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Pinch roller antics

Discussion in 'Electronic Repair' started by mo, Jul 8, 2004.

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  1. mo

    mo Guest

    Pinch rollers in vcrs are often blamed for the tape riding up or down
    the capstan shaft.
    Can some-one explain the mechanics behind this?

    Thanks Mo.
     
  2. The tape may shift around due to issues of parallelism with respect to the
    capstan. Sometimes the rubber is worn, misshapen, cracked, etc. Often
    replacing the pinch roller doesn't even help with skewing problems. Other
    factors like the condition of the capstan, back-tension problems, take-up
    torque, etc figure in as well. Tape skewing problems can be among the most
    vexing.

    Mark Z.
     
  3. sofie

    sofie Guest

    mo:
    Mark's reply was very well said..... yes, tape skewing problems are often
    the most vexing for sure.
    The very first place to start is replacing the pinch roller.... even if it
    looks OK.... replace it first.. In addition to the pinch roller....
    capstan bearings, back-tension, take-up torque (all the things that Mark
    mentioned) ....
    I have seen in VCRs where if the upper drum is worn enough and the ferrite
    head penetration is very shallow that the tape will not slide around the
    drum as easily causing an extra load on the pinch roller and capstan... many
    times resulting in tape skewing, even after the pinch roller is necessarily
    replaced. For this type of repair both the pinch roller and upper drum
    were replaced and that cured the problem. And don't forget to try a
    multitude of test tapes...... a very worn tape or worn cassette shell and
    mechanism can cause these problems too.... especially at the very beginning
    of the tape or at the very end.... where there are extreme differences in
    supply and take up reel speeds and tensions.
    The very last thing we techs want to see a newbie do on a VCR with tape
    skewing problems is to start bending guides, adjusting A/C head tilt,
    bending load arms and levers, etc..... that usually results in a disaster
    or at the very least, a very expensive repair.
     
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