Old Hobart RC-256 problems

[crjohnso]

This is an older welder that was given to me (Hobart Model RC-256, Spec 5269D-1, Serial 79Ws13165). It fires up, but blows the main fuse when the trigger is pulled. Looks like there may be some bad parts in the 404209A board the control wires go to. Could this be the source of the problem? Is this board or the parts to rebuild it available? Any help is greatly appreciated.

Thanks,
Craig

[hankj]

Hi, Craig. Welcome.

You've come to the right place. A Hobart Expert will surely answer your post tomorrow around the start of business.

I hope you get a solution. that's one **** of a mchine!

Hank

[Hobart Expert Keith]

Craig,

If you are refering to the main fuse on the RC256 then yes the board could be the problem. The board is only a bridge rectifier, resistor and a couple of caps. All this is listed in the owners manual on the schematic. All of these should be available locally to rebuild the whole board. The only other item to look at would be the contactor coil. It is a DC coil(110VDC) and should measure @ 17 ohms. If it is shorted it could have failed the board.

Keith

[crjohnso]

Keith,

Yep, that is the fuse I am referring too. As you might imagine, I do not have an owner’s manual with this free welder, do you know where I might acquire one? Also, I’m not sure what the contactor coil looks like, or where it is located? Is it similar looking to an automotive coil? Again, I think the owner manual might work wonders here. “All of these should be available locally to rebuild the whole board”… locally from somewhere like Radio Shack, or? If I test the contactor coil and find it is shorted would it be available somewhere as well?

Thanks again,
Craig,

[Hobart Expert Keith]

Craig,

You can get a manual from our literature department at literature@millerwelds.com . Just give them the SPEC# of the unit and they should be able to help you. If the coil is bad you may be on the hunt. The components on the board shoul be readily available at Radio Shack.

Keith

[crjohnso]

Thanks Keith, I will look into the manual and do some testing. I will report back with any findings.

Craig

[crjohnso]

I got the schematic for this machine and am 90% sure I found the Contactor Coil (referenced earlier in this post). On the Schematic it calls it a "secondary contactor" and is the only part rated 110VDC. It has two wires on the side, and a contact point in the front. Question is how do I test to get 17ohms? I pulled it out to bench test it, but get nothing off of the two terminals and it jumps all over and eventually settles at .1ohm if I put both leads on the main contact point. Am I doing something wrong or is this part no good and therefore giving no reading? Or am I even testing the right part? What should my next step be?

Also, I have all the parts to rebuild the board (cheap), but don't want to fix it only to blow it out again due to a bad contactor coil, etc. As for the board, the resistor looks like it has battery acid on the bottom so am guessing it has leaked and is no good. I will rebuild the whole board to be safe as the parts are super cheap. Again, want to make sure there is nothing else wrong before I put a new (rebuilt) board in.

Hope that all makes sense... sorry for the long response!

THANKS AGAIN!
Craig

[Hobart Expert Keith]

Craig,

There should be two small terminals on the coild itself that the small control wires go. That is where you should read the 17 ohms. Make sure you disconnect the wires from the coil to get a good reading.

Keith

[Mike W]

You should see the wires going to the coil. They would be separate from the contacts. If you get a real low reading, you could make another test by hooking a 120 volt lamp in series with the coil. Power it up and if the lamp lights up bright, measure the voltage across the coil. If it is zero or a few volts, the coil has a short.

[crjohnso]

Let me try to rephrase a little clearer ;-)
In my last post I mentioned two wires (but probably should have said terminals) and a contact point (or surface) on the front (of the contactcoil).

I disconnected the wires from the Contact Coil, and tried to get a reading from the terminals on the side, but got nothing, not even a blip. I took the coil out of the machine to be sure it wasn't grounding, etc. and did a bench test and still nothing off of the two terminals. In the front of the coil there is a contact surface which does give some weird readings and seems to settle at .01ohms, but I don't think that test is really valid anyway. At this point can we assume the Contactor Coil is faulty and I need a new one? Should I bring it somewhere for a more thorough test? Where in the world would I get a new one... any suggestions?

And of course thanks again for taking the time to help me through this!

Regards,
Craig

Thanks,
Craig

[crjohnso]

Bumping this to the top to see if I can get any answers/suggestions to my last post in this thread... Hobart Expert Keith? Anybody? ;-)

Thanks,
C-

[hankj]

Craig,

What kind of meter do you have? If you measured the coil resistance and got no reading (open coil) that should be your answer. Did you try Mike's voltage drop method?

Hank

[Hobart Expert Keith]

Craig,

It does appear that your coil is open, but like Hankj you might want to try the voltage drop test just be sure you use DC bulb and voltage. If the coil is bad you may be hard pressed to find one.

Keith

[crjohnso]

Hard pressed to find one eh? No suggestions, no old parts bins lying around... not supported in any way I take it? Sure hope it isn't dead... will try the Volt test next.

Thanks again Keith!!!!!

C-

[Mike W]

Take at look at http://www.surplussales.com/. I am not familiar with that machine but you should be able to find a substitute contactor one way or another.

Here is the page for contactors: http://www.surplussales.com/Relays/REcontacts.html
There are some with 24-28 volt coils. You could use one with a resistor in series to operate on your 110 dc circuit. You just need to have the proper current rating for the contacts.