SMAW/Stick machines - options?

[Nutfarmer]

What I am using is a Lincoln ideal arc 300 that I purchased new in the late 70s . I have seen them on Craigslist for about the 400 dollar range. If you by used make sure everything works . Older equipment can be hard to find parts for

 

[General Zod]

Older equipment can be hard to find parts for

Yes, when an older welder breaks down, much time is wasted trying to fix it, and it becomes the project instead of the project that was to be done.

 

[Ulma Doctor]

here may be an answer to having both AC and DC capabilities

the conversion was less than $50

 

[FlyFishn]

here may be an answer to having both AC and DC capabilities

the conversion was less than $50

Thanks for posting that. I am familiar with rectifying AC to get DC. That was one of my questions in my first post - the stick machines that have DC capability - do they simply use rectifiers like that or is there any filtering to smooth out the DC?

If you take an AC signal and run it through a rectifier you will not have clean DC on the output. The power out of the rectifier will pulse at 30hz with a 60hz AC input - the opposite cycle of the voltage will be reversed and stacked with the initial cycle. So your 60hz signal is still there, twice, on top of each other = 30hz pulsed DC. It is DC because the voltage is all either above or below 0. It does not cycle polarities - that is what the rectifier is to correct.

Back in the day, inductors were used to act as some filtering to smooth out the ripple in the rectified DC post-transformers. It would seem to me, in today's day, and even back to the 80's or so, that capacitors would be a better solution to filtering the rectified DC to smooth it out. That is not overly complicated - you just add a capacitor, or series of capacitors, of appropriate values across the positive and negative leads of the rectifier.

What I don't know is if that filtering would make a significant difference in weld quality. The inner-electronics-geek in me says the DC must be filtered. But I don't know how you would go about capacitance values that would keep the voltage stable under arc. Mind you, pulsed DC (purely rectified) is NOT clean/stable DC.

I'll dig a bit and see if I can find some schematics for some of the AC/DC stick machines and see what they show. If a DC version of the tombstone welder is just a rectifier and a switch (no filtering) then I might as well just buy an AC machine and do the mod. We'll see.

 

[FlyFishn]

Here is an interesting page I just came across. This guy did a nice job with a DC modification on a Lincoln AC-225. He notes that the rectified DC was not good for aluminum and posted some waveforms. That is what I suspected... dirty DC. Good page, good info, though.

Lincoln Electric AC-225 (AC225) AC/DC stick/TIG welder conversion

 

[ericc]

If you look in the older manuals, you will there is a choke in the primary circuit. This can be made very simply with an old microwave oven transformer (rewound). It will make the arc more stable.

 

[General Zod]

At this point you're not looking for a welder, you're looking for a project to work on, lol

 

[markba633csi]

They usually use a large high current iron core choke rather than a capacitor. I believe the choke value is something like 1.5 millihenry
I think you would need a core about 3 times the size of a microwave oven transformer, it's a big fella
The core also has a special non-saturating tapered gap. I read about that somewhere- a Lincoln patent I think it was
-Mark

 

[FlyFishn]

I have a large choke from an old rack-mount Motorola repeater power supply from the 70's or 80's. I have no use for it... Maybe that would be a good donor. It weighs about 5-6 pounds if I recall correctly.

 

[NCjeeper]

For your price range you can get an Everlast 200 amp unit.
https://www.ebay.com/itm/POWERARC-200ST-SMAW-GTAW-Stick-200amp-DC-TIG-welder-by-Everlast-NOVA/202859497534?epid=2256316213&hash=item2f3b5e483e:g:WLMAAOSw64ha50h0