Converting AC buzz box to DC & other q's

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My neighbor just drug home a sparkling new sexy red AC 225 from his Churches basement.  Adjustment knob was busted so it was no worky. We got it apart and fixed it after some monkeying. It had been bought by a maint man and set up by him. First thing I noticed was the leads were backwards. Ground Clamp was the longer and thicker cable that went  inside to the adjustment switch.  The stinger was short and  to the bottom of the block inside.  It had been used like this it's entire time at the church, he fixed some dumpsters, made some big boxes for roofing tar and repaired some of the old iron hand rails.  I laid some beads down in this configuration and it seemed funny, real puddly, all over the place. I guess this is some sort of reverse polarity flavor of ac welding if your ground clamp is carrying the heat to the work and the rod is grounding and completing the circuit. I switched the leads and it lays down a very strong arc, better than my old Lincoln ever did.  I wonder if there is any possibility of damage from being run this way.             Also I searched and couldn't find any info on how to get DC capability  out of an AC only arc welder. I read  where people did this but no hints at a ready made kit which is more or less what I would like, for my neighbors machine and my old lincoln now in my older bro's care.  I would think there would be a good market for a converter kit that an average joe could install. Tell me what I need to do this safely, any links would be great.
Reply:I tried this with a huge 400 amp full wave bridge rectifier I found in some salvage, it did not work very well on my AC stick welder, I think the voltage ended up too low as it was hard to get the arc going and to keep it going had to keep a real close arc, then it wanted to stick.  I ended up blowing the bridge up as I tried to crank the welder up. A diode in the bridge the size of a hock puck went off pretty good, think of firing a 308 rifle inside the garage.Lincoln PT185 TIGLincoln 175 MIGLincoln 240 amp AC StickLind Needle Arc plasma welderPlasma cutter, soon???
Reply:Any device made of semiconductor material has to have a good heat sink and a way to get rid of heat. Semiconductor material is one of the few materials whose resistance goes down when they get hot, instead of the other way around. This leads to what is called thermal runaway.The newer DC welders have some features that make them superior to a simple DC welder. My Thunderbolt, for instance, can sense a low arc voltage and boost it up to keep you from sticking the rod. This is something a welder like me can really appreciate.
Reply:AC out of a buzz box has no poarity, so flipping the leads should change nothing, maybe something else happened at the same time? Bad connection, or corrosion/dust in the dial contacts ect?I would think anything that needs DC welding likely needs to be done right and at that point a rigged up bridge is not likely to give the results.Lincoln PT185 TIGLincoln 175 MIGLincoln 240 amp AC StickLind Needle Arc plasma welderPlasma cutter, soon???
Reply:http://www.proto-power.com/dc_cheater.htmlWorks well with only a small loss in power, and you can reverse the polarity if you need.There are no small projects
Reply:I was wondwering if those were still available. I see the name had changed. They used to be called a DC converter. I have one that is around 40 years old and it is still going strong. The only moving part in it is the cooling fan.
Reply:Thats what I am talking about right there. Perfect little kit, sorta high but worth it. I'll be passing that on to some folks. Thanks for the link imagineer!!     I am not really keen to rig up anything sketchy. Thats what I kept coming across when I googled it, somebodys homemade super sketchy set up.
Reply:'Sketchy' is my middle name.     Actually it's 'Danger', but that's a long story...I too was put off by the overall cost, but after pricing out all the components separately, it was only about 16% more to buy the kit.There are no small projects
Reply:i built a rectifier bridge from four big diodes i found on Ebay and an a/c capacitor.  It did pump out some heat and I installed a cooling fan but it worked very well.  I did a lot of good welding with it.   It was a fun project but if i consider my time worth anything, I'd have done better to sell the old buzz box and buy an AC/DC machine.
Reply:That's not a bad price at all for the capability you get. I have let my neighbor burn rods on my Thunderbolt and he really liked the DCEP setting. To him it is really his churches welder even though they gave it to him and it was no worky. He wants to do some repairs on the old handrails at the church when he gets comfortable enough with his skill. He layed down some nice beads with very little instruction and has been reading  all my old welding books.               I read enough to know that it's over my head to be monkeying with diodes, rectifier and bridges. It's greek to me and the little DC Cheater seems simple enough.