[ARC Tech-109]

Good luck on the saticon tubes, I have not seen any replacements for the better part of 30 years and whatever is out there is questionable at best. Sorry to be the rainmaker but with over 30 years of experience I'm only saying it like it is. Once CCDs and the ENG package took over the M3 series quickly fell out of favor. Despite being almost blind it's a wonderful camera for those who have the lighting budget, they have a wonderful color accuracy and picture "look" that says I'm a real professional without getting edgy with the contours.
I have not used my M3 for anything serious in 25+ years and it's since become a corner piece collecting cat hair.
Before taking the shotgun approach I'd strongly suggest finding a service manual for the M3 series and familiarize yourself with the details especially with the front end amplifiers hiding in the tube ends.