Been practicing on some aluminum...

Been trying to learn how to weld aluminum lately with my old Airco and I think that I'm slowly getting better. All these beads look a little cold to me but I currently only have a 17-Series 150A air-cooled torch. I had the current on the machine set to 180A but I was reading through the manual for my welder and realized that the POT in the foot pedal is supposed to be a 10KOhm where-as I installed a 25KOhm POT when I refurbed the pedal and I think it's effecting the welder's output. The reason I installed a 25K POT was because that's what the old one speced out as but yesterday when I had the side panels off my welder blowing out the dust and setting the high-freq spark gap I noticed that somebody had made an adapter to go from the original rectangular 6-pin Airco connector to a round 6-pin Hobart/L-TEC connector and these welders used different POTs in their pedals. So that POT is something I need to change and see if things work differently. Anyways, here are the pictures of the beads I've been running the last 2 days. Just trying to get as much seat time as I can. These beads are much nicer than what I was doing a couple of weeks ago. Ha!

Attachment 8441Attachment 8436Attachment 8437
Attachment 8438Attachment 8439Attachment 8440
Attachment 8442

Settings were as follows.
Current: 180A on panel controlled with the pedal.
Tungsten: Pure on some 2% Lanth on others. Both prepared with a taper with a flattened tip instead of a point.
Cup: Flat Stock: #8 Small Gas Lens; Fillet: #6 Small Gas Lens
Torch: 17-Series Air Cooled
Gas: 15-17CFH Argon
Post-Flow: 12-15s

They do look a little cold. The corner joint looks pretty good. How did the back look? If your Airco has separate panel/remote switches for the current and the contactor, you could set the current to panel, and just use the pedal for the contactor switch. Then you could see if the power is the same as what you got with full pedal. Lots of old welders have been modified in many different ways. You may have to look around to see if there are other mods to make that pedal work properly. Did yours come with a schematic?

Yeah I have a schematic. The pedal hooks into the only pc board in the welder and the board doesn't look modified. The the board controls a "DC Control Coil" as the schematic says and that adjusts the output.

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Originally Posted by Rambozo

They do look a little cold. The corner joint looks pretty good. How did the back look?

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I am with you on that. They look like nice welds but don't seem like they have a lot of penetration. Flip them over and see if you see lines where you welded.

Are you making a puddle and dipping the filler in it or heating the filler???

Making a puddle and dipping the filler into said puddle.

Yesterday I think I found another issue with my welder. The current in my welder is controlled by a saturable reactor and the DC coil in that reactor is fed by an 80v transformer varied through a TRIAC then converted to DC through a small bridge. Yesterday I discovered that bridge is letting a significant amount of AC voltage through it. I removed it from the welder and tested it on the bench. I got on allied electronics and ordered a new bridge along with the correct POT for in my foot pedal and hopefully this will cure the little issues I'm having with my welder. Unstable arc in HIGH range on AC(DC arc is quite smooth but on DC there is a large inductor that smooths out the current variations), not a lot of cleaning action when in AC, and the fact that I can hold a sharpened point on a PURE tungsten at 150A on AC on a transformer machine! In fact it barely melts the point off when I have the machine set at 200A(I'm not reaching full power because of the foot-pedal POT) but from what I understand a transformer machine shouldn't hold a point on a pure tungsten on AC very well. Tungsten size has been 3/32".