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Tape head demagnetization

Discussion in 'Electronic Repair' started by hr(bob) [email protected], Nov 24, 2012.

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  1. hr(bob)

    hr(bob) Guest

    My car (built-in) tape player seems to be getting strange in its
    volume. Associated radio is fine, tape volume is down. I thought
    that I should demag the tale head. But, the opening is only barely
    big enough to insert a tape, and my 120V 60Hz demagger has a 1/2" long
    tip at 1/3" diameter, affixed on the end of a tube that is at least 1"
    diameter so there is no way to get the demagger tip anywhere near the
    tape head. I could maybe tape a large nail to the end of the existing
    tip, and reach the vicinity of the head, but I don't think that will
    so anything. I don't know what the magnetic structure is under/inside
    the head, but assume it is shaped to deliberately have flux going
    outside the head. It's not worth it to make a coil small enough to
    fit into the opening. I understand there are demagnetizing tapes
    available, but I am cheap and don't want to spring for the $$ unless I
    am reasonably (66+%) sure it will work.

    Thoughts, ideas, polite suggestions.
  2. A magnetized head will cause loss of high frequencies long before there's a
    drop in volume.

    The deck probably has some other problem.
  3. hr(bob)

    hr(bob) Guest

    Thanks Bill and Gareth,

    OK - that's two votes against demagnetizing, plus I was skeptical
    myself. So, now I have to decide whether to move my tapes to CD's, or
    tear into a 10 year old car radio/tape player /cd player. I think it
    will be easier to move a few tapes to CDs than tear up the car radio.
  4. tuinkabouter

    tuinkabouter Guest

    First check the tape on a known good tape player.
    Or use a original prerecorded tape.

    Tapes recorded on a machine with bad aligned heads will play good on
    that machine, but not on others.

    Clean the head. Clean the tape guides.
    Demag if you can.
    Adjust the head in height for maximum output.
    Adjust the head azimuth to maximize high frequency.
    And repeat the last two.

    A magnetized head will destroy all your tapes (bad signal to noise
    ratio). And can not be undone.
  5. Robert Macy

    Robert Macy Guest

    loss of volume? doesn't that mean gunk building up that keeps the tape
    too far away form the head? Or, mean some component is lost? like a
    coupling cap that has seen better days? Or, something as simple as
    one of the wiring connections in the cabling has gone high resistance.

    Sadly, my favorite tapes were made during the era of poor mylar
    coating and have all turned 'squeaky' and unplayable! I wish I could
    have transferred them before they died, but hindsight.
  6. mike

    mike Guest

    I'd give up on head demagnetizing. It's not likely the problem.
    And you're more likely to magnetize it with the demagnetizer
    unless you disassemble the thing so you can get at it.

    Tape players don't last in cars.
    I've only had two CD players and they were worse.
    The heat, outgassing of plastics, dirt, etc. get all over the optical
    and mechanical stuff.
    Luckily, my last player has a USB slot and a Flash Card slot.
    It won't play a CD any more, but the SD card works fine.

    As for old tapes...
    If you have rare music, you're pretty much screwed.
    If you have popular stuff, there's an option.
    Go to the library, check out a CD. Copy it back to the tape.
    If you bought the tape, you own the license to play it.
    The nitpickers will argue about it, but I think you're
    on solid moral and legal ground to refresh the media.

  7. Sounds like very dirty heads , or head alignment has gone out of whack. This
    happens when one or both head mounting screws loosen. Happens occasionally.

    Mark Z.
  8. Charlie+

    Charlie+ Guest

    On Sat, 24 Nov 2012 16:35:30 -0800 (PST), Robert Macy

    A trick I found for this squeaky problem to do a one time transfer was
    to play them as cold as possible, unfortunately just freezing the tapes
    doesnt last long enough - always thaught a head heatsink to a
    deepfrozen al or cu block might do the trick but I never tried it!! I
    just caught mine early enough! Mine were BASF :(
  9. RipeCrisbies

    RipeCrisbies Guest

    As others have said, this does not appear to be a magnetised head but it
    could be that particles from your tapes has collected in the gap(s) on
    the the tape head(s). The gap(s) need to be magnetically open so that the
    passing tape completes the magnetic circuit and it is a very small gap on
    a playback head (of the order of 0.0001 inch).

    BTW, if you are using a head demagnetiser never switch it on or off
    anywhere near the heads. Move a few feet away before switching off. One
    spike and you will have magnetised them!

    Many years ago I worked in the dev lab of Marriott Magnetics one of the
    original makers of tape heads in the UK. Long gone.



    Sales @ radiowymsey
  10. I'd clean the head and capstan first, then worry about degaussing things.
  11. josephkk

    josephkk Guest

    Once upon a time i had a battery powered cassette sized tape head
    demagnetizer. Sounds like just the trick for your situation, to determine
    if it is head magnetization (perhaps unlikely) or some other problem.

  12. josephkk

    josephkk Guest

    Lucky you are, over 200 to transfer have i.

  13. josephkk

    josephkk Guest

    Depending on your tastes, some might be available now in CD or MP3 format.
    You may have to buy a lot more than what you have to get all you want. I
    have a lot of old music of the 1950s to 1970s range and an interesting bit
    outside that range. Not all digital yet. You know how to find me.

  14. josephkk

    josephkk Guest

    (+1) on the dirty heads. I had forgotten.

  15. Robert Macy

    Robert Macy Guest

    Wow! Great tidbit!
  16. Franc Zabkar

    Franc Zabkar Guest

    Just to offer a different perspective, I onced repaired a Fujitsu Ten
    auto-reverse car cassette player with the same symptom as yours. The
    problem turned out to be a small dirty multipole switch. I'm a bit
    hazy on the details, but ISTR that there were two head circuits, and a
    different circuit was selected in forward and reverse mode.

    As for demagnetising the head, I have a cassette tape with a built-in
    battery powered demagnetiser that automatically activates when you
    press the play button while the player is unpowered.

    It looks something like this ...

    - Franc Zabkar
  17. gregz

    gregz Guest

    Also true of a dirty head for the most part with possible left right
    A magnetized head can ruin tapes HF.

  18. legg

    legg Guest

    Much of the audible 'squeek' noise may be the fault of the housing,
    rather than the tape itself. Transfering the reels to a new case may
    fix that. Labels can also be transfered, if the fix works.

    In some instances, the case was defective on first transfer, so the
    audible jitter was included in that transfer - no way around this.

  19. Rene

    Rene Guest

    You mention the capstan, I would also check the rubber roll very
    carefully. After years it often gets little tears in the rubber and it
    may be deformed and therefor not be guiding the tape correctly anymore.
    They are cheap and relatively easy to replace.

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