I'm not aware of anyone supplying a new PCB for the Wolf, but it is probably a clone of another make, for which spares may be available.anyone have a link to a new circuit board
Alternatively, Tec-Arc ( a very well-respected manufacturer of pro MIG welders ) offer a repair service:
https://www.ebay.co.uk/itm/CLARKE-M...545435?hash=item1a7b0c2ddb:g:gncAAOSwQTVWCbnl
That is for a Clarke welder, they should be able to handle a Wolf MIG too, you could contact them.
Another option, since only the variable speed motor control part of your PCB is faulty, is to replace that function with a generic motor speed controller, such as:
https://www.ebay.co.uk/itm/12V-40V1...Controller-Volt-Regulator-Dimmer/392937746519