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tape deck speed problems

Discussion in 'Electronic Repair' started by tempus fugit, Jun 19, 2006.

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  1. tempus fugit

    tempus fugit Guest

    Hey all;

    I have 2 tape decks with different speed problems:

    1. Yamaha KX360 - the speed has slowed so that it is roughly one semitone
    below pitch, but is consistent,

    2. Technics RSB18 - speed fluctuates - it seems mostly like it gets slower
    then picks up again, at various points in the tape.


    Any thoughts on how to correct the speed issues on these decks or what I
    might look for? Are there any common causes for this type of behaviour? I
    checked inside the Yamaha and found that it doesn't (unless it eluded me)
    have a speed control on the PC board.

  2. Michael Ware

    Michael Ware Guest

    For the Yamaha, look on the back of the drive motor itself, speed adjustment
    pot may be there.

    For the Technics...lots of thing can slip or bind causing these symptoms,
    try a different cassette if you haven't already
  3. tempus fugit

    tempus fugit Guest

    Thanks Michael - I'll look into the Yamaha. As for the Technics, I've had
    this problem with a few tapes, so I assume that it's not the tape itself.
  4. JR North

    JR North Guest

    The Technics deck will have the speed control in the motor. Loof for a
    small hole in the motor's end plate. Plasic screwdriver now...
  5. Ken G.

    Ken G. Guest

    By now many tape decks are experiancing motor wear out . Try the speed
    adjustement first .
  6. b

    b Guest

    tempus fugit ha escrito:
    the yamaha sounds like a case of adjustment. How old is the technics?
    that sounds like the motor, or more precisely the small controller chip
    inside it. I had to replace the motor on a technics (forget the model)
    which had about 7 years heavy use on it in a radio station (that was
    running too fast and varying).
    Recently saw an early 80s sanyo where the motor would either slow down
    to about half speed (again, varying) all of a sudden , or simply stop.
    In both cases the motor was at fault but you never know - I suggest
    you clean, check braking and gearing and replace belts first.
    good luck
  7. tempus fugit

    tempus fugit Guest

    Great, thanks for all the suggestions guys.

    Michael, the speed adjustment inside the motor did the trick - quick and
    easy repair (for a change). JR - plastic screwdriver? oops I already uses a
    jewellers screwdriver that was metal. Could that cause some problems?

    The technics is a good 25 years old, but hasn't seen a lot of use in the
    past 10 or 15. I'll look into these things that have been suggested here. I
    wonder if maybe the belts are getting a bit worn and stretched too. I should
    also say (to add to the other anwers given here), that I once repaired a
    different Yamaha deck with similar problems as the Technics by replacing a
    few high ESR caps. Took a while to get to that conclusion, but as far as I
    know it did the trick.

    Thanks again
  8. n cook

    n cook Guest

    This is how I calibrate a deck once the speed regulator is found

    Requirements: a 1KHz test tape or a recording of an accurate
    1KHz tone made on a known good tape unit and played back on that machine
    to check, and an audio signal generator
    with a fully floating output ie no dc reference if not then de-couple the
    with a couple of capacitors. Parallel together one channel of the phones
    output of the tape and the output of the sig.gen. and a set of headphones
    in mono (L and R connected). With approximately equal sound levels
    you should get unmistakeable beat note .Reduce the beat to a minimum by
    changing the speed regulation of the cassette unit motor.

    The other tape deck - can be due to anything that moves
  9. Arfa Daily

    Arfa Daily Guest

    That's very novel - I've never heard it done like that. I've got a strobe
    tape that I bought from CPC I think it was, years ago. It has a little
    window in it, and a stobe disc with two rings, one for normal speed and one
    for high speed dub. Very effective. I also have " Clint Eastwood " by The
    Gorillaz recorded on my workshop test tape. This has a very ' natural ' beat
    speed, and I find that I can set tape speed perfectly by ear, just using
    this piece of music. I always check afterwards with the strobe tape, but
    it's uncanny just how accurate the body's sense of timing is.

    Another way I've seen of doing it with a 1kHz test tape, is to just put a
    frequency counter on the end of the deck. Too fast, freq too high. Vice
    versa for too slow.

  10. n cook

    n cook Guest

    You don't even have to have both headphone sound sources anywhere near equal
    level and the beats are still extremely noticable. Putting one source to one
    ear and the other to the other ear to produce beats in your head is not so
  11. tempus fugit

    tempus fugit Guest

    That's a good idea for setting tape speed. Since I'm a musician, I just get
    my guitar in tune to A440, pop in a known good tape, and play along with the
    tape, setting the speed to make sure the pitch is correct.
  12. n cook

    n cook Guest

    Thought experiment.
    Is it possible with my technique to make a test tape using frequency counter
    cross-checked sig gen and one good tape deck.
    If the deck is actually out a bit it will still play back on itself
    correctly methinks.
    Do I require 2 good decks and make a tape on each and try in the other ,
    then unless both are out by the same amount and both up or down by that
    amout then they should all be close to zero beats in all 4 permutations ?
  13. Jim Land

    Jim Land Guest

    You're right, if you record on a slow deck, and it plays back at the same
    slow speed, the tone it plays back will be the correct fequency but you
    won't have a valid test tape. Your analysis of two tape decks is
  14. Arfa Daily

    Arfa Daily Guest

    Yes, I think that the way to do it would be as you say, with the 4
    permutation cross-check. However, these tapes are readily available still, I
    think, already recorded on a known correct speed deck. I have a full set of
    test tones, torque measure, tape path mirror, 0dB record level etc

  15. n cook

    n cook Guest

    It begs the question , how do the manufacturers check the goodness of their
    test tapes?
    I seem to remember a picture in a manual or publication showing via some
    magnetic ink or similar, contrasting bands along a piece of magnetic tape
    carying a constant tone , perhaps they can use that process to physically
    count and measure the visualised bands on a sample of their tapes.
  16. Michael Ware

    Michael Ware Guest

    I remember the standard rate of tape travel over the heads is 2
    inches/second or something. Maybe they check a 'master' deck, mechanically,
    then use it to make master tapes.
  17. Arfa Daily

    Arfa Daily Guest

    I actually went looking on the net for the Konig tapes that I have to see if
    they were still available, and the only reference I could find was in New
    Zealand, so I reckon that I'd better start taking more care of mine ... !!

  18. n cook

    n cook Guest

    I tried that one time making a length of tape in a cassette, length of tape
    from head read position at start to end an exact length for 1 7/8 inches/sec
    , so counting seconds but results did not agree with my commercially
    produced 3.2KHz test tape (stretched?) and didn't explore any more.
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