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DCC capstan howl?

Discussion in 'Electronic Repair' started by dotter, May 6, 2007.

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  1. dotter

    dotter Guest

    Hi All,

    I'm attempting to repair a high end DCC recorder (Philips DCC900), the
    fault only seems to affect DCC tapes not normal cassettes...

    On playback there is a high pitched howl, suprisingly load from the
    transport mechanism, loading the capstan flywheel (with my finger, to
    slow it down) didn't make much difference, pulling the rubber pich
    roller away also made no difference.

    When the transport is howling the audio level goes to zero.

    For a while, the sequence of rewind, stop, play -> howl, if followed by
    a stop and play then the howl went away.

    This doesn't happen when the cassete is removed or using a regular
    cassette, different DCC tapes also howl.

    If I press the tape lightly while playing in one corner the howling stops.

    All help welcome, I'm trying to sort this out for an elderly neighbour
    who has a large collection of DCC tapes.

  2. First I would look for a mechanical slippage.
  3. Guest

    Sounds like bad bearnings.

  4. Ian Jackson

    Ian Jackson Guest

    I had a similar howling problem. Certain tapes were worse than others,
    and it depended how far through the tape you were playing.

    It was caused by the slipping clutch on the take-up capstan. Instead of
    slipping, it's actually oscillating between stop and go, hence the
    howling sound (a bit like producing a note with a wine glass).

    Many clutches have a simple torque adjustment. Changing the torque MAY
    stop the howling. There are three spring fingers pressing onto a
    'stepped' part of the underside of the take-up wheel. You adjust the
    torque by rotating the spring fingers onto the next step.

  5. I'm attempting to repair a high end DCC recorder (Philips DCC900), the
    Thanks to all who replied - much appreciated.

    I've given the captan bearings a good lube but unfortunately there
    doesn't seem to be any way to adjust the torque on the take-up clutch.

    The clutch seems to consist of a disk of felt between two plastic disks,
    I tried wetting the felt if only to change the characteristics of the
    system but with no improvement, possibly worse - but very variable :(

    The number of moving parts is limited so resigned myself to "toucing"
    all of them in some way but the deck ony seems to dismantle "easily" to
    a certain level, I can't get the take-up sprockets apart - very
    disappointing :( :(
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