Opinion on Nakamichi azimuth tape decks please

I am thinking of buying a Nakamichi tape deck with the azimuth head adjustment. It will be used mostly for playing of old tapes (that's why I need azimuth). Nak made few of those: 670ZX, 680, 680ZX, 681ZX, 682ZX, Cassette Deck 1, CR-7A, DR-1, ZX-7, ZX-9 and the Dragon. I would not like to spend a lot of money so the Dragon, CR-7A, and ZX-7/9 are excluded. Any opinion on the others? I assume all of them have excellent sound quality; is it true?

I have read that the 680 models have very reliable transport mechanism and other components, but they were made almost 30 years ago. Anyone have recent experience with them? The Cassette Deck 1 was made in 1990-92 (don’t know about DR-1); how reliable are they? Do all of the old Naks require frequent calibration and servicing, and how expensive is it?

Any opinions will be greatly appreciated.
There were 4 Nakamichi decks with playback azimuth adjustments; the Dragon which is automatic and the CR-7A, Cassette Deck One and DR-1 (I believe) that were manual. The 670ZX, 680ZX, 681ZX, 682ZX, 700ZXE, 700ZXL and 1000ZXL had auto azimuth alignment for recording only, not for playback. I believe that the 680, ZX-7 and ZX-9 had manual azimuth alignment for recording only. You can generally find Cassette Deck Ones on epay for reasonable prices (if they work)and they are nice decks, Ihave one in my secondary system
Dragons can be found pretty cheaply these days, but the electronics (as you suspected) can be a bit wonky. I have a Nak 680zx which does have azimuth adjustment, but it's set based on recording a tone on one head & checking with the read head, so it's a setup step before recording. I didn't know the Dragon has auto azimuth on playback.

On my Nak, the mechanicals are still great, but the Dolby C mis-tracks. Most of my tapes were recorded in the 70's & 80's and by now are suffering major loss of high frequencies, and print-through distortions from storage, where the inner layers of tape transfer some of their magnetic charges to the adjacent layers.

I was recording LPs to CD-R last night and thinking how much better this process is than what I used to be able to achieve with tape. So much can be done in the digital domain with phase-free filtering and click/pop removal, not to mention much quieter backgrounds and no tape hiss. You can certainly listen through that, but it's nice not to have to anymore.

By the way, if you want my Nak 680zx to play with, it's in a closet & I'll give/sell it to you for postage/packing cost at the UPS store. Be nice to see someone getting some use out of it!
My memory matches Ktrogers'.

The Dragon was unique in that one channel(left if I remember correctly) of the playback head fit two pole piece sub assemblies with independent coils and gaps into the space normally occupied by one pole piece. Since both sub assemblies read the same track on the cassette, it followed that the head azimuth was correct when the output of both sub assemblies was in phase. A tilted head would cause one sub assembly to read the track a few milliseconds ahead of the other, resulting in phase difference.

The Dragon used a phase detector and servo system to continuously adjust playback head azimuth to maintain zero phase error and thus near perfect azimuth alignment.

This also means that you get great results from Dolby B and C noise reduction, since they magnify treble loss resulting from azimuth misalignment. Also tape playback quality is the same in both tape directions - this is usually a problem for auto reversing decks.

The record azimuth alignment featured on other Nak decks simply allowed one to adjust record head azimuth to match the playback head azimuth. It assumed that the playback head azimuth was correct, and provided no help for tapes recorded on other machines.
Excellent info above! On a budget, Naks may not be the best choice. They are antiques. There are only a few shops that can work on them (ESS is probably the best), and you might be shocked what it can cost to repair a Nak, especially a Dragon (over $2000 for a full rebuild). Even if you find one in really good shape, you will still need to spend at least several hundred dollars to get it calibrated, and belts, idler wheel, and perhaps capacitors replaced. They all need work, after all this time.
Do you know how I could get a hold of ESS? Tried to google it with no luck.