I think you're thinking about a Dolby B encoded tape being played with Dolby C decoding. That's an outright mess. But Dolby C encoded material is very much playable with Dolby B when there is no other option...and 'no dolby' isn't an option on Dolby C encoded stuff imo. But regardless, problem is solved.
Rudy, I should thank you. Better late than never, . Your tips prevented me from breaking the plastic frame and though I did loose the spring trying to put it back in, it flew away. Ended up finding it a couple of weeks later, randomly while doing some cleaning, I glanced over to the far corner of my desk and there it was. Anyways, don't think I ever thanked you after I posted that the 701c was fixed. Your post was the kind of post that brings me here to this forum. Cheers.