Alas many late model Tape Recorders are computer driven...
That's fine when they were new, but now they are 20 to 30 years old!

That means those computers inside them are Really Really Old now !

Some of the parts in the old computer designs are no longer available,
some are difficult to find, and some of the software (usally EPROMs)
have not been documented or backed up.

There ARE benefits to a good computer based design...
Superior transport functions and control.
Storable Transport and Audio alignments.
Self-Aligning Audio systems.

BUT When a fault happens somewhere in the Computer system in these old machines,
it is often difficult or impossible to trace down the problem IC,
meaning it becomes a crap-shoot.... replace a suspect IC, see if that fixes things,
replace another, then another and so on, until the fault is repaired.
That is time-consuming and costly !

 
Some machines like the Studer A-820 and A-827 actually have more than One Computer
in the machine - and ALL those various Computers must 'talk' to one another -
so the entire system must be running PERFECTLY or you get problems.
That means Communication timeing is critical between Computers, and often
that means 5 or more Cards have to be all perfect... no intermittent connections,
no minor faults in any of the various cards, all Sensors working perfectly.

The NON-Computer tape recorders are pretty easy to fix up - there's nothing
difficult in most designs, and documentation is pretty much available and
usually complete.
 
Here is a list of the Computer based Tape Recorders I have worked on...
 

Ampex:
the ATR-116 and 124
 
  Studer:
A-807     A-810     A-812     A-816
A-820 (all versions)     A-827
 
  MCI - Sony:
APR 5000 series     APR-24
 
  Otari:
Note: Many 5050's have a computer in their Counter design...
and most use a 4 bit Microcomputer IC for Transport Control (Otari I-0012)

MTR-10 and 12     MTR-15     MTR-20
MX-50     MX-55
MX-70     MX-80     MTR-90 (all versions)
MTR-100 (all versions)
 
  Revox:
C-270