Yamaha K-640 Auto Reverse Cassette Deck - Tested and Working Great

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Folks have been asking for a reasonably priced tape deck for some time. We sell tons of Nakamichi Dragons and CR-7a's but restored versions are super expensive.

Here we have a nice survivor that arrived working brilliantly. I played back and recorded a tape with no issues whatsoever.

The front display is super bright and clear, and all transport functions are quick and responsive.

Cosmetically it's nice showing slight signs of use.

Recommended Cables:

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best 

The SkyFi Testing Process for Tape Decks and Reel to Reel Machines:

First steps are performed to determine if the unit is a candidate for our full restoration process or if its just in need of a light service.

We first do a  basic functionality test to ensure proper playback fast forward and rewind.  We look for smooth operation of the motors, transport engagement and associated rolling parts.  

We then do an internal physical inspection to ensure the belts and rubber consumable parts are up to spec.  

Internal components are checked to make sure that there are no signs of heat stress or damage particularly in the power supply section.  Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR. 

A light service will involve replacement of belts and rollers, external cleaning of heads, mechanism and boards and basic record and playback tests.  

A full restoration will often include disassembly of the drive system and replacement of all consumable and wearable parts including pinch rollers, belts, brakes, bearings.  We then clean lubricate and re-assembly the drive and perform basic mechanical alignment to ensure proper tape path and head alignment. 

Final calibration will involved adjustment of playback erase and record heads and optimization of the bias for a specific tape type.  We do this with the aid of a  Soundtech 1510A tape deck analyzer and a Nakamichi T100 unit and reference calibration tapes.  

Final listening tests are done while monitoring with our reference Grado HP1 headphones and a variety of factory and custom reference recordings.  We find that there is no better system for critical listening on tapes than the headphones specially when comparing a live feed to a recorded feed.