What a brilliant deck AD-F810 is. I have owned 2 for over 15 yrs and they are superb both in quality, recording sound and longevity. The only issue I ever had was that belt eventually died on my first one, but once it was changed it worked as new, despite serious usage over the years. You can easily still buy a replacement belt on the internet should you need it.
I'm not too techy but I read on a forum that AD-F810 has one of the better transports, very good head - same, as in the Aiwa XK-007 Excelia and a good circuit.
What I do know for sure is that performance is outstanding! Quality of sound: crisp and a perfect replica. I would only ever consider changing these decks for a Nakamichi Dragon. No interest or need whatsoever for any other deck out there. 810 is a keeper.
I also own AD-F850, and there is a noticeable difference in recorded sound quality from AD-F810, so I cannot recommend AD-F850 to anyone. Nor ADF 410 and 450 which I also owned, but they are not 3 headed anyway.
I am wholeheartedly recommending it to you, especially if you are into Maxell and That's tapes which work like a dream with this deck.