Chicago Electric Dual Mig 151 T/2

While researching hobby welders that would not ruin me financially I came across this thread prizing this cheap Harbor Freight welder and their great potential to act as nice and pricey Lincolns, Millers or Hobarts. That could be accomplished by making a series of modifications to the circuitry, and any thing that includes word "MOD" receives my attention...
Link to original thread on a super nice and helpful forum:

Here is a wiring diagram provided by weldingweb user holabr, I found it absolutely necessary when you mess up wires...

The welder itself is Chicago Electric Dual Mig 151 T/2 made in Italy (old and rather rare model).
Parts required for this mod are:
565-3332-ND 100000 uF Capacitor
338-1366 3” Capacitor Bracket
GBJ604-FDI-ND Bridge Rectifier
493-1081-ND 100uF Cap (Motor)
KAL2550F-ND 50 Ohm 25W Resistor (Cap Bleed)
259-1433-ND 220/240VAC 120mm Fan
(Italicized part numbers are from Digi-Key Website)

Plus extra mounting hardware for your cap and fan.
It is worth noting that this cap dimensions are 3" wide and 5.625" tall while the welder compartment width is only 6". That poses bit of a risk if your terminals could potentially touch the chassis. It is also pretty crowded in there with all the wiring and components. For that reason I decided to mount it in the welding wire compartment, width of which is just over 3" - which is perfect.

The only two concerns with this arrangement that I found are: exposed cap terminals - these will need to be somehow covered up in case welding wire unwinds and touches both terminals, and ability of mounting a 12lb spool of welding wire. While initially I am not concerned about switching to large spool, I can see doing it in the future as it is definitely more cost efficient solution. This is what this modification looks like:

Click on the image to access original thread.
What you need to remember is that the height of the compartment is 12", 12lb wire spool diameter is 8", and that capacitor, again is 3". That leaves you only 1" to separate the components. Also, because of the cap I would have to mount the large spool slightly lower than the original mod suggests.
Now, back to the mod.

The large capacitor is mounted using optional bracket (at the base), and a strip of flashing (at the terminals). I can also see rubber grommets through which I will lead both wires from the terminals.

To mount the fan you just have to drill 4 holes through the back panel and re-solder wires from the original fan.

Small capacitor is soldered between wire feed motor terminals. If you have doubts which terminal is positive, which is negative, and which cap leg is which take a look at suppliers diagram for the cap, and trace the wires from the motor to PCB, in my case #7 was positive, # 10 was negative.

Next would be the bleed resistor. I tried soldering 10GA wire to it but it looked like crap, so instead I crimped two ring terminals bent upwards which nicely fit between rectifier plates.

The most difficult part of this mod turned out to be small rectifier but only because I clipped all of the wires at once and then I lost a track of them. But the wiring schematics came in handy again.

Now I just have to figure out what to do with small diode that came with my supplies. But the mod is pretty much done! I spent some time reshaping and re-routing the wires but that is mostly for aesthetic purposes, and maybe the air flow. Here it is - FINISHED PRODUCT.

And here is a picture of what it looked like before:

I decided to make two other modifications, one was an addition of gas line connector.
the other one was replacement of ground clamp and wire with a nicer one from a plasma/tig welder.

And there you have it. Overall I spent approximately $300 including welder and supplies, somewhat close to what I would have spent if I wanted to purchase small Miller or Hobart. But where is the fun in that?

Mar. 12, 2011 13:11