Old Airco Welder becoming Safety Hazard

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Hello Everyone. I am a college student, and I bought an ancient (Circa 1965) Airco welder a few years back. I have used it a lot for TIG and stick, and it has worked very well for me. Unfortunately, in the last few weeks I've been getting shocked by the ground clamp when I have the machine on DCEP and DCEN. I checked the voltages and here's what I got45v from Work clamp to ground --> 45v from ground to stinger on DCEP-45V from work clamp to ground --> -45V from ground to stinger on DCEN0V from work clamp to ground on AC I double checked by wiring from the wall and everything checks out. I have attached some pictures of my setup and a circuit diagram for everyone to look at. If you know of any possible causes for this and remedies please let me know. The machine still welds beautifully and I just did a big aluminum fabrication project on AC tig where didn't shock me at all. DC is the issue. I would really hate to sell this machine for scrap, I learned to weld on it and have made some cool stuff. But if it is a safety hazard I'm not willing to get electrocuted to save a 60 year old machine.




Last edited by sbmarcom248; 6 Days Ago at 11:31 AM.
Reply:I have a similar welder (Miller 330AB/P) that behaves similarly (never checked it on AC, though). I think I get maybe 15VDC from the leads to ground.I'm just careful to wear gloves and boots (or rubber-soled shoes) when using it. Probably not what you wanted to hear, but...
Reply:I just went out and double checked the voltages, and on the DCEP setting there is 220V AC across the leads in addition to the 45V DC. No wonder I'm getting such nasty shocks.
Reply:SB, you may want to check your transformer connections, also where the main line comes into the machine. Does the machine have a good equipment ground connection coming from your main service?
Reply:

Originally Posted by sbmarcom248

I just went out and double checked the voltages, and on the DCEP setting there is 220V AC across the leads in addition to the 45V DC. No wonder I'm getting such nasty shocks.
Reply:Yeah the ground is fine, I checked the resistance from the plug to the panel this morning and it was 1 ohm. I'll pull the machine away from the wall and check my main connections. And yes it was probably 240v, the multimeter was fluctuating a lot but it was around 120V from each terminal to ground.
Reply:

Originally Posted by sbmarcom248

Yeah the ground is fine, I checked the resistance from the plug to the panel this morning and it was 1 ohm. I'll pull the machine away from the wall and check my main connections. And yes it was probably 240v, the multimeter was fluctuating a lot but it was around 120V from each terminal to ground.
Reply:Well everyone, I found the issue. The balancing resistor switch had fallen down and was just barely touching the frame. This was sending power to the ground clamp. I riveted the switch back on the frame and now it is acting just like it should. If you look right below the top contact on the switch you can see a little black mark where it must have been arcing.I really appreciate the responses, I'm glad it was such an easy fix.


Reply:enough leakage to ground to shock you but not enough to trip the breaker... good that you are going to check your ground system.
Reply:

Originally Posted by jmm03

enough leakage to ground to shock you but not enough to trip the breaker... good that you are going to check your ground system.
Reply:

Originally Posted by sbmarcom248

The machine is on a 100 amp breaker so no surprise there. I went through the circuit pretty closely this morning and everything is on the up and up with the grounds.