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Aiwa F770 cassette from 1985

Discussion in 'Electronic Repair' started by N Cook, Mar 6, 2007.

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  1. N Cook

    N Cook Guest

    According to the internet a respected deck in its day.
    Had to deal with the slip clutch buried in the mechanism. Photoed before
    disassembly just in case. Reassembled and the 2 pinch wheels were fighting
    one another. A strange pair of springs one acting against the other for the
    "reverse" pinch wheel assembly. I must have put one of these springs back
    with wrong anchor position. Correcting that and its playing and FF and REW
    These units are called 4 head, 4 pairs of screened stereo wires going to the
    head but all seem to relate half the tape. So one question is why 2 pinch
    wheels when there seems to be no proper "reverse" side play or loop control
    function as a fixed head.
    Repeat sends back to replay the same side.
    The "reverse" pinchwheel seems to operate only just clear of the reverse
    capstan spindle and has a strange guide that protrudes around the pinchwheel
    and into the recess of the cassette - what is the function of that
    protrusion and a non pinching pinch wheel ?
    What do the 4 stereo heads do ?
  2. Dave

    Dave Guest

    I think its an ADF 770. Could it be a 3 head model?

    one that can replay the tape while it is being recorded ?
  3. N Cook

    N Cook Guest

    Yes F770 on the front and AD F770 on the back.
    Yes 3 head , presumably one erase head and one double head, 2 motors.
    why would someone need to replay at record - some semi-pro facility for EQ
    checks ?
  4. Guest

    Sounds like a quality cassette deck.

    2 pinchwheels are used to pull the tape taut as it passes over the
    heads. The reuslt is a dramatic increase in reliability of tape to
    head contact, thus eliminating a common cause of poor quality sound.

    4 heads are used so that one can listen to the played back signal
    during recording. This enables several things:
    1. you can adjust the bias and hear the result almost instantly,
    which makes a quality improvement with many tapes
    2. If there is muck on the head, a bad tape, incomplete erase, or any
    other recording problem, you know immediately, and dont waste a lot of
    time making a dud recording.

    Sounds like its well worth fixing.

    As for the pinchwheel protrusion, I dont know what it looks like so
    its impossible to say. Peraps its a small protrusion designed to hold
    the cassette in exactly the right position, cheaper decks often dont
    have accurate cassette shell holding, with predictable inconsistent
    results on tape to head contact and alignment.

    PS all this technology goes back to the 70s, there was a late 70s
    Pioneer that had all the above, and is/was still one of the best
    cassetts decks 20 years later.

  5. bz

    bz Guest

    Could it be an auto reverse deck that reverses when it hits a metal band or
    transparent area of the tape, near the end of the reel?

    One set of heads plays/records in one direction and the other set
    plays/records in the other direction?

    I seem to remember Aiwa had some like that.
    My shop used to work on them in the early 70's (back when I had a shop).

    The strange guide could be a 'tape tension' sensor. It may have been
    disabled at some time in the past to fix some problem.

    Google shows several "Aiwa F770 Three-Head Studio Quality Cassette Deck"
    listings, so the chances are that it is to allow 'sound over' recording by
    playing back and mixing in new audio and then recording that, after the
    sound that was just played is erased.

    One last possiblity, the second pinch roller could be for a second
    recording speed. I seem to remember some machines that played that trick to
    allow multi speed recording.

    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
  6. bz

    bz Guest

    not replay at record. Get the sound currently on the tape off, mix it with
    some new sound and re-record it.

    Les Paul and Mary Ford used to do multi part harmony with just two singers
    and two guitars by such a method.

    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
  7. Rick

    Rick Guest

    When you get to this era - not necessarily. If the deck had any bias
    adjustment control then you needed a three head setup to compare the
    sound coming off the tape to the source in order to tweak the bias
    setting to an optimum position for the tape being used. Funny that my
    TEAC V770 has this option and the model number is so similar to the Awia
    unit here.

  8. clifto

    clifto Guest

    That was an expensive and desirable feature. You knew immediately if there
    were problems, such as badly set record gain, dirty heads, tape path
    problems, etc. etc. Anyone who's ever made an important recording and
    found out at playback time it didn't work would give his auto-reverse
    for this feature.
  9. N Cook

    N Cook Guest

    That explains the multiple heads, the protruding tape guide and the free
    running "pinch wheel" but why a contra-rotating spindle adjascent to it if
    its not used for any reverse play / review function or any function that i
    can see ?
  10. N Cook

    N Cook Guest

    The 2 pinch wheel holders are engaged/disengaged by the same sliding plate
    so the normal one is engaged against the spindle and the "reverse" one is
    close to the contra rotating spindle. There is no possibility of the sliding
    plate to do anything else eg swivel to engage one
    or the other fully.

    The added tape guide is part of the normal swinging mount of a pinch wheel
    but extending around a part of the curve of the pinch wheel so intruding
    into the tape path.

    I'll take some pics tomorrow and upload somewhere.
  11. N Cook

    N Cook Guest

    picture with the odd pinch wheel housing on the left, normal one to the
  12. bz

    bz Guest

  13. b

    b Guest

    bz ha escrito:
    What you have here is a single direction, 3 head tape deck. The
    capstans should both go the same way. If not, you have a capstan belt
    on incorrectly. Try it.

    BTW, the protrusion on the LH pinch roller is a tape guide to ensure
    the tape is fed to the pinch/capstan perfectly straight. In some
    models of more elaborate decks which had both 3 heads AND
    autoreverse, I'm sure i recall having seen it used as the erase head!

  14. N Cook

    N Cook Guest

    I had assumed the low-side wow, when i had the springs set wrong, was due to
    one pinch wheel fighting the other. Perhaps that black plastic tape guide
    was touching the spindle and breaking the whole train , then.
    Both capstans in fact do rotate the same way.
    Surely you can't have 2 flywheels and 2 capstans with pinchwheels engaging
    the same tape, even if connected by the same rubber band.
  15. Guest

  16. N Cook

    N Cook Guest

    I put the deck back in the chassis to check speed and record function.
    If I had not been aware of the features before that i would certainly now on
    It routinely uses playback at record as VU and PPM rather than direct from
    source. So you set to record a signal and nothing appears on the VUs until
    the tape has passed from leader to ferrite.
    Nice to have big numbers etc on a proper large clear and bright cold cathode
  17. Guest

    I dont know the Aiwa one, but typically on this type of deck you can
    switch metering and audio output between record head and play head, so
    you can run it either way.

  18. b

    b Guest

    'Tape-source' switch, usually.
  19. N Cook

    N Cook Guest

    Back to the original problem.
    The belts had dropped off, obviously perished.
    Now , sometimes, on using the power take off to slide up the head carrier
    one of the belts drops off. The one that links the 2 flywheels directly
    together. The first motor to flywheel belt stays on.
    The second belt is driven by a flat pulley driving a vaguely bulbous pulley.
    Belt dimensins of width and thickness are much the same as the originals but
    obviously the length is less than the perished one - try a longer belt ?
    There may be just enough room to add a disc of plastic to the flywheel to
    stop it falling off or putting a static guard in place - any ideas?
  20. b

    b Guest

    N Cook ha escrito:
    I don't understand. have you replaced the belts with new? if so,
    nothing should be falling off and nothing will need modifying.

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