Sony Rather than break down the Sony RTR decks by model, it’s easier to break them down into single motor decks, and 3 motor decks, as the common failures differ significantly between these two types of decks.

Single Motor Decks and recorders. Sony made countless 7” consumer reel to reel machines, both in tape deck and built in amplifier models. I believe that Sony was the number one seller in the world of reel to reel decks, as it seems that everyone owned one at some point in time.

A typical Sony single motor deck, this one with speakers built into the lid (TC-200)

Single motor Sony decks were made from around 1956 to 1982, with the TC-399 being the last single motor deck that Sony made. The early models were tube, with Sony switching to solid state around 1968 or so. Whether tube or solid state, the single motor decks suffer from  several maladies that can render a deck to be a write-off:

Hardened white grease. Sony was liberal with these decks throughout the transport, to keep things moving slowly. Unfortunately, the grease hardens over time, especially if a deck has been stored for decades, causing all sorts of transport  and mechanical problems throughout. Removing the grease and relubricating the transport  is a very labor intensive job, usually requiring 2-4 hours to unseize parts and to get rid of the old grease.

Bad motor run capacitors, and bad motors. Many single motor decks use a ‘run capacitor’, just like modern day air conditioners do, to start the motor when first powered up. These motor caps fail often, and are mandatory to be changed in any single motor Sony deck. If a deck has been run too long with a bad motor run capacitor, the motors can overheat, and fail without warning. We’ve seen several motors fail a couple of hours after the motor run cap has been replaced. These motors are no longer available, and used eBay motors may be in as bad a shape as the one coming out of the deck.

Bad rubber idlers. Each Sony single motor deck used several rubber idler wheels in each transport to transfer the power from the motor to various parts of the transport. This rubber hardens over time, and cannot be reconditioned with fluids like ‘Rubber Renue’ that strips off the oxidized layer of rubber to expose fresh rubber underneath. While this treatment seems to work initially with Sony idler wheels, they will always harden again within 24 hours of applying the Rubber Renue, and the torque from the motor is no longer transferred to the transport. While Terry’s Rubber Rollers does put new rubber  onto these idlers with great results, in order to do the job right, all idler wheels need to be done, and the cost goes up well past the value of an entry level Sony deck.

Soft Heads- In their early decks, prior to the Ferrite heads coming out around 1973 in many Sony decks, it wasn’t unusual for an often-used Sony deck to go through 2-3 heads in its lifetime. I’ve seen many Sony decks come in with very worn heads, and it’s not worth relapping these older machines.
All of the above reasons is why I state in the tech summary section that most Sony single motor Sony decks simply aren’t worth repairing. Even decks with the ferrite heads will have numerous other problems that makes them not worth putting  money into. You’re better off buying a post-1975 Akai or Teac deck that will provide more value and longevity than trying to repair an old Sony deck.

3 Motor Sony decks  The 3 motor Sony decks that use direct drive reel motors, and (usually) a belt drive capstan shaft tend to fare far better  than the single motor transport decks. Again though, Sony has unique problems not found in other brands:

The high end Sony TC-765. An excellent performer once the bugs have been worked out of it.

Brakes- Sony used really poor brake bands that wear out quickly compared to other brands, and these need to be relined. If there’s any sign of tape spillage when FF or REW is used, both brake bands need to be relined.

Complex Electronics- If Akai used 1 transistor in a circuit, Sony used 3. This holds true for many Sony models, making troubleshooting of a malfunctioning transport very labor intensive. Sony also suffers on occasion from intermittent transistors, again increasing the difficulty of troubleshooting and repair.  Many Sony decks are also known for bad microswitches that can cause intermittent transport failure as well. There’s no preventative maintenance that can be done to prevent electronics failure, this needs to be addressed as things fail.

Bad Trimpots- the later 3 model decks like the Sony TC756, 758, and even the top of the line TC-880 are known for intermittent and corroded trimpots. For whatever reason, these cannot be cleaned with standard control cleaner, thus any intermittent or noisy trimpot needs to be replaced with a new one. Fortunately, current model replacements are available to replace them.

Bad PC board connectors- several early Sony 3 motor decks, including the TC-650, TC-850 and the TC-854, as well as others  use  PC board edge connectors that the audio and transport modules plug into. It’s not uncommon for these plastic edge connectors to crack, causing poor or no connections to one or more of the cards, which in turn causes transport and audio problems. While the edge connectors can be found online with current replacement models, the installation of them is very labor intensive, figure on an hour to 90 minutes per connector. I tend to write the decks off if more than one connector has failed, as that usually means that more of them will fail down the road.

Broken PC board edge connector- happens in Akai decks as well.