Lincoln TIG 300/300 help

Greetings, Does anyone out there have any servicing information for a 80's vintage Idealarc 300/300? I've put the unit on a load resistor and can only get it to deliver about 50A worth of current regardless of the heat selector. Doesn't matter if I use the front panel control or the Amptrol, AC or DC. I suspect the problem may lie in the output control pc board. The manual I have for it doesn't show the schematic for the board. I found a similar schematic for a TIG 250/250 on the Lincoln site, but it's not identical to the board that's in my welder. With that being said, are there any common failures for this machine that I should be looking for? I got a great deal on it($200), so I'm not afraid to stick a bit more $$ into it. It welds like crap right now. Thanks for any help/advice.
-Jim

Hi Jim, I have some information, and I'll be happy to check my files. What is the code number for your machine?
You could also contact Lincoln Customer Service at 800-833-9353. Those guys can be very helpful, even on some very old machines.
Cheers, Bob
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replying to Bob, bernie wrote: hello, I have a Lincoln Idealarc 300 serial447478 no output on pos terminal only 30v in stick mode on medium range same thing on Tig . I need someone to guide me thru the troubleshooting thanks if you can help snipped-for-privacy@orange.fr

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http://www.arcowelder.com /
call and ask for Dennis. Very very sharp guy.
Gunner
Rule #35 "That which does not kill you, has made a huge tactical error"

Bob, Here's the info from the nameplate: Model: TIG 300/300 Code: SPL-B513-84 Serial: AC591771
Thanks for any info and thanks to the rest of you for your help. I'll try Lincoln and Arco and see what happens.
-Jim

Jim,
The machine you have is special, that's what the "SPL" stands for in the code number. It's not a machine that would have been offered for sale to the general public. It was ordered by a specific customer with some feature they wanted. What makes it special could be as minor as a different paint color, or as major as a transformer designed to operate at an unusual voltage.
I have contacted one of my friends at Lincoln, he should be getting back to me to let me know what's special about it. I'll post here as soon as I know more.
Bob
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Jim...have you plugged in the foot pedal and mashed down on it to see if the amps increase? There is a possiblity that your machine was used in a welding cell or with other outboard controls, based on the gentlemans comment about it being a Special.
I have a big assed Hobart Cybertig 2 that will not put out dick without a dummy plug in the foot pedal socket, or the foot pedal itself, no matter if its set for tig or stick.
And I need the dummy plug...sigh
Gunner
Rule #35 "That which does not kill you, has made a huge tactical error"

Gunner: Yeah, mashing the pedal produces a change in welding current, just like the front panel control, but I can never get beyond 50A, regardless of pedal/knob position. Even setting the current control to it's highest setting(300A, which should probably trip my breaker), results in 50A at the output leads.
Bob: The welder was originally purchased by the Govt. so the SPL may relate to some additional badging that's attached to the welder. It's painted the same battleship grey as others of that vintage. The drawing number for the schematic glued to the inside matches the drawing number in my manual, so I would assume there were no circuit changes. Same with the part numbers on the control board and timer board.
I found an outfit that sells refurbished control boards for about $125, exchange and I wouldn't mind spending that to fix it. However, if that's not what's wrong, it's money wasted and the frustration level increases.

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Jim, I was told that the machine is the same as a code 8888. It was shipped in nonstandard packaging, and was prime painted only. You might want to write down that code number, it may come in handy if you ever need parts or specific information.
I used to work in the transformer welder department at Lincoln back in the mid 80s. They would move people around as demands changed, but I spent most of my time assembling on the TIG line. I may have had a hand in building your machine. : ) I also built lots and lots of AC-225 (tombstone) machines. If I recall correctly, machines that were "prime painted only" looked just like the standard gray that was used on the standard production machines.
I checked my files and found that I had several packets of troubleshooting information from past Lincoln service school classes, but none for this machine. One of my packets is for codes up to 8887. (Go figure!) I'll forword everything I have received so far about your machine, but you may have to call and speak to one of the TIG troubleshooters at Lincoln.
I would definately try my best to pinpoint the problem before sinking any serious money into the machine. I'm not an expert in repairing these particular machines, but the problem you described could possibly be a shorted saturable reactor coil. If this is the case, it may not be worth repairing. If the machine always acts like it's in the lowest range, no matter where the range switch is set, that would seem to me to be the most likely cause, but check with someone who really knows these machines before you take any action.
Good luck! Bob

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I wonder if the current control pot took a dump? Measure it with an ohm meter and see if you get a large change in resistance from one end of the movement to the other. If it goes to a certain point in the first part of its travel, and never goes higher as you increase the setting...its toast. I saw that with a foot pedal I was fixing for a client.
Gunner
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"At the core of liberalism is the spoiled child - miserable, as all spoiled children are, unsatisfied, demanding, ill-disciplined, despotic and useless. Liberalism is a philosphy of sniveling brats." -- P.J. O'Rourke

Jim, Any luck with the old TIG? I just had a thought. I have heard of machines that are setup in a particular application where the engineers want to limit the changes that can be made by the operator. One guy told me that several switches, in a machine he was working on, were disabled in an effort to prevent anyone from changing the settings too drastically. I know such a thing would be a long-shot, but you never know. It's probably worth taking a good look at your machine to see if there are any signs of internal connection modifications.
Bob
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Good note Bob
Another idea - in the pedal - is one end of the pot - there are three leads - one off ? Maybe the cable has a bad wire for one ?
A three terminal would be used for voltage - like a volume. A high voltage on one end, the other end is the low end (maybe gnd) and the center (wiper) sweeps from one to the other.
If the GND is broken somewhere, then a series resistance of some value is generated from the high level to the wiper. It would depend on the input (drawing) current as to the drop.
If the High side was broken - then it would be a resistor to the low setting. Might be this one! You might be just setting above the low side due to a voltage drop in the lead.
I bet you have a broken POT, Broken wire, or like Bob - an internal terminal un-plugged to prevent putting 300 amps on a little tiny thing.....
Good luck Gunner, Martin
Bob wrote:
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Hi Guys, No progress yet. I've had a bunch of projects dropped on me at work, so I've been unable to talk with Lincoln or Arco as of yet. I like Bob's idea of an internal modification and being as it was a Gov't spec'd unit, it's very possible although I've yet to discover any changes in the wiring. The foot pedal is good. I've checked the resistance readings from one end to the other, no issues. And even if it was bad, the front panel control should still be operational. I get the same results no matter which pot controls the heat. A colleague of mine has a friend that's closing down his shop and what's one of the things he's selling? Another Idealarc TIG 300/300..... I need to find out what he wants for it. This one is known good. I'll keep ya posted. Thanks again for all your assistance.
-Jim

replying to Bob, bernie wrote: hello, I have a Lincoln Idealarc 300 serial447478 no output on pos terminal only 30v in stick mode on medium range same thing on Tig . I need someone to guide me thru the troubleshooting thanks if you can help snipped-for-privacy@orange.fr