those, you must lift one brush off of the commutator, and put DC power across the exciter brush terminals. This is, of course, done with the engine off. If you flash the exciter while the engine is running, place a DC voltage across the exciter brush terminals without lifting a brush. If you decide to try this method, it would be wise to use a diode between the exciter and the battery to prevent exciter voltage from getting back into the battery. Exciter voltage can often be much higher than weld voltage. Some Lincoln DC exciters can produce as much as 165 Volts. I would be concerned about the battery exploding if the exciter built-up and applied that much voltage to it.
Please be extremely careful when working on any of these machines. The high voltages they can produce can be very dangerous.
I hope this is helpful in some way. Good luck!
vBulletin® v3.8.7, Copyright ©2000-2013, vBulletin Solutions, Inc.