welder repair help.

Date 03-24-2009 23:00

we found an old hobart welder at the plant i work at. it was missing a 460 volt plug and needed some set screws to make the amp adjustment knob work. we got it all doctored up and welding. My question is that when welding it acts like it is in straight polarity when it is hooked up for reverse polarity, by the way it has no switch to change the polarity if you were going to ask. We blew out all the dust made sure all the internal connections wre tight all new cable, ground, and stinger. It does weld fine other than it kinda pulses like it is in the wrong polarity. It also throws the 6010 sparks if ya know what I mean. I think it is from too many years of gouging. any help would be appreciated I like to tinker and fix up the used and abused toys I find at work.

By aevald

Date 03-24-2009 23:24

Hello scrappywelds, as to the polarity question, if you have a DC volt meter that is digital, attach the positive test lead to the + terminal and the negative one to the - terminal. The reading that you get should be a number and nothing else if the polarity is correct, if it isn't, most digital meters will show a negative sign on the output numbers indicating that the polarity is backwards. If you are using an analog type meter the needle will bury to the left instead of sweeping to the right and indicating the relative voltage. If it does dive to the left be sure to disconnect from the terminals as quickly as possible.
Is this machine a motor/generator or is it a transformer/rectifier type machine? I'm guessing the latter and possibly you might consider removing the cover and taking a look at the internals and possibly checking the input connection wiring for loose or corroded connections and possibly checking the contact points for the main switch. In general just a good going over to see if you do have any corrosion issues with anything can certainly help. You might also include any machine model/serial #/or other information to decribe more closely what you have. Have fun and best regards, Allan

By scrappywelds (***)

Date 03-25-2009 00:56

I will check tomarrow for serial # / model. It is a transfomer/rectifer. we did check all the internals we could get to. no corrsion problems everything tight. Though the rheostat does have some copper oxidations issues. we tried a electical connact cleaner, but it really didn't help. also the little brush thing is a little worn looking. What is the white stick I have seen used to clean it called? I will get our electricen who is helping me take a look at the terminals with his meter. thanks alot

By Milton Gravitt (***)

Date 03-25-2009 00:46

This is just a shot but on some of the older welding machine you had to switch the welding cables around to switch polarity.
M.G.

By scrappywelds (***)

Date 03-25-2009 01:01

yeah of course it is right. they are marked factory + electrode - ground , but this welder from what I was told by some of the older plant employees it is atleast 20 years old and hasn't ran in 5 years. They used to do all repairs on tools in house' so someone could have fooled with it and messed it up. It does look at least factory.

By DaveBoyer (*****)

Date 03-25-2009 02:22

Get Your electrician to check the rectifiers and the primary amps on each leg. 20 years old isn't that old in an industrial Hobart, could be 50 years [or more] old.

By scrappywelds (***)

Date 03-25-2009 21:39

It is r-400 model. 16rt-3437 serial #. 230/460 volt power source. It welded a little better today. Let me ask this if it was hooked up (internally) to take a 230 volt power source and we pluged it into 460 volt could that cause the problems I am experiencing?

By aevald

Date 03-25-2009 22:52

Hello again scrappywelds, it would probably go BOOM, followed by clouds of smoke!........ that is if it was wired for 230 and you supplied it with 460 input power....... if the reverse was true I don't know that it would go boom but it would likely do some really strange things and make some strange sounds. Haven't ever done that so I don't know for sure and you shouldn't take my word for it. Best regards, Allan

By scrappywelds (***)

Date 03-26-2009 01:53

to be honest it was just a question. The only welding outlets are all 460 volt. there is very little in the plant that is 230 anyways. Like I said it is old used and abused, when it started messing up the plant guys cut the power cord and shoved it in a corner. There is about 5 welders in that corner we all ready fixed 2 of them allready, because we needed more welders for an outage.