I'm trying to troubleshoot an electrical issue with my 1966 Lincoln Idealarc 250, and I'm not sure what to try next. Here is what I know:
If I touch the work clamp without gloves and the welder set to AC, I get a shock.
If I switch my welder on when my metal work table is connected to AC ground AND my welder's work clamp, the welder sounds like it's under load.
When switched to DCEP, the potential difference between the work clamp and AC ground is 82V, the same as the difference between the work clamp and the electrode.
When I opened up the welder and disconnected the wires from the big capacitor, there was no continuity between the capacitor terminals but there was continuity between the two wires. (I assume this means the capacitor's fine, but there's a short elsewhere.)
Other than the problems mentioned above, the welder works great. I would like to solve this so I can properly ground my welding table and avoid getting shocked again.
I don't know what's inside that machine but it sounds like there is a short between the welding circuit and mains ground.
Assuming the case is grounded (connected to mains ground), your open circuit voltage of 82V will appear (probably) between the return clamp and the case (or mains ground).
It is a matter of finding where that is happening.
jbd wrote: ↑Wed Apr 10, 2024 9:51 pm
[*] If I touch the work clamp without gloves and the welder set to AC, I get a shock.
Does this happen even if there is no arc initiated?
Check the internal lug connector for the ground clamp. Make sure it has not come loose. If that appears ok, I'm with Jack, you've got a deeper issue that might require a drop-off to the Service Repair shop.
Jack Ryan wrote: ↑Thu Apr 11, 2024 3:31 am
I don't know what's inside that machine but it sounds like there is a short between the welding circuit and mains ground.
Assuming the case is grounded (connected to mains ground), your open circuit voltage of 82V will appear (probably) between the return clamp and the case (or mains ground).
It is a matter of finding where that is happening.
I have a schematic from Lincoln but I'm not sure if I can share it. There's a big "Proprietary & Confidential" warning on it. This is what the inside looks like: https://weldingweb.com/vbb/attachment.p ... 1311653472
I have the case open and I'm checking continuity. The case is connected to mains ground, but I can't find any spot where the welding circuit is connected to the mains ground. Maybe I'm missing something.
I'm seeing 32V between the return clamp and the case (and 82V between the return clamp and electrode).
jbd wrote: ↑Wed Apr 10, 2024 9:51 pm
[*] If I touch the work clamp without gloves and the welder set to AC, I get a shock.
Does this happen even if there is no arc initiated?
Check the internal lug connector for the ground clamp. Make sure it has not come loose. If that appears ok, I'm with Jack, you've got a deeper issue that might require a drop-off to the Service Repair shop.
Yes, it happens even if no arc is initiated. The internal lug connector isn't loose.
I'd really like to troubleshoot and fix this myself if possible. Any other ideas for what to check?
the first thing i would check is the earth circuit of your house and the welder. then check the neutral side.
i don't know your guys power system over there but it sounds like you don't have a 0v reference ie the earth or neutral. that can make the welders ground plane increase in voltage and shock you because its higher in voltage than you are.
having a look through some pics, i see the incoming earth is clamped between the cover and body, which is a dumb idea. make a proper earth post.
check the suppression cap above the fan area. it looks like that might have an earth connection. hard to tell from pics.
edit: looks like a suppression cap? on the inside the front cover which is connected to earth.
