AIRCO 250 AC/DC Heliwelder V

I need some help from a person that knows electrical problems. I have
used welder that I am refurbishing. I have made a repair to th
interface board that had a blown capacitor. When I turned that welde
on it seemed that everything was okay with the fix so I am testing th
weld capabilities. As I don't have it set up for the tig yet, I am jus
testing the "arc" functions. When I selected AC and used a 7018 3/32
rod I was able to run a bead. When I selected DC (straight polarity) o
DC (reverse polarity) and turned the welder on it flipped the circui
breaker. The question(s) that I have:
1) Is this a dead short in the rectifier bridge? diode? If so how can
check the fault?
2) Can can check to see if the high frequency works using the "stick
Thanks for any help.
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With the machine OFF, use an ohmmeter across each of the diodes. It should read high one direction, low the other direction. If you find one that is low both ways, that's the culprit. If one reads high both ways, it is open and will need to be replaced but it is not the cause of the blown breaker. The actual readings in ohms is not correct since the diode has a voltage drop.
hd_74al wrote:
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That would be the logical place to start your troubleshooting. Watch out for reverse polarity diodes if you replace any. Reverse polarity diodes are ones that have the anode and cathode reversed in relation to the physical configuration of the unit. Look for the diode symbol on the side of them and match it up in direction with the new one.
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