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HF 125 flux welder

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mickri

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#1
Back in May I picked up one of these little welders while it was on sale for $90. Read all of the reviews and the modifications that you need to do to make it into a half way decent hobby welder. I have bought the rectifier, capacitor and the resister but have not installed them yet.
Finally got around to doing some practice welds with my 125 as it came from HF. After reading all the reports of bad welds and lots of splatter with a stock HF welder using HF flux core wire I was expecting the worst. I was pleasantly surprised with the results. No splatter to speak of. The welds look ok for someone who hasn't welded in decades. On minimum power I was able to lay some beads on some old rusty exhaust pipe without blowing through. On max power I did blow through the exhaust pipe but was fine on some 1/8" steel All in all I think that this welder will do just fine for me. I'll do some more practice beads before I install the rectifier and the capacitor.
 

Janderso

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#2
$90!, that's incredible.
I am looking for a MIG welder to add to my TIG.
MIG welding is just so darn versatile. I have heard less than positive things about the Flux wire myself.
Good for you!! Maybe I'll look into the Vulcan if I can't find a decent Craigslist find.
 

mickri

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#3
I looked for a long time on CL for a welder and everything seemed way overpriced. I ran across sellers of these HF welders asking almost new retail prices and wouldn't budge off their asking price. So when I saw that they went on sale I bought a new one.
 

homebrewed

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#4
I bought one of those cheap 90 amp AC welders (on sale as well) and immediately modified it to run DCEN. The mod looks a little funky because I attached the rectifier to a heat sink that's bolted to the outside of the welder. The most challenging part of the job was getting the very stiff wires dressed properly so I didn't put too much stress on the rectifier and capacitor terminals. Oh yeah, and reconnecting all the connectors to the controller board. I thought I had bricked the welder but discovered an unconnected wire harness. Once it was back in place I was good to go.

The heat sink may actually be overkill. I ran some test beads and did not notice much of a temperature rise on the heat sink. It would definitely look neater without it, but I cut a hole in the case under the heat sink so I could run wires to/from the rectifier. Now the heat sink covers the hole so I guess it stays.

BTW I found that most high current rectifier bridges are meant for 3-phase power. You can just leave one of the phases floating, or parallel it with one of the ones you are using. I used a single 60 volt, 60,000 microfarad capacitor and that seems to be OK so far. Some folks have claimed it's best to put several caps in parallel to reduce the ripple current flowing in each capacitor, but that makes the wiring job more difficult, and also makes it harder to fit everything inside the welder. I thought about putting the caps (or rectifier) in the top where the wire feed mechanism is, but found sufficient room in the bottom compartment.
 

mickri

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#5
I bought a 3 phase rectifier with a heat sink. I am going to connect the two wires from the transformer to the outside tabs on the rectifier and cover the center tab with electrical tape. I got a 60 volt 60000 capacitor and a 10 watt 260 ohm resister to bleed off the capacitor. It is a tight fit but everything fits inside the case. I am making solid copper connectors out of flattened copper pipe to connect the rectifier to the capacitor. The rectifier will be screwed to the floor of the case just in front of the transformer and the capacitor mounts to the front of the case. I will post a picture when I get it done.
 
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