Will a welder continue to work if the Power Factor Capacitor fails? What exactly happens when a transformer overheats?
I just picked up a 1954 61F. It looks like someone tried to repair it. To open the welder, the top handle needs to be removed. It is held with a cross-pin that rusts in place on all of these units. On mine, the sheet-metal cover around the shaft the handle attaches to is seriously bent on both sides, from someone trying to pound out the rusted handle pin. Then they used a grinder to cut off one side of the cross-pin and handle base, started on the other side, and gave up. Someone really wanted to open this welder, probably because it stopped working.
There are only 3 things inside a 61F: On/Off switch; PFC; and transformer. The switch is accessible through the vent opening in the back of the shell, and no evidence that someone tried to work on it. That leaves the PFC and transformer.
PFC:
Looking at the electrical schematic it seems the PFC is additional to the main wiring, not carrying all the electricity flowing through the welder. Or maybe that is just the way it looks because the PFC wiring diagram is on the same diagram as the non-PFC unit. It was built in 1954, so the capacitor is 62 years old, and they do not last forever. Hopefully that is what failed, and bypassing it will get the welder running again.
Transformer:
The welder weighs 263 lbs, and I’d guess the transformer unit is 175 lbs of steel and copper. Not easy to overheat while stick welding at 180 amps max output. (Miller Thunderbolt or Lincoln AC-225 at 225 amps, same 20% duty cycle, are only 110 lbs for the entire unit). There is no fan or thermal overload switch. It is cooled by convection, which explains the low 20% duty cycle for a welder this size (and weight).
What exactly happens when a transformer overheats? What damage is done, and what will happen when I attempt to power it up again? Is there any way to tell if it is damaged before doing all of the steps below?
Examination & Restart:
Once I finish drilling out the handle and get the cover off, I will vacuum out all the dirt.
Disconnect the PFC and look for wiring problems: arcing, corrosion, failing insulation, etc.
Clean all electrical contacts.
Clean the transformer jack screw and guides.
Set the transformer to its lowest setting and plug it in.
If nothing bad happens, crank the transformer to its highest setting.
At that point is there anything I really need to do, or just plug in the leads and see if it welds?
I do have a multi-meter, but with such a simple welder, there is not much to diagnose.
This is the first time I have opened up a welder, so I am a bit nervous. But the 61F supposedly has one of the smoothest arcs of the small AC units, and it is an interesting piece of Miller history.
Thank you for your help.
Stefen
Image 1: 61F transformer. 180 amps max, 20% duty cycle. (same as mine)
Image 2: Lincoln AC-225 transformer. 225 amps max, 20% duty cycle.
Image 3: 61F transformer, close-up.
Image 4: 61F wiring diagram.
I just picked up a 1954 61F. It looks like someone tried to repair it. To open the welder, the top handle needs to be removed. It is held with a cross-pin that rusts in place on all of these units. On mine, the sheet-metal cover around the shaft the handle attaches to is seriously bent on both sides, from someone trying to pound out the rusted handle pin. Then they used a grinder to cut off one side of the cross-pin and handle base, started on the other side, and gave up. Someone really wanted to open this welder, probably because it stopped working.
There are only 3 things inside a 61F: On/Off switch; PFC; and transformer. The switch is accessible through the vent opening in the back of the shell, and no evidence that someone tried to work on it. That leaves the PFC and transformer.
PFC:
Looking at the electrical schematic it seems the PFC is additional to the main wiring, not carrying all the electricity flowing through the welder. Or maybe that is just the way it looks because the PFC wiring diagram is on the same diagram as the non-PFC unit. It was built in 1954, so the capacitor is 62 years old, and they do not last forever. Hopefully that is what failed, and bypassing it will get the welder running again.
Transformer:
The welder weighs 263 lbs, and I’d guess the transformer unit is 175 lbs of steel and copper. Not easy to overheat while stick welding at 180 amps max output. (Miller Thunderbolt or Lincoln AC-225 at 225 amps, same 20% duty cycle, are only 110 lbs for the entire unit). There is no fan or thermal overload switch. It is cooled by convection, which explains the low 20% duty cycle for a welder this size (and weight).
What exactly happens when a transformer overheats? What damage is done, and what will happen when I attempt to power it up again? Is there any way to tell if it is damaged before doing all of the steps below?
Examination & Restart:
Once I finish drilling out the handle and get the cover off, I will vacuum out all the dirt.
Disconnect the PFC and look for wiring problems: arcing, corrosion, failing insulation, etc.
Clean all electrical contacts.
Clean the transformer jack screw and guides.
Set the transformer to its lowest setting and plug it in.
If nothing bad happens, crank the transformer to its highest setting.
At that point is there anything I really need to do, or just plug in the leads and see if it welds?
I do have a multi-meter, but with such a simple welder, there is not much to diagnose.
This is the first time I have opened up a welder, so I am a bit nervous. But the 61F supposedly has one of the smoothest arcs of the small AC units, and it is an interesting piece of Miller history.
Thank you for your help.
Stefen
Image 1: 61F transformer. 180 amps max, 20% duty cycle. (same as mine)
Image 2: Lincoln AC-225 transformer. 225 amps max, 20% duty cycle.
Image 3: 61F transformer, close-up.
Image 4: 61F wiring diagram.
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