Hobart GR-303

[liston336]

I have a Hobart GR303 powerweld with In-line 6 engine.
It starts and runs great. (low idle / high idle switch working).
It has no output( weld , aux., etc.) so since it has been sitting awhile I figure it has lost it magnetism in the rotor. I need to flash it, so can someone advise me on the proper way.

[lars66]

The FIRST thing to check is make sure ALL the brushes are loose and free in the holders and the springs have tension.

[old fart]

The GR-303 has a built in flashing circuit unless you have a really old one.
There is a small board behind the panel near the keyswitch with a fuse on it. Check that fuse. Another test, if you have a voltmeter there should be battery voltage between the center slip ring and ground during engine cranking. To manualy flash, temporarly connect a battery between the center slip ring and frame of machine.I stress the word temporarly, if the voltage builds up with battery connected it will melt wires cause explosions and really wreck your day. Good luck. O.F.

[liston336]

The FIRST thing to check is make sure ALL the brushes are loose and free in the holders and the springs have tension.

Lars66,
That was the first thing I checked.
Thanks liston336

[liston336]

The GR-303 has a built in flashing circuit unless you have a really old one.
There is a small board behind the panel near the keyswitch with a fuse on it. Check that fuse. Another test, if you have a voltmeter there should be battery voltage between the center slip ring and ground during engine cranking. To manualy flash, temporarly connect a battery between the center slip ring and frame of machine.I stress the word temporarly, if the voltage builds up with battery connected it will melt wires cause explosions and really wreck your day. Good luck. O.F.

Old Fart,
That sounds like a plan to me. I am going to rig me up a flashing device/ box to make sure I can prevent the bad day.
Thanks, Liston336

[liston336]

Hey everyone,
I am just getting back to figure out the problem. I assume the built in flashing circuit you were speaking of is labeled DBR on the Hobart drawing. I have not removed it to check for a fuse. I did try to flash the welder with a 12 VDC battery charger, but to no avail. There are so many connections and componets corroded, I just statring ohming out wiring. I removed the VC board due to the fact I read both ways on a diode which went between the + and - on the generator revolving field. Can a brother get some more input? thanks Liston 336

[Pin Head]

Checking the resistance of wires isn't all that effective because unless a wire is broken and has no resistance, you may not be able to tell whether a circuit is good or bad. A 1 ohm resistance may be a big problem for a 300A circuit and you need a very accurate ohm meter to tell the difference between good and bad. It is easier to fire it up, put a load on it (like a carbon pile) and look for a voltage drop at all the connection points in the circuit. If you have a big voltage drop between two points, you may have a defect between the two points.

You can get fooled checking a diode with a meter if you don't remove it from the circuit first. The current could be flowing through a different path than the diode if it is still in a circuit.

[liston336]

Checking the resistance of wires isn't all that effective because unless a wire is broken and has no resistance, you may not be able to tell whether a circuit is good or bad. A 1 ohm resistance may be a big problem for a 300A circuit and you need a very accurate ohm meter to tell the difference between good and bad. It is easier to fire it up, put a load on it (like a carbon pile) and look for a voltage drop at all the connection points in the circuit. If you have a big voltage drop between two points, you may have a defect between the two points.

You can get fooled checking a diode with a meter if you don't remove it from the circuit first. The current could be flowing through a different path than the diode if it is still in a circuit.I found a shorted diode in the DBR (Diode Bridge Rectifier) Mounted on the front panel. By the schematic I have it excites the aux. generator and drives the voltage control board for the welding generator. I also found a transistor on the voltage control board with a broken lead.

[Roadhse2]

I *think* i have the same welder...mine has a 115v AC outlet and 3 slip rings...the whole thing has been painted over in the past so i have no identifying numbers etc...it too, will not arc when started...Ford inline 6

I was wondering if i could find out where you got your schematic? It was working before i bought it...sat a year or so and now will not work...i havent tried flashing yet, but will....the schematic would be very helpful

Thanks, Glen
Roadhse2@yahoo.com

[liston336]

I *think* i have the same welder...mine has a 115v AC outlet and 3 slip rings...the whole thing has been painted over in the past so i have no identifying numbers etc...it too, will not arc when started...Ford inline 6

I was wondering if i could find out where you got your schematic? It was working before i bought it...sat a year or so and now will not work...i havent tried flashing yet, but will....the schematic would be very helpful

Thanks, Glen
Roadhse2@yahoo.com
I purchased a manual from Miller Archive dept. I can email or fax you a schematic. If you want a copy I will need to scan it some how.

[Roadhse2]

An email would be great...Roadhse2@Yahoo.com

Thanks!

Glen

[Roadhse2]

Could you tell me how to find the Miller Archives dept, so i can order a manual? I have found some burnt diodes, but have no idea which replacements i need so would like to purchase the manual/schematics for this machine.

Thanks, Glen