Thay only had 10k ohm and 5k ohm potentiometers when I went, and used the 10. I will gladly take a pic of the inside of the machine for you , junk, after all I've been called the "king of pics" in the past haha.

Update:
The surpluscenter.com 12V contactor has been working great. The contacts show no wear and the heat load seems fine. I will try to post a few pics of the contactor and wiring by the end of the week.

Firstfirebird,
If you get a chance for some pics, try to take one of the following:
1) pic of wires attaching to alum. plates and where they connect to.
2) pic of wires going from alum. plates to printed circuit board & wire feed motor
3) pic of where the ground clamp wire goes to
4) pic of where the wire feed small wire from the gun goes to (probably the PCB)

The 12V contactor link
(http://www.surpluscenter.com/item.as...-1722&catname=)

Sorry, until I saw your reply, I almost forgot.

The HF welder bit the dust, finally. It served me for 5yrs, making three complete turbo kits (one running 13flat in a V6 Corsica), repaing a lawnmower deck with strips of mild steel from Home Depot, making a new SS grate for my BBQ, multiple minor repairs, making a seat for my childrens' go-ped, putting a new exhaust on my truck, all-in-all I would say many spools of wire went through this $129 machine, and was worth every penny.

The problems started with a burnt trace on the board, and the fuse blew at the same time. I jumped the trace with wire, tested, and another trace burned. I followed both traces to a rectifier. Went to Radio Shack and replaced the rectifier with the correct replacement, and now the trace leading from the fuse burned (along with another fuse).

At this point, I gave up on it. We had a Craftsman gassed MIG sitting at the back of our shop, so I decided to take a look at at. We couldn't locate the parts to make the repairs necessary to the Sears machine, so the HF machine was hacked, thread with a die and the Craftsman is now a HF-tipped welder I can't believe how much more wire speed control I now have (no movement to stupid-fast), and the arc is certainly more consistant. The Craftsman has a transformer and regulator - whereas the HF had only the small circuit board and transformer. The HF had a small 9-12v DC brushed motor for the wire speed (found in a slot-track car), and the Craftsman has a worm-gear driven wire speed, and the motor is closer to the size of a soda can.

Here's the pics I took thus far, more upon request (HF machine)...







The circuit board was driven directly off the leads to the coil/transformer. It probably could have been repaired using a 120v to 1amp adapter from the infamous Radio Shack, but I figured that the welder served it's purpose and now can't wait to get some argon in the Craftsman just the consistancy of the spark is nice, and can't wait to see what happens with gas. Also noticed the nice fan mounted in-house from Sears.

Interesting. That HF machine doesn't DC rectify the AC transformer output. In order to use the contactor mod. you need a DC output (alum. plates with 4 diodes).
Since the HF doesn't have a DC and uses AC instead, that is why it doesn't weld as constant as a true DC- flux core machine.

That sucks that the PCB broke. It is great that you used the good parts on the Sears machine. That Sears box will last just about forever. You might be able to turn the old HF transformer into a batter changer depending on the output voltage.

The HF box states that it's 60-80v output.

Is that a rectifier on the left side of the coil in the pic (small black round with 4 wires)?

Yeah, I'm curious to see about the gas on the Sears machine, the HF tip has smaller orifices and the ID of the tube is a little smaller. If worse comes to worse, I still have a flux core welder that throws no slag in comparison to the HF.

I'm interested in doing the contactor mod on the Sears machine if possible. I'll post some pics of that machine if needed.

That voltage is too high for making a battery charger. I would say make an AC arc welder out of it, but the 115V arc welders just don't put out enough juice to be usable.

Yes, that 4-pin device with "2W04" is a bridge rectifier. It is a 2 amp, 400 volt rectifier. It turns the AC from the transformer to varying DC. The other reistors and FET create a stable/constant DC voltage for the wire feed motor.

There is more slag with the HF unit because it is AC and does only DC- half the time. The other half the time is DC+ which is not ideal for flux-core wire.

I am surprised the HF unit has a diffuser that you can use with gas. The Campbell Hausfeld unit I have uses Tweco components. Your HF is probably the same.

That Sears machine probably already has a contactor in it. Did you test it to see if the wire is always live?

I'm fimiliar with the rectifier you mentioned, that's the one I replaced thinking that was the problem in the PCB.

This is what I was inquiring about...



I believe the HF has the difuser bacuse they use the same parts on the gas and flux machines they offer to keep things simple. My concern is that the HF gas machine has a small (aprox 1/4") tube to supply gas whereas the Sears is at least 3/8". The Sears has a nice tip lead with the ground wrapped solid around the wire feed and gas hose (similar to a coaxial cable, not parallel like the HF). The HF tip has a lot smaller ID, and I was able to die the outside of the HF tip to thread inside the Sears tube.

Yes, the wire is always live. It gets annoying when doing multiple welds, or in precarious positions, it's easy to accidently touch the subject with the wire. How else would I notice the difference in the quality of the spark Actually, don't know if I ever mentioned that the Sears machine was not operable when I got it.

That 4 terminal device on the main transformer is a thermal switch. When the transformer gets too hot the switch will open and turn off the welder. I picked up a new Clarke 130EN that was non-operational for cheap. It turns out that one connection to the main transformer thermal switch was bad so the machine would not turn on.


I was guessing that the Sears box had a contactor in it, but it doesn't from what you wrote. Does it have two big aluminum plates that the wires from the main transformer connect to? I am guessing it does because you said it welds much smoother with less spatter.

EDIT: I welded in some O2 sensor bungs on the latest project this weekend...........upside down under a truck. The switched on/off wire voltage made all the difference in the world. I don't think I would have been able to cleanly weld the O2 bungs without the contactor in the machine because the wire would burn off when the wire contacted the steel before.

The HF machine in the picture doesn't have a main transformer DC rectifier for welding. You are actually welding using AC with that machine. Since flux-core wire prefers DCEN (DC-) that is why it spatters. The DC+ portion of the AC wave will make it spatter more.

The fix for it would be to buy a couple scrap pieces of aluminum and 4 diodes (Ebay) for about $10 - $30.

Thanks junk and Mark for the kind words back then. Finally got a TIG a couple years ago, and tried this yesterday. This was the 3rd attempt, think they will look better with more practise.