Lincoln Idealarc help needed(long post)

Must be too early in the morning. It's an LN-8, not an LN-7 and the Lincoln schematic shows the pot to be 10k. Maybe this unit didn't originally come with the welder........ Perhaps changing both pots to

-Jim

There are two (maybe more?) different tapers to pots. Linear and audio. Which one are you using? I don't know if this will work here or not, but it makes a big difference in volume. The linear is a straight 1:1 ratio and the audio is exponential. I think this is right, it might be something to consider.

Eide

Jim, I agree with Eide, it sounds like you are using pots that have a logarithmic taper that are intended for audio applications. Try replacing it with a linear pot. Possibly Radio Shack # 271-1715 for 10k,

For some reason I missed the original post so I copied it from someone's reply.

I don't agree with the other suggestions that it's a problem with the type of pot you're using. That could certainly cause problems but not the type of problem you described.

Based on your description you do get zero ohms at the control when at one extreme of the pot and if I remember correclty zero ohms should give you the maximum value that you have set on the local pot no matter whether your pot is linear or an audio taper. Zero ohms is zero ohms no matter how you got there. That means that if you press the pedal down all the way you should get whatever you have dialed in on the local control.

It sounds to me like your local pot is dirty/noisy although I'm not sure that would cause the kind of problem you're having. I'd check it with an analog multimeter so you can see how dirty it is. You can't check it with a digital because they update too slow but with analog the needle will jump all over the scale as you turn the knob if it's dirty. Dirt can cause it to open up intermittently and looking at the schematic I see that the remote pot goes through the local one so if the local one did open up you'd get minimum current.

From what you said about the measurements you get at the connector to the control board it doesn't really sound like this is the problem but it's worth checking.

Another thing I'd try is pressing the pedal all the way down and then adjusting the local control on the welder to see if it has any effect on the output current. And in case I'm backward on whether max ohms is minimum output and zero ohms is max I'd try it with the pedal pressed only far enough to get the switch to come on but I'm guessing you've already verified this.

BTW, I used to have an Idealarc TIG 250/250 which has an almost identical remote control circuit and I used a pedal with a 10K pot without any problems. It did call for a 5K but I got a great deal on the pedal with the

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"I'm not grown up enough to be so old!"

You're correct that the Idealarc TIG 300/300 is AC/DC CC machine but according to the manual on the LN-8 wirefeeder it can be used with a CC power supply. I didn't take the time to read the entire manual but section K3.1.3 is titled "Welding With Constant Current Welding Sources" and tells what to set the controls to for use in CC mode.

"I'm not grown up enough to be so old!"

If you take the time to read the manual, you will find that you can only run SUBMERGED ARC WIRE with the LN* with Constant Current machine. It states in the manual that (In the early years I worked SUB ARC ran on constant current machines Big wires and AC transformers when arc blow on DC was a problem}constant current is only used for subarc welding. YOU MUST HAVE A CONSTANT VOLTAGE MACHINE TO RUN INNERSHIELD AND OTHER OPEN ARC PROCESSES[such as MIG] This take me back to my original post that with TM

Alphonse, I think you're on to something. A little more digging in the LN-8 manual shows there is an optional variable voltage board that plugs in. It sounds like that's what's required to make the 300/300 work with the LN-8. My limited search so far, tho, has not turned up a Lincoln part number. Thanks for your help. I'll have to limit my welding to stick and tig for the duration and continue to use the Millermatic 35S for mig work. Thanks again.

-Jim

OK, I missed that part.

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"I'm not grown up enough to be so old!"

If I located one of these variable voltage boards from Lincoln, would that maybe solve my problem? It'd be nice to have a welder that can essentially "do it all".

-Jim

that maybe solve my problem? It'd be nice to have a welder that can essentially "do it all". If I located one of these variable voltage boards from Lincoln, would