If the conv issue shows in the middle it needs adjusting. Best to
find a SAMS original PAPER manual. Before touching the magnets
mark them before moving. There may also be a locking ring.
Turn color off, run the contrast & black level down. Adj focus, turn off auto color switch. Converge......
Never seen a size problem on one. There is one adj that may be it BUT need a manual for that.
73 Zeno
LFOD !