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Induction Magneto Capacitor

Discussion in 'Power Electronics' started by Philsig, Jul 26, 2018.

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  1. Philsig

    Philsig

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    0
    Jul 26, 2018
    Hi, I have old 4 cylinder engine (from the 60's). The induction magneto has a bad capacitor in it ( it's short circuit ) It's written on it 0.3 MFD 400 VDC. I can't find its original replacement. Could i replace it with let say a MF334-400 .33µf 400V Metallized Film Radial Capacitor.

    The original capacitor is a can type capacitor about 1 and a half inches long, half a inch wide. The MF334 is very small in size, will it preform the same job. Is there other value that i should be aware of.

    Thanks
     

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  2. WHONOES

    WHONOES

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    May 20, 2017
    A cap of the same value should be fine. A polypropylene type would be preferable because of their very low dielectric absorption and ability to with withstand high slew rates. Go for the highest voltage type that you can find and fit. Something like 2KV.
     
  3. Philsig

    Philsig

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    0
    Jul 26, 2018
    Thanks for the info.
     
  4. WHONOES

    WHONOES

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    May 20, 2017
    You're welcome.
     
  5. Bluejets

    Bluejets

    4,977
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    Oct 5, 2014
    If it is a points capacitor as I suspect it is, would the x2 cap range be just as acceptable.
     
  6. WHONOES

    WHONOES

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    May 20, 2017
    I think the capacitor even though it is across the points, is intended to resonate with the primary of the ignition coil which will produce a lot of volts.
     
  7. Bluejets

    Bluejets

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    1,045
    Oct 5, 2014
    Ah...ok.
    One wonders though why the original was only rated to 400v.
     
  8. WHONOES

    WHONOES

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    319
    May 20, 2017
    I expect 400V is OK. I just tend to err on the side of overkill sometimes. But I would still go for the highest voltage type that you can accommodate. An X2 type may be OK as they are supposed to be self healing if I remember correctly.
     
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