Hi hogan!!!
I believe that both Al's are barking up the right tree - so to speak! ;)
Just to add to both Al's & Larry's suggestions which I would also follow the same initial course of action, I would also check to see if the wire feed motor has an encoder in it as most do... there should be a cover plate on one end of the motor that houses the encoder... If the technician did a thorough once over, and either found that the encoder or any of it's other components was not installed or working properly then there may have been a reason to open that end of the motor to have a look see and finally, there's always the slight possibility that when checking the encoder wheel, it might have been loosened from it's original position, or harmed inadvertently, or reseated in a different position by the tech when they closed the cover plate, and if the encoder is reseated, and not corresponding to the WFS pot position as to it's own starting point of resistance in relation to what was originally being fed back to the microprocessor board either in the wire feeder or to the power source itself, the possibility could occur, and thus be the root cause of the problem... Then again, this is pure speculation on my part!!! :) :) :) Btw, what brand are referring to here? Did you call the technician or who they represent to see if they could offer an explanation???
There are many possible scenarios that can be ultimately the root cause of the problem you're encountering so, I would cover all of the bases when troubleshooting this type of problem because, who knows!!! It may end up being something as simple as the tension adjustment on either the drive rolls, or even a misalignment of the rolls, or the spool tension needs adjustment, the possibility of an obstruction of some sort in the conduit which would not always directly affect the constant rate of wire feed... Instead, the constant feeding of wire is slower as a result and so on...
If you eliminate the simple but often overlooked possibilities, then you're left with the more complicated electro-mechanical, or electronic components at both the wire feeder and the power source. always refer first to the maintenance & troubleshooting guide in the operating manuals, then check to see if there are available schematics online @ the manufacturer's website if you're able to troubleshoot electro-mechanical & electronic components based on what the specs in the schematic & other given specs found in the operating manual dictate, and if you're still at a loss, then call the manufacturer's customer service line... That is, unless it's a problem that's still covered under the manufacturer's warranty because, you'll automatically void it if you try to troubleshoot, and attempt to make the repair only to find out later that you were unsuccessful in doing so. That's the best I can offer to you right now hogan. :) :) :)
Respectfully,
Henry