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Sweet fixes on the cheap for my Mig. (Hobart 135)


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#1 FirefyterEmt OFFLINE  

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Posted January 10, 2011 - 06:43 PM

Well, a little while ago I knocked something off my work bench and dang if it did not fall right square on the wire feed to my mig. Well this last weekend I decided to open up the welder to see if maybe I could fix the switch. I found a very cheap potentiometer switch that could not be fixed. Now Hobart wants almost $50.00 for the switch, so a trip to Radio Shack (Where for once, the guy did NOT think a "potentiometer" was some sort of plant growing app for an i-phone) and I found a replacement 50 ohm switch for $2.99 and a set of knobs that will fit for $1.99 (The old switch knob would not work)

So using my AWESOMELY handy Harbor Freight alligator clip 12" test leads, I bench tested the new switch and it seems to work perfect. SCORE! Again, I have to mention just how useful these test leads are. I think they came in a pack of 10 or 12 with a few colors. Each end has an alligator clip with rubber boot on it. I have found these to come in so handy it's not even funny! I am going to temporally install the automotive ignition on my hydro-12 to see if the motor runs.

Anyway, back on topic... the new switch is 10x better that the cheap one Hobart had in there and for 10x less the cost! I have lucked out with this mig three times now. I got it for free not working. A little test meter digging later and I quickly found the on/off switch was bad. I stuck a switch from my tool box into it and 5 spools of wire later its still going strong. Next was the main circuit board failed, the on-board relays were junk. I found with a quick google search that I can buy the relays separately for $5.00 each. The board was $300..... The new relays were a pain, but it fixed it like new. Now the switch fix! Just awesome! What I should do is to buy a proper ground clamp.... but that standard spring clamp I stuck on the end just works perfect too. :rolling:

Edited by FirefyterEmt, January 10, 2011 - 08:32 PM.

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#2 olcowhand ONLINE  

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Posted January 10, 2011 - 07:42 PM

Look out.....now we all know who to call when we have mig problems! lol

#3 Bolens 1000 ONLINE  

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Posted January 10, 2011 - 07:49 PM

Look out.....now we all know who to call when we have mig problems! lol


:ditto: :thumbs:

#4 FirefyterEmt OFFLINE  

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Posted January 10, 2011 - 08:36 PM

Well, don't thank me quite yet. While it did raise and lower the feed speed, when I tried to weld with it, I noticed the scale was off and it runs too fast. On my high heat setting (4) I need to run the 10-100 scale for the wire feed between 15-20. It should be much higher than that. So, I am working out the possibility to install a resistor to drop the output down. I have not messed with them much so I need to research it a bit. I mean, I can use it and have a little adjustment, but it will not work well on low settings with the wire feed so fast.

#5 coldone OFFLINE  

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Posted January 10, 2011 - 08:52 PM

Ohm out the original pot to get the resistor value of the pot. There are 3 legs on it two legs will be the resistor and the third will be the sweep arm. Once you have the value you can then match the value to another pot, ie 10Kohms.
It could also be printed/stamped in the pot housing.
If there is a model number on it google the number.


1 and 2 are the resistor, the value will not change when truning the dial
3 is the sweep arm. It will vary when turning the dial. Usually turning the dial fully oneway will max out the sweep arm and give you the full resistor value.

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#6 MH81 ONLINE  

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Posted January 11, 2011 - 01:02 PM

:ditto: You may also see if you can figure out if it's linear (straightline) or logarithmic adjustment. One would assume it's a linear pot, but it may be a log. Did it say on the package of the RS unit what the taper was?

#7 olcowhand ONLINE  

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Posted January 11, 2011 - 01:21 PM

I have to say you guys have went beyond me. I don't know linear pot from the kind grown & smoked in the backwoods around here! :bigrofl:

#8 Texas Deere and Horse OFFLINE  

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Posted January 11, 2011 - 01:30 PM

I have to say you guys have went beyond me. I don't know linear pot from the kind grown & smoked in the backwoods around here! :bigrofl:


Thats too funny Daniel !!!!

#9 MH81 ONLINE  

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Posted January 11, 2011 - 08:26 PM

I have to say you guys have went beyond me. I don't know linear pot from the kind grown & smoked in the backwoods around here! :bigrofl:


I'm moving to Dan's Woods.:rofl2:



You might try this.
Posted Image

Or the article it's from, it explains more. http://sound.westhost.com/pots.htm

Edited by MH81, January 11, 2011 - 08:32 PM.


#10 mjodrey OFFLINE  

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Posted January 12, 2011 - 05:47 AM

Look out.....now we all know who to call when we have mig problems! lol


You got that right.:thumbs:

#11 FirefyterEmt OFFLINE  

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Posted January 12, 2011 - 09:16 PM

:ditto: You may also see if you can figure out if it's linear (straightline) or logarithmic adjustment. One would assume it's a linear pot, but it may be a log. Did it say on the package of the RS unit what the taper was?


From what I found on a Hobart welder site, it is a logarithmic adjustment pot... I can not ohm out the old one because of how it broke it is no longer a switch as to say. The RS one is liner too. Any other options, or do I really need to buy the Hobart one? From what I have been seeing, it looks like I might need an audio pot. The curve in the chart sure seems to show what I want the switch to do. (well, better than the liner anyway)

Edited by FirefyterEmt, January 12, 2011 - 09:45 PM.


#12 MH81 ONLINE  

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Posted January 12, 2011 - 09:44 PM

If you take an ohm meter & measure across pins 1 & 3... that should tell you the value.

If it's a log taper, here's a page with pots. You're looking for logarithmic or audio taper.

Search results for potentiometer




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