I repaired my Miller Synrowave 250 the second time it broke.
I have the early production one (old style board). The output
just goes ON at some fixed setting. Panel control or foot peddle
does nothing.
The schem. did come with it. Turns out they used a now obsolete
op-amp that was prone to fail. No pin for pin modern replacement.
I cross wired a new op-amp type in to check it out, and all was well.
Ebay turned up plenty of the old type. Swapped it out and.. Viola!
I put the thermal fan control mod in it while it was open.
RichD, Atlanta