February 03., 2007

The attached 7 pictures illustrate the conversion of a Lincoln 225 Amp AC 
"buzzbox" welder to a fully functional DC TIG welder.

Pic. #1 shows the front panel with the high current banana plugs and jacks.
Pic. #2 shows the internal frame added to the cabinet to mount the inductor 
and heat sinks.
Pic. #3 shows the inductor with the diodes and their heat sinks.  A small 
fan blows air through each            duct.  One end of the inductor winding 
is visible at the lower right of the pic. 4 conductors           are run in 
parallel and the ends soldered together.  Note that the heat sinks are 
electrically          isolated from the inductor iron.
Pic. #4 shows a view of the high frequency arc starter.  The oil burner 
ignition transformer is located         at the front left.  The spark gaps 
are at the front right.  The electrodes are 1/4" dia.                
tungsten carbide shanks oss broken end mills.  The spark gap is set to 
..008".  At the right             rear is the coupling transformer which 
superimposes the high frequency arc starting voltage             onto the 
welding current.
Pic. #5 shows the gas-cooled tig torch tip, and a home-made banana plug. The 
plug tip is 3/8" dia. x            3/4" long.  It is turned for a close fit 
in the reamed banana jack hole prior to slitting.
Pic. #6 shows the foot pedal current control.  The white box contains the 
potentiometer only.  The              triac current controller is located in 
the welder cabinet.
Pic. #7 Shows the circuit diagram of the triac current controller.  This 
circuit was extensively bench          and "production" work tested.

Note:  Although not shown in these pictures, it is of primary importance 
that the bridge rectifiers be shunted, or by-passed, with ac service 
capacitors of about 16 micro-farads capacitance.  This is to protect the 
rectifiers against the high voltage from the arc starter.  Without these 
capacitors the rectifiers will let out the magic smoke and become useless 
ie. they will burn out with the application of the arc starter voltage of 
5000 to 10000 volts.

Wolfgang F. Habicher