Sony TC-D5 Pro: plays commercial tapes fine, but slows down with new Philips ferro blanks

Discussion in 'Tech talk' started by jvlobo, Jul 17, 2026.

  1. jvlobo

    jvlobo New Member

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    Hi everyone,

    I've just restored a Sony TC-D5 Pro: new speaker, all 3 belts replaced (new kit from phonohifishop), gears cleaned and greased. The pinch roller is original but looks in good shape, not glazed.

    The situation:
    • Commercial pre-recorded cassettes from the 80s/90s play fine.
    • Brand new Philips Type 1 Ferro blanks slow down after a few seconds of play. I tested two sealed tapes and both do the same.
    • Interesting detail: the tape runs fine over the clear leader and for a moment at the start of the brown tape, then the slowdown begins.
    • The same Philips tape plays fine in a cheap Sony TCM-939 cassette-corder.
    • Fast-forwarding and rewinding the full tape didn't help.
    I'm attaching videos showing the behaviour.

    Old tape playing good:


    New tape slowing down (front):


    New tape slowing down (gears):


    Is this normal for a healthy TC-D5, or does it suggest my motor/speed regulator is weak under load? Should a good TC-D5 handle these modern blanks?

    Any experience with these decks and modern tape would be very appreciated. Thanks!
     
  2. Valentin

    Valentin Well-Known Member

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    Don't think the tape has any problem. Even with the pre-recorded tape the speed jumps quite a bit and it's audible. It's just that the pre-recorded has a different formulation which is not as slippery.
    To me it looks like a polished capstan problem, as in third video it can be seen motor and flywheel are still rotating, but tape is not moving.

    I would proceed with etching the capstan with ferric chloride: whiile rotating in REW keep a cotton swab soaked in substance against the capstan (area that comes in contact with tape).
    Clean with IPA both capstan and roller after.
     
  3. jvlobo

    jvlobo New Member

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    Thanks for the advice! Didn't know about that, I'll try
    Would this one work? https://www.biolaboratorium.com/en/products/eisenchlorid-37-100ml-biomus
    Thanks!
     
  4. Mister X

    Mister X Moderator Staff Member

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    In case the capstan is harder than normal, I've used Rubber Renue to soften it up. Sometimes it lasts awhile, sometimes it helps with finding problems before getting replacement rubber.

    upload_2026-7-18_13-27-48.png
     
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  5. Valentin

    Valentin Well-Known Member

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    @jvlobo That product look good for the job yes.
    Rubber Renue is good for rubber things, there's also a similar one in Europe called Nowa Guma which does the same thing.
    But for the most part if roller isn't glazed or hard as a rock I wouldn't suspect it.
     
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  6. jvlobo

    jvlobo New Member

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    Awesome, thanks guys.
    I think I'll try the ferric chloride first and see what happens, if it doesn't solve I'll put my attention on the rubber parts.
    I'll let you know how it goes.
     

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