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Non-polarised electrolytic capacitors needed!

Discussion in 'Electronic Repair' started by Adrian Brentnall, Dec 5, 2004.

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  1. HI All

    I need a quantity of non-polarised Electrolytic caps, radial-ended, in
    order to re-cap an old Lowrey electronic organ.

    According to the parts list the original components are 3uF / 20V -
    but something near to this (maybe 4.7u) would do - likewise the
    voltage rating - but component size is fairly important as the
    replacements need to fit in place of the originals (5mm diameter /
    11mm long).

    There's one of these components for every key on the upper manual -
    they control key sustain - so about 40 would do nicely.

    I can find a 3.3uf / 100V at 34p per 5 (www.cpc.co.uk) - wonder if
    anybody knows of any alternative UK suppliers, tried Maplin & RS
    without success..... any other suggestions please ?

    TIA
    Adrian
    Suffolk UK
     
  2. Harvey

    Harvey Guest

    Rapid Electronics do a range of non-polarised here
    http://www.rapidelectronics.co.uk/r...CAT_CODE=31198&STK_PROD_CODE=M62536&XPAGENO=1

    (from http://www.rapidelectronics.co.uk/) - they do a 4u7 35v in a case size
    of 11 x 5mm for £0.048, or cheaper in quantity.
    They also do a 3u3 100V in a case that's 11 x 6mm for 7p each (or 6.4p if
    you want 40) - but I'm not sure how well a 100V rated non-polarised would
    behave with less than 20V on it.
     
  3. JURB6006

    JURB6006 Guest

    Since no doubt you're doing this for sound quality reasons, might I suggest you
    consider better caps, like the poly dipped kind, or maybe those designed for
    high end speaker crossovers.

    Not only should they last longer, but they'll likely have lower ESR and the
    capacitance will be more accurate. If this thing is older, lytics weren't quite
    as small back then and you might just be able to fit them in the space you
    have. Another reason for doing this is that electrolytics caps of the newer
    type seem to be a pariah to the equipment in which they're installed.

    Having designed and built a few amps, I avoid using electrolytics in the audio
    path like the plague. Only if and when nessecary. Of course I'm going to use
    them for power supply filters, but in the audio path I think they're bad news.

    Even if you wind up using 'lytics, try to find some good ones, i.e. not the
    kind they use in TVs. Possibly you could talk to someone at a local high-end
    audio repair facility. They would know more about where to get such parts in
    your area.

    JURB
     
  4. HI Harvey
    Many thanks - looks like Rapid are the ones - reasonably priced as
    well - wonderful !

    I'm not sure what the likely effect are of running an electrolytic at
    1/5 of rated voltage.......... so probably best to go for the 35V
    ones.

    These caps are in a pretty undemanding circuit - they provide a
    sustain effect by charging & discharging through a couple of diodes -
    so as long as they're all the same (nominal!) value - then the exact
    value isn't critical......

    I've had three or four of them fail so far - so it seems like a good
    time to change the lot of them - perhaps the organ will run for
    another 30 years after that !

    Many thanks
    Adrian
    Suffolk UK
     
  5. HI Jurb
    Thanks for the comments

    I'm not really convinced in this particular case - I're rather
    restore to original spec. instead of 'improving' things - I should
    really be spending the time practicing my organ playing rather than
    tinkering anyway !
    These caps provide a simple 'sustain' effect by effectively keeping
    the line associated with a particular key / note "pressed" once it has
    been physically released. No doubt it would be ideal if they were all
    exactly the same value - but I'm not about to sort through a bin of
    C's in order to find 40 matched components!
    I've found a local supplier - I guess I can always re-cap an octave of
    the keyboard and satisfy myself that it's working OK before commiting
    to all 40 notes <g>

    Many thanks for your comments
    Adrian
    Suffolk UK
     
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