HF welders also don't have the electronics Lincoln's and Miller's do. It's just a cheap welder that's light enough to climb ladders and scaffolding in hand. I do prefer the old Ideal Arc welders myself.

After getting under the hood, I realized this machine is just a large, old power supply. It has a multi-tapped transformer, diodes, inductors and capacitors to smooth the wave form. It is very inefficient by today's standards. I'm thinking since the inductor is welded on top of the transformer because it is borrowing some magnetic flux to keep the amperage surge down?

The Lincoln Weld Pac 100 I have adds an electronic board and capacitor the HF doesn't have. Since the Lincoln no longer functions, I'll rob the capacitor. It is a DC 59,000 uf cap, so care must be taken to get the connections right.

I found adding capacitance works great if you run Flux core.

Flux core or stick is all I do. I should get that mod done tomorrow.

My test equipment shows this 40 volt 59,000 uf capacitor at 34,000 uf, which is out of range. I'm going to get another capacitor. There's small difference between the before and after sine wave. It was added before the inductor on the positive side and negative goes directly to the negative side of the lead. This is supposed to be a DC signal so its very very rough.

Use both.
I found that Flux core likes as much capacitance as you can throw at it.
Welders use the default 50k to 60k uf capacitor as a good trade off between solid wire and Flux core performance. With the trade off favoring solid wire and gas.
With nearly 100k uf I can make Flux core welds that are as good looking as solid wire and gas.

I know this thread is a little old, here's another option to consider if the heatsinks do not provide enough cooling: https://www.geek.com/geek-cetera/coo...n-oil-1495403/
Take the fans out and submerge in a 5gal bucket of oil....? Just don't kick the bucket!

Maybe it a factory or shipyard, where they need continuous-duty welders.?.

patrickh99, I have considered liquid cooling but the welder has to be kept as light as I can get it. The welder frequently goes up ladders and scaffolding in my hands.

The heat sinks are working very well. They keep the welder about 30 degrees above ambient temp now.

I ordered 4 capacitors several weeks ago on ebay. They came in and I tested them before instillation. I'm glad I did. They tested out at about 10% of the face value. The seller issued a refund and I'm still hunting for suitable capacitors. They're difficult to find without spending $80 each.

What specs are you looking for on the caps?

Somewhere around two 47,000- 97,000 uf electrolytic capacitors. Screw tops are preferred as it would simplify installation but not absolutely necessary.