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dual capstan cassette deck tape curling problem

Discussion in 'Electronic Repair' started by p.h., Mar 20, 2008.

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  1. p.h.

    p.h. Guest

    Hi!

    I have a problem with dual capstan cassette deck - some tapes get curled
    just before supply capstan. It happens only during first 1-2 minutes at
    the very beginning of a tape. The tape is damaged. It happens for let
    say 2 out of 30 tapes. The tapes are good, there were no problems with
    them for many years they were played back on various cassette decks and
    players.
    For some tapes there are moments they are sounding as if they were
    squashed earlier, although they never have been. I have noted it on
    prerecorded tapes.
    Tape length seems not to influence the problem - 120 minute tape is
    played back correctly.

    I have tried to adjust depth of the supply pinch roller, but I was
    unable to adjust it so all cassettes could be played without the problem.

    The second dual capstan deck I have bought have the same problem, but
    with different tapes.

    Was it a common problem for dual capstan decks? What would you advise me
    to do to fix it?
     
  2. bz

    bz Guest

    It sounds like the capstan and/or pinch roller may not be parallel to each
    other and perpendicular to the base plate of the player.
    Perhaps a screw is loose somewhere? Perhaps some of the bearings have
    become worn, allowing one of the shafts to
    change the alignment.

    Make sure that none of the mechanisms are bent or badly worn.

    Look for excessive movement for any part of the mechanism.

    See if the vertical position of the tape in the cassette and of the
    cassette itself, makes a difference.





    --
    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  3. Tim Schwartz

    Tim Schwartz Guest

    Hello,

    The first thing I'd suggest to check it both the take up torque and the
    back tension (hold back) torque. This require the proper gauge, and
    knowing the factory spec for your machine.

    I've also seen deteriorated pinch rollers cause all sorts of problems,
    as the rubber gets harder with age and does not conform to the capstan
    shaft as it should. Serious head wear can also contribute, as it
    reduces the pressure of the head against the pad in the cassette and
    somewhat changes the tape path.

    If there are serious grooves in the heads from wear, then you can no
    longer adjust the head block, as moving the head with groves in it will
    likely cause tape edge damage. Even peaking the azimuth can cause
    problems.

    Adjusting the heights of things is the last thing I would have tried,
    as it usually causes more problems than it cures, and it is very
    difficult to get things back to where they were.

    I'd start with the torques. If you post what you find, please include
    the make and model of your deck.

    Regards,
    Tim Schwartz
    Bristol Electronics
     
  4. Eric

    Eric Guest

    You need a mirror tape to check the tape path and the alignment gauge plate
    to align the entire tape path. TEAC still selling the alignment gauge for
    $2000.
     
  5. p.h.

    p.h. Guest

    Thank you very much guys. I appreciate your help.

    I've managed to fix the problem. The first dual capstan deck was Sony
    TC-K690 and the second one, the one I still have, is Sony TC-K750ES.

    In both decks I've cleaned rollers and heads immediately after first
    turning them on. I've used salicyl alcohol and plastic sticks
    encovered with cotton wool. After that I had started using the decks
    and found problems with tapes curling I have mentioned before.

    Just a few days ago I have noticed that supply pinch roller of the TC-
    K750ES I still have has white spots on the outer side, so I have
    cleaned that roller once again. As I wasn't able to clean it using
    salicyl alcohol alone I have carefully used nail-file.

    After that I have tested how the deck's mechanism behaves on the
    problematic tapes and found out that the problem disappeared.

    I don't know what formed the white spots; maybe they were formed by
    salicylates(?) I have cleaned the roller one more time, but this time
    using isopropanol to ensure there won't be any further surprises.

    I think it would be a good idea to replace both pinch rollers as their
    surface has microscopic cracks.

    Anyhow - I am glad it works now.
     
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