Nakamich Service Info

I would agree with ALL of the above posts.
It really has to be Willie Herman.
I have owned a Hermanised 582 and now a ZX7.
However you get what you pay for and expect a bit of a wait, his reputation is earned .
Depending what it needs you are likely to be looking at $500 to $800 plus BUT that should last you a lifetime.
I have a reference Hot Tuna Acoustic Live tape recorded on TDK SA on my zx7 that is simply out of this world and should convince any naysayers on the potential of cassette tape SQ.
Good luck and welcome to the wacky world of Nak decks but you probably have the best consumer deck in your hands right now.

Soundsmith is another excellent source for Nakamichi service. As with Willie Herman, you get what you pay for and you’ll need to be patient.

I did not have a good experience with NJ Factory Service.

Thanks so much. Do you know if they they do any mods or upgrades?

How deep is your pocket?
Lol.
Besides the normal run of the mill cap upgrades there is not much more  a good zx7 needs Tbh.

However check out their website for options and contact info.

https://www.willyhermannservices.com/

ESL labs in CT if you can wait and have the funds.