I can't speak directly to
the MTR-90s but do know that they are widely
regarded machines.
I just bought an MX70 1" 8-track from a guy that was also selling an MTR-90 MK III, to offset the cost of a Studer A827. That MTR-90 that he was
auctioning was in pristine shape .
I think that I've read that the MTR-90 has superior low-end response than
the later MTR-100s but it maybe the other way, around ..
I was seriously considering 2" 16, but for my purposes it was too heavy
of a machine to consider, and as a one man studio/one man band .I can
get by with 8 tracks .
But I digress ..
John Klett is a reknowned tech who is very knowledgeable about the Otari
recordes having serviced scores of them over the years. He's performing
some routine maintenance on my machine before it's shipped out .
contact him at :tech@technicalaudio.com and ask him what he thinks .
It may take a few days to get a reply(as it did me..) but he will take the
time to answer whatever questions that you may have, and thouroughly
That should give you the necessary info to make a decision.
Good luck !