Hi Guys ----This is a bit of a challenge ---sorry!!!

I bought a new combined stick and Tig. welder (thought to be a Chinese clone) I had it for one month. Used it twice and it blew up. I also have a 20 year old 90 amp AC “ buzz box “. The outer case had seen better day, but it is impossible to wear the dam thing out.

To cut my losses I decided to insert the “buzz box” working, into the new case. Adding four 150 amp diodes I converted it, to make it DC. I am really pleased how it welds, stick electrode positive. The output voltage (no load) is 68v I do not know that amperage because I only have a 10 amp multimeter.

The downside of my conversion is that I now can’t control the amperage.

My questions is ----- does anyone know of a SIMPLE circuit design, to control the amperage up to 90 amps.

 

You will get better results if you use the welder as electrode negative. This is known as DCEN, it puts more heat/penetration in to the work. For tin stuff you use the electrode positive known as DCEP. This link will explain it more for you - http://www.esabna.com/EUWeb/AWTC/Lesson2_11.htm

What happened to the amperage "taps" from the buzz box? Even with a current control you need a way to set the 'base' current. A current control, like a foot pedal on a Tig, can only control a small/fine amount of current. heres a link to a DIY one -http://aaawelder.com/reactor.html

What your looking for is called a "saturable core reactor", hers a link to a DIY one -

 

I just fixed a plasma cutter using this guys cd info.

http://www.drviragopete.com/plasma_cutter_repair.php

all That was wrong with it was a loose connector . I used the chop stick
method. poking the connectors with the end of a wood spoon until I found it! paid only $80 for the plasma cutter it was new returned item.
made out like a bandit.

 

Thanks for your help Guy's. Very interesting !!!!