AIRCO 250 AC/DC Heliwelder V

[hd_74al]

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
function?

Thanks for any help.

A

 

[Mike Berger]

It doesn't indicate a dead short. A 250 amp bumblebee welder draws
a hefty initial current. What kind of circuit do you have it plugged
into?

 

[hd_74al]

Mike: The AIRCO 250 AC/DC welder is single phase 220v, nothing rea
special on this part of it. After I posted this I took the Bridg
rectifier out of the welder to test the power diode and the SCR's. Thi
welder has two SCR's (hockey puck style) mounted in the aluminum hea
sink.

Here's were I need some help. I tested the power diode with
multimeter and only got a reading one way. That should mean that th
diode is okay?

To test the SCR's I used a 12v car battery, a 12 volt light and mad
two connections from the positive lead; one with a resister (1k 1/2W
to trigger the gate (white lead) and the other with a resister (100
2w) to the device (red lead). The negative lead was to the metal cas
of the device. With the connections intact I took the one lead (white
and was able to get the lamp to light but not stay on. It should sta
on with a good SCR, correct?

The other SCR did not light at all. Am I on the right track?