NBC 140 Autoweld 140

TORQUEFACTOR · Feb 23, 2010

I need some advice, I have a NBC 140 Autoweld 140 which has been great over the years. I think the Main rectfier has gone but am not sure. The welder now at any settings makes the welding wire go red hot at the torch head, it does not have any power, after a few seconds the fuse blows in the mains plug are these symptoms typical of the retifier problems or is there anything else which could be faulty. I donot think the transformers are faulty, as I cannot smell any burning. If you have any info I would much be gratful regards, Torquefactor

SirDick Diodenob esquire · Feb 25, 2010

Could be one of the diodes , how many does your machine have ? I am seeing that a lot of recently manufactured machines use button type diodes , a thermal arc machine I am working on has a total of 19 of these in the main rectifier and I really hate the design , for the sake of a little more cost the maker could have fitted four good quality diodes in a set up something similar to post 10 on this thread that would have been easy to replace individually but I suppose all these companies want to make more profit . Post a photo . You test the diodes with a multimeter on resistance setting seeing if they pass current in one direction only . If you have one diode gone dead short without then going open circuit you could have the others feeding through it which could be the reason for your mains fuse blowing and reducing the current at the torch.