Lincoln Idealarc 250 Tombstone doesn't weld...

admin

Hi everyone:I've had this Idealarc for at least 15 years. It has a Craftsman Hi Freq box on top of it that I use for TIG. You clip the stinger to a terminal on the Hi Freq box and flip it on, you've got TIG. I've also stick welded with it many times.It has been in my new shop now for about six years, and gets used every month at least a little bit.The other day I wanted to do some 7018's, and it won't strike an arc. I checked for voltage at the cable terminals, and don't see any. The fan runs when you turn the welder on. Just for grins, I turned on the Hi Freq box yesterday and the thing will strike an arc for TIG, but will not do anything for stick.What should I look for?Thank you.
Reply:Open the machine up and trace the schematic. If the fan runs your transformer should be good. The fan power is off a secondary. The weld power is also off a secondary. Check the poles/terminals of the polarity switch. 2 will ultimately come out of a secondary (one leg of the pair will come thru the reactor - what varies the weld current). The other 4 will be down-stream of the rectifier brick. If you have AC power at the polarity switch, but no power at the terminals - the switch contacts are your problem. If the rectifier brick bit the dust I suspect you would have an abnormally buzzing/vibrating machine, which you did not mention. If it was doing that you would surely have mentioned it. Either way, check the input and output of the rectifier (input would be AC and output you can check at the polarity switch).


Reply:For what it is worth, the open circuit voltage should be ~70 volts. Mine on 245v AC input is about 74 volts (a tad higher line voltage = tad higher OCV). If you have a different OCV on the AC side (no rectifier - straight out of the transformer + reactor) then you may have a problem with the secondary. I find that highly unlikely with as robust as these welders are so your first place to look should be the polarity switch and to ensure that the AC poles/terminals (straight from the transformer + reactor) have your OCV.
Reply:I would look at contactsA bug will die under the contract and make a great insulated varnish.This where the term get the bugs.Dave

Originally Posted by GregC

Hi everyone:I've had this Idealarc for at least 15 years. It has a Craftsman Hi Freq box on top of it that I use for TIG. You clip the stinger to a terminal on the Hi Freq box and flip it on, you've got TIG. I've also stick welded with it many times.It has been in my new shop now for about six years, and gets used every month at least a little bit.The other day I wanted to do some 7018's, and it won't strike an arc. I checked for voltage at the cable terminals, and don't see any. The fan runs when you turn the welder on. Just for grins, I turned on the Hi Freq box yesterday and the thing will strike an arc for TIG, but will not do anything for stick.What should I look for?Thank you.
Reply:

Originally Posted by GregC

I've had this Idealarc for at least 15 years.
Reply:Thanks everyone, for the replies. I mentioned in the title "Tombstone" so it is a round top. Probably from the 60's.No, it doesn't make any buzzing sounds, just the sound of the fan.I will pull covers and check voltages. Maybe it's just as simple as the polarity switch contacts.Seems odd that it will strike an arc using the TIG box, but won't using stick.I will report back.Thanks again.
Reply:

Originally Posted by GregC

Thanks everyone, for the replies. I mentioned in the title "Tombstone" so it is a round top. Probably from the 60's.
Reply:The HF box makes its own power for the spark. should be power off a 115 volt supply. Looking at the diagram that was supplied if you machine is like that one the cooling fan is on the secondary of the weld transformer so if you do not have weld output the polarity switch is burnt. also do not try to measure the voltage coming out of the HF box. IT will KILL your meter unless you have a meter set up that can read up to 8000 volts. the best most meters can measure is 600 to 1000 volts. You can see if the HF box is powered from a wall plug or wired into the welder some where and measure the supply voltage.
Reply:Okay. I finally had time to pull the round top cover off and check voltages. I have zero to .7 volts AC to the rectifier pack and the AC section of the polarity switch. Obviously, I have no DC voltage.It's interesting to note that the Hi Freq box is 115v powered. That would explain why it still works.  I just read the comment from Flyfishn about getting a voltage reading at the Hi Freq's power input. I have not done that. The Hi Freq box was mounted to the cover, and I had to take it's cover off, cut the AC line going out of it to remove it because some genius had run the wire through the lifting eye and I couldn't get the welder cover off with the wire through there. The Hi Freq has a twist lock plug that supplies power to its off-on switch, and then another two conductor cable from the off-on switch down into the welder's cover on the left side. I have not yet removed that cover to see where that goes. So, no AC to the rectifier pack. What could this be? Also, I was using my multimeter with an alligator clip grounded to the chassis for my negative lead so I didn't have to have both hands in there.  Is that problematic? I also put the negative lead on the body of a big capacitor in there, but no change on the readings at the polarity switch or rectifier pack.
Reply:Further progress this morning. I took the remaining cover off the left side of the welder. There is a big contactor in there. The fan is wired on the top side of the contactor, so it gets 115v as soon as the power switch is flipped up. I know you can hear the contactor whenever you press the button on the tig torch. I have 115V on both sides of the power switch, off and on.I pressed the tig torch button, and when the contactor closes, I have 66 volts on the positive electrode terminal. So obviously, the welder is not getting power until the contactor closes. But it used to work before without the contactor closing, because you don't hear the contactor unless you press the tig button. So I don't know what's happened here, and the contactor is not part of the original welder schematic.I can't see under the contactor well, but it appears the transformer primary is wired to it somehow. I may have to take the contactor loose to get a good look at it. There is a mess of wires underneath it. The one 2 conductor cord that I had to cut out of the Hi Freq box to get the cover off went inside the welder under the contactor. When I traced it out, the two conductors were wire nutted together, so that wire is not even necessary. It just interrupted the flow of 115V from power to the Hi Freq box power switch. Any suggestions?
Reply:Okay. It's fixed. I'm too embarrassed to say how, but it now welds. Thanks for the help.
Reply:Burn a pole in the plugin?250 amp Miller DialArc AC/DC StickF-225 amp Forney AC Stick230 amp Sears AC StickLincoln 180C MIGVictor Medalist 350 O/ACut 50 PlasmaLes
Reply:

Originally Posted by GregC

Okay. It's fixed. I'm too embarrassed to say how, but it now welds. Thanks for the help.