This seems to be an issue that is coming up recently, on units that fall in the age bracket as yours.
If I am remembering correctly the issue you're experiencing is more than like due a failure of component Q1 on the control board. Of course, my suggestion is to contact Hobart next week to verify that this is your problem.
If this turns out to be the issue, I wouldn't waste the money on a new board. This is a fairly cheap component to purchase, and not that difficult to replace either. Ok, admittedly I work industrial maintenance and have some experience replacing electronic components so I may be misjudging the ease of replacing this component, for someone who has no previous experience performing such operations.
MigMaster 250- Smooth arc with a good touch of softness to it. Good weld puddle wetout. Light spatter producer.
Ironman 230 - Soft arc with a touch of agressiveness to it. Very good weld puddle wet out. Light spatter producer.
MM 210-Looking for a new home locally
HH 125 EZ - impressive little fluxcore only unit