40 minutes later, the speakers were back in play!
WOW! What I was missing! The temporary stand-in system was a Revox Piccolo II sub-sat system that was handy, filling the gap but no more. Decent, but not hardly maggies. I repacked the core for shipment back to Magnepan – that goes out today. Total cost for a new ribbon: just under $150 including shipping both ways. So, after discussions with the tech person at Magnepan, I reduced the fuse value from 3A to 2A for the tweeters, keeping the bass fuses at 2A. They are researching whether I should install the 1-ohm resistor as my speakers have the external crossovers with the correct matching serial numbers – but those numbers are below the series number that should have had the resistor. Meanwhile I am keeping the volume down. Fuses are cheap. Resistors are cheap. Ribbons are not.
For the record, their service, response, advice and general helpfulness was first-class. It is good to see an old-line audio manufacturer still holding its original values, still making a first-class product in its original location and still standing behind what they make and made in the past.
And like you said its good to find "service" really being SERVICE.