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Thread: 40+ year old motor run capacitors

  1. #1
    Join Date: Sep 2009

    Location: Derbyshire

    Posts: 9,228
    I'm Josie.

    Default 40+ year old motor run capacitors

    Hi all.

    I've recently replaced some motor run capacitors in my reel to reel.

    The old ones were made by Bosch and I think they date from 1973/75 from which I took from numbers printed on the side or each capacitor.

    They are 10uf, 8uf and 20uf.

    I was advised to replace them as they could leak. I can't see any leakage as such though.

    Is there a way of testing them and if they still come up to spec, is it worth using them or should they be replaced anyway?

    Thanks
    Last edited by The Black Adder; 05-02-2019 at 10:53.
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  2. #2
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 9,302
    I'm Andrew.

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    Any cheap volt meter should be able to check resistance
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  3. #3
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,089
    I'm Alan.

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    Not so simple Andy. With high voltage capacitors you really need a high voltage tset to as a multimeter doesn't stress the cap enough.

  4. #4
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

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    they need to be discharged and disconnected before testing(you might get a biggish spark if they have charge in them. short the terminals together with a screwdriver. leads are usually slide on)... an analogue meter is best. reading should go quickly towards 0 then drift up slowly. use a higish setting..10k range or so. you can use a digital one tho if all you have but i wouldnt.
    Regards,
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  5. #5
    Join Date: Apr 2012

    Location: London

    Posts: 685
    I'm James.

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    I've had a 500V oil filled polypropylene Bosch vent in a PSU recently. It was one of four, all looked clean before this. The other three measure perfectly up to 350V which is the limit of my test rig. I changed them all anyway, the mess wasn't fun to clean up, not worth the worry IMO. If they measure well at or near spec voltage you can always use them elsewhere but at an appropriately derated voltage?

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  6. #6
    Join Date: Feb 2013

    Location: W Lothian

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    I'm Grant.

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    yup, i'd be inclined to just change them too. can always keep for spares etc if ok.
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -

    Oh my god! There's nothing wrong with the bidet is there?

    “Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".

    “You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”

    "You don't have free will. You have the appearance of free will.”

    “There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”


    ***SMILE, BE HAPPY***

  7. #7
    Join Date: Sep 2009

    Location: Derbyshire

    Posts: 9,228
    I'm Josie.

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    Cool, thanks guys.

    I don't have any kit to test them. Would be interested in knowing if they are still up to spec though.

    Changed them out anyway. Been advised to do so and I everything works fine.

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