Hobart G310 gas welder cuts out after 30 seconds running--anyone have an idea?

[therrera]

Hi all,

I have an old thread on this machine that I started in order to identify it and then to get her running. A member was able to identify it as a G310 and sent me pictures of his unit plus the wiring diagram for it. I started this new thread focusing in on the current problem so that it might attract the attention of new members who could lend a hand.

This machine is an AC-DC generator welder that has both 110v and 220v plugs. The engine runs but it only produced tiny sparks and no welding current or at the AC outlets. A retired repairman looked at it and was able to get it to generate AC power to the plugs but it cut out after 30 seconds or so. I think he told me it was wired incorrectly. Also I installed new brushes and cleaned the stator rings.

I am hoping that someone out there recognizes the symptom and can suggest a course of action. The fact that the machine produces current tells me that the major components are good (armature, stators, field windings, etc.) and that the problem may be from one of the circuits (a resistor or diode, etc.)

Anyone have a clue what could be causing this erratic behavior? Attached is a picture of the g310 the member sent me. It is identical to mine.

Thanks ahead of time for your help,

Tony

[jetoneusaf]

Hi Tony,
Speak of the devil,I have exactly the same model welder you have, i have used it off and on for 15 plus years, it always started good and just seemed to run forever, I was welding with it today , running some hot passes , I stopped to get a drink of water, when I started it again it would not strike an arc and the a/c 110 220 outlets were inop, I get no amps /volts indicated on the gauges , if i contact the rod to the ground i just get a very weak spark. Guess we are in the same boat, hope you have figured yours out by know and have some wisdom to pass on, If I find any good info ill pass it on, look forward to a reply Andy @ jetoneusaf@gmail.com

[canoecruiser]

Troubleshoot it from the commutator on back. Start with the brushes. Alternators that don't get excitation current to the armature can generate a small amount of power by self-exciting. Using a voltmeter, see if you get any voltage at the brushes. If yes, check the brushes; also examine the commutator to see if they are worn down below the insulating members between them. When the commutator bars wear down to the insulation they will arc a lot due to the brush not seating well on the commutator bars. This accelerates brush and commutator wear.

If the brushes and commutator are good and you get excitation voltage at the brushes, work your way back and look for loose connections and dirty contacts. The above will usually fix 90% of what goes wrong when the symptoms are as you described. It can happen all of a sudden....it works and then you put a new stick in the holder and it doesn't. If this does not resolve the problem then a schematic and troubleshooting specific to the units design is needed.

When you do find the problem, post how you found it and what the repair entailed. This will add to the body of knowledge that others can draw on.

Good luck.....

Quick edit: It goes without saying but it's worth saying, be really careful when working around rotating and/or electrically-live machinery. Like traffic crashes it just takes a second of "not paying attention" to ruin your day, or life.

[jetoneusaf]

Pulled the hat and cked the brushes, a couple were short and it looks like some on has subbed some in before that werent the right width. one commutator ring is just plain black ( arcing i assume) will clean them up and put all new brushes in when i can locate them , had no luck on a part number or source for brushes yet, still need a good line on a manul, hobart appearently sold the line on the big stuff a number of years a go, picked up a tip from an old repair man and he suggested checking the amperage rotary adj handle, max and fine, did the fine (cleaned it up , nothing apearent, still need to do max) will test as soon as i can locate/install new brushes thanks guys! Andy

[urch55]

Pulled the hat and cked the brushes, a couple were short and it looks like some on has subbed some in before that werent the right width. one commutator ring is just plain black ( arcing i assume) will clean them up and put all new brushes in when i can locate them , had no luck on a part number or source for brushes yet, still need a good line on a manul, hobart appearently sold the line on the big stuff a number of years a go, picked up a tip from an old repair man and he suggested checking the amperage rotary adj handle, max and fine, did the fine (cleaned it up , nothing apearent, still need to do max) will test as soon as i can locate/install new brushes thanks guys! Andy

See if you can find something here....
http://www.carbonbrush.com/hobartbrush.htm

[therrera]

Thanks for the tips fellas,

I will start undoing and cleaning all the connections I can get at. Together with a friend we checked the stator rings and I polished them with fine sand paper and put new brushes in some time ago. We eliminated that the armature and field windings were shorted by putting an ohm meter between the wires connecting them and ground. On the stator rings we put the meter on them and grounded to see if there was continuity (a short) but there was none.

One of my friends suggested that one of the diodes may have gone bad. The symptom I get is also light sparking when trying to strike an arc. The report of my machine cutting out after 30 seconds was incorrect. I had a repair man with electrical savy take a look at it and he reported that one of the gauges (voltmeter or ammeter, I don't know which one) showed current flowing and then cut out. However when he brought it back to my place the gauges showed no movement, so he must have been mistaken. Anyway he found some disconnected wires at the remote plug and per the schematic for the machine, connected them but it made no difference.

I think we eliminated the heavy, expensive type of repairs (armature and field windings) so whatever the problem is should be relatively minor.

Sorry I have not replied sooner, I failed to set the instant notification option so only be logging on was I able to see that I had received replies.

Thanks,

Tony