Lincoln Precision 185 problem

Hello I have been using a Lincoln Precision 185 TIG /Stick welder , the unit seems to work fairly good except for the Amperage Control , as one goes Up
or Down with the Control Dial the digital Amp. readout bounces all over the place ,once I settle on the correct Amperage , the thing stays pretty stable , I haven't had the welder apart yet but am suspicious of the counting or pulsing mechanism that is hooked to the Amp. dial , from my HAM radio experience they usually use a Opto Interrupter or Hall effect counter , could also be using a mechanical contactor , wonder if anybody has had this phenomena and if so what did you find was the problem ? , I don't have a Service Manual , only the owners manual . Thanks' Phil L.
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Phil wrote:

Hi Phil, I have not been inside the Lincoln, but all the other modern welders that I have seen use an ordinary pot for the amperage control. Typically the front panel control is in series with the foot control which has another pot in it.
If the amperage reading wanders around when the arc is lit, it is probably because the current really is wandering around. You don't say what weld process you are using, but arc length variations will cause current variations. Stick and TIG welders are called constant current welders, but they are not all that constant. If you look in your manual at the voltage vs current curves for your machine, they are not flat as they would be with a real constant current power supply.
If you are refering to the setup current readout with no arc lit, you probably have a dirty pot on the front panel. Some pot cleaner (nobody has a mechanical tuner to be cleaned anymore) should fix that.
73 Bob
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OK Bob , yes it is only during the initial setup that I have the problem , once it is set at say 25 amps. it will stay there all day and not wander and I am using it for TIG , I will probably take it apart this week and try to solve the problem , I forgot that it could be a multi-turn pot , requires several revolutions to set amps, Thanks Again.

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For what it is worth, I have the same welder and see the same problems with the control. Maybe its just bad design.
The way it acts, I agree the control seems to be some kind of pulsed device with bad debounce, or something like that. It definately doesn't act like the control could be a pot as it sometimes makes big jumps and then starts moving from there. I don't think it has any endpoints either.
I've always been able to get it adjusted where I want in a couple trys, so haven't bothered to investigate. I did see one case where it seemed to jump from 105 Amps down to about 30 all by itself between welds. Couldn't figure out why I couldn't make an arc and weld all of a sudden until I turned around and looked at the welder panel.
I'd be interested to know if you learn anything about what is happening in yours.
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