DVD player - weird problem

Discussion in 'DVD Video' started by Richard Fangnail, Apr 10, 2009.

  1. I have an older Sony DVD player. I just rented a dvd (Slumdog) and
    whenever it displayed the menu or scene selections, a low-pitched hum
    came out of the player itself, as if something was wrong with the
    motor. Sometimes this hum came out when just playing the film.

    I tried two other discs and didn't have that problem. If the problem
    is scratches, why would it cause this? I've never heard the player
    make that noise before.

    If the problem is only with one disc, you'd think the problem would be
    the disc, and yet why would one disc cause that problem??

    When you are just looking at the menu or scene selections for a disc,
    is the disc turning the same way it turns when you are watching the

    Richard Fangnail, Apr 10, 2009
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  2. It is probably wobble due to a slightly out of balance disc. It can also
    be an oversized hole, which is far less likely, however.

    The reason it does it on the menu is because of the menu file's
    location on the disc.

    Take one of those notebook punched hole reinforcement stickers, and
    place it out at the outer edge (on the face not the edge) of the top side
    of the disc. Touch it to your thumb face a few times first so it is not
    so sticky that it is hard to get off... not too much though, it does
    have to stick.

    If the balance improves, you are done. Replace the test sticker with a
    fresh one in that location that has full tackiness. If it gets worse,
    re-orient the placement 180 degrees from the original position, retest,
    and find the correct balance point.
    Archimedes' Lever, Apr 10, 2009
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  3. Thanks for the responses.

    Is the menu/scene selection stuff near the hole or the outside edge of
    the disc?
    Richard Fangnail, Apr 10, 2009

  4. DVDs are not sectored. Speed varies as a function of the physical
    location, with respect to radius, the read head is from the center hub as
    lineal traverse per rotation varies with that location.

    As in CLV. Constant linear velocity. No sectoring needed or utilized.

    Of course, most intelligent folks that claim to have been in the
    industry as long as you do, already know this trivial fact. You must be
    exceptionally... stupid.
    Archimedes' Lever, Apr 11, 2009

  5. I depends on who does the mastering session, and how it got outlined.

    Outer edge is ideal as it spins the disc the slowest. I think discs
    are read from inside to outside though for the movie stream, so even a
    movie would start fast and move toward a slower spin, until it hits the
    layer change which may then read from edge back to the hub so that the
    head doesn't have to transition across the entire disc face after the
    layer change, it can have a short hop to the lead in.

    Leaving a menu up exercises one's player unnecessarily. I put in a
    disc, and play the flic or extras or whatever, and then make sure I
    remove it. Even with the movie stopped on the PS3, it still reads a
    screen shot and some music for the XMB menu on the PS3.

    I think it is a major design flaw to have java run things but be so
    stupid as to not cache the data and let it run from the cache instead of
    the disc, only spinning up the disc and read head when an actual call to
    the disc is made via the menus.
    Archimedes' Lever, Apr 11, 2009

  6. If it has a label on it, of course that is the problem if it is not a
    symmetrical label.

    The only non-symetrical label that can go on a disc is when the label
    is meant for correcting an out of balance disc.
    Archimedes' Lever, Apr 11, 2009

  7. No, idiot. A sectored DVD would be a CAV implementation. There are no
    CAV DVDs.

    CLV discs maintain the same lineal speed throughout the read.
    Archimedes' Lever, Apr 11, 2009
  8. It does, however, have a lot to do with your remarks about why he had
    noise. You were wrong. Period. I was talking about hard sectoring.

    All file systems have soft sectoring, dumbass.
    Archimedes' Lever, Apr 11, 2009
  9. Richard Fangnail

    Franc Zabkar Guest

    Try your disc in a PC DVD ROM drive. Copy the files from the DVD to
    your hard drive while listening for noise. A PC optical drive spins
    must faster than a DVD player, so any out-of-balance condition may be
    easier to detect.

    ISTR the voice coil positioner in an old Philips/Marantz CD player
    moving significantly in a radial direction during the playing of
    certain CDs. There must have been quite a bit of eccentricity for the
    wobble to be noticeable. I don't know if DVDs are manufactured any
    more precisely. Of course eccentricity and balance may be two
    unrelated concerns ...

    - Franc Zabkar
    Franc Zabkar, Apr 12, 2009
  10. There are no "voice coils" in a CD player. ANY of them. There are
    "primary lens positioners" that position the primary lens.

    You should have seen the ones (lens positioners)on the old gas tube
    Laser Disc players.
    They actually did look like a speaker tail assembly.
    It could match up with a resonant point for that one and only disc and
    his player.
    The spectrum that DVDs and newer BD discs are at allow for, and so are
    used, a much finer pit size and track pitch than CD were at. A LOT more.

    You can google for disc capacities and likely find a nice, graphical
    Archimedes' Lever, Apr 12, 2009
  11. Richard Fangnail

    Franc Zabkar Guest

    I have a Philips CD204 which has a "radial motor". This positioner
    consists of two coils rotating around a stationery permanent magnet.

    Page 16 (RHS) of the following Marantz 74CD50 service manual shows the
    circuit for the "radial drive" servo, and page 8 has a mechanical
    drawing of same, although not very clear.

    http://www.audio-circuit.dk/Schematics/Marantz-CD50-cd-sm.pdf (5.3MB)

    The principal is similar to what you see in a hard disc drive, but the
    coil orientation differs. To me it looks like a radial voice coil.
    There is no tracking coil within the laser assembly as there is in
    stepper motor CD players.
    I would think that the track pitch is irrelevant. If the hole is not
    exactly in the centre of the disc, or there is something that is
    preventing the disc from being clamped correctly, then you will see
    eccentricity. The arm of the radial motor will move from side to side,
    much as the tracking coil does in a stepper motor system, although you
    can't see the latter because it is obscured by the spinning disc.
    - Franc Zabkar
    Franc Zabkar, Apr 12, 2009

  12. But they are NOT now, nor have they ever been "voice coils".

    Positioning coils would be as close as you could get to using the term.
    Archimedes' Lever, Apr 12, 2009

  13. It makes for a doubling of capacity. You have no clue.

    Look at a CD with a cheap microscope, then try a DVD.

    There are thousands more tracks on the DVD.

    More is more. Simple math.
    Archimedes' Lever, Apr 12, 2009

  14. No shit. That is why discs are stamped. The die is absolute.

    eccentricities are VERY rare. Coins get mis-struck more often.

    Hot plastic stamping makes ALL discs EXACTLYthe same.
    Archimedes' Lever, Apr 12, 2009
  15. Richard Fangnail

    Franc Zabkar Guest

    The track pitch is completely irrelevant when considering the
    eccentricity of a disc. If a disc is clamped 1mm off-centre, say, then
    the tracking coil or voice coil positioner will wobble 1mm from
    side-to-side. It doesn't matter whether the tracks are 0.1mm wide or 1

    - Franc Zabkar
    Franc Zabkar, Apr 12, 2009
  16. Richard Fangnail

    Franc Zabkar Guest

    One would think so, that's why I suggested that any wobble may be due
    to improper clamping. But the fact remains that I have seen it for

    - Franc Zabkar
    Franc Zabkar, Apr 12, 2009
  17. Richard Fangnail

    Franc Zabkar Guest

    It's a radial motor voice coil positioner.

    The earliest hard drives used a "linear motor voice coil positioner".
    This term appears frequently in various patents, as does "radial
    motor", "voice coil positioner", "voice coil motor", "voice-coil

    See http://www.alasir.com/books/hards/016-018.html

    "Two main types of voice-coil positioner mechanisms are available: •
    Linear voice-coil actuators: • Rotary voice-coil actuators ..."

    The above article refers specifically to hard drives, but the
    principle is the same in the early Marantz CD players.

    - Franc Zabkar
    Franc Zabkar, Apr 12, 2009
  18. If you could even follow a dialog, you would see where he made the
    mistake, and my original reference had nothing to do with eccentricity
    and track pitch. My reference to track pitch related strictly to density,
    but a total retard like you probably couldn't follow that either.
    Archimedes' Lever, Apr 12, 2009
  19. Richard Fangnail

    Franc Zabkar Guest

    During the 1980s I serviced Control Data disc drives to component
    level. This meant cleaning the debris from between the voice coil and
    stationery magnet of BK7 series hard drives after a head crash. This
    involved total disassembly of the affected area. I still have the
    service manuals. They refer to the part as a voice coil. Its diameter
    was the size of a CD.

    Here is what other HD manufacturers have to say on the subject:


    Voice Coil Motor

    An electromagnetic positioning motor in the rigid disc drive similar
    to that used in audio speakers. A wire coil is placed in a stationary
    magnetic field. When a current is passed through the coil, the
    resultant flux causes the coil to move. In a disc drive, the carriage
    assembly is attached to the voice coil motor. Either a straight line
    (linear) or circular (rotary) design may be employed to position the
    heads on the disc's surface.


    Rotary Voice Coil Actuator

    In principle, the rotary voice coil actuator consists of a movable
    wire coil in a stationary magnetic field (similar to the principle of
    a loudspeaker). When there is current flowing through the coil, the
    resulting magnetic field interacting with the permanent magnet causes
    a movement which again acts on the positioning arm. This movement may
    be varied infinitely (linear) with the current strength.


    Low cost and high performance are achieved through the use of a
    rotary voice coil actuator and a closed loop servo system using a
    dedicated servo surface. The innovative MAXTOR rotary voice coil
    actuator provides performance usually achieved only with larger,
    higher powered linear actuators.


    voice coil

    An actuator motor. The force of a magnetic rotary voice coil produces
    a movement of the head that is proportionate to the force exerted by
    the coil.

    - Franc Zabkar
    Franc Zabkar, Apr 12, 2009
  20. Richard Fangnail

    Franc Zabkar Guest

    In a compact disc player, the lens tracks the surface of the disc by
    means of two coils, a focus coil for up-down movement, and a tracking
    coil to side-to-side movement. Coarse positioning is via a worm gear.

    See http://www.repairfaq.org/REPAIR/F_cdfaqa.html

    First, identify the cable leading to the focus and tracking voice coil
    mechanism. This is usually a 4 conductor cable separate from the data
    and laser cable (at least at the pickup end). Disconnect it from the
    mainboard before testing. Using a DMM or VOM, you should be able to
    locate a pair of coils with very low resistance - a few ohms. One of
    these is focus coil and the other is the tracking coil.

    Note that if you have a CD player with a rotary positioner, there may
    be no separate tracking coil as coarse and fine tracking may be

    Here is a reference diagram for a Cheertek DVD chipset:

    Notice the connector pinouts for the Hitachi 1200W optical pickup at
    the top LHS of page 3. You will see Track+, Track-, Focus-, and

    - Franc Zabkar
    Franc Zabkar, Apr 12, 2009
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