Can bipolar capacitors be used instead of polar capacitors?

Discussion in 'DIY' started by birchoak, Jun 21, 2018.

  1. birchoak

    birchoak Hi-Fi Nut Subscriber

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    Sort of a hypothetical question, for a friend of mine (not me! I would never ask something as foolish as this). Say he pulled a capacitor out of an amp and did not note which direction the negative leg faced. The schematic is a lousy copy and, well, he kind of screwed up because he was riding a 60/40 rosin core high. Could you simply order a bipolar capacitor in the appropriate uF/V and have done with it? No guessing, no tears? Why doesn't everybody use bipolar capacitors? Wouldn't that make things easier?
     

     

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  2. Scott75s1974

    Scott75s1974 Member

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    I'll defer to the experts, but I've been told that bipolar's are useful in the signal path. I've followed such advice in a recap and they work wonderfully to my ear.

    You don't need a super clear schematic to figure out if its signal or power. If the schematic is not helping, consider looking at the board. Is it in the regulator section, or an audio section? If the former, you need a polar.

    On my receiver, the power caps were sometimes given a different number series. (power was 601, 602, signal was 1/101; 2/102, etc.)

    If its part of a signal circuit (amp, tone board, etc.) then check and see if it's has a twin. That might help guide you in figuring out proper orientation.

    If it doesn't have a twin, then...I'm thinking...it's probably not a signal path cap...and prob needs to be polar. If it needs to be polar. Trace both pads to see if one lands on a positive or negative rail, that will give you your orientation answer.

    But I've also read that bipolar will revert to polar when used in a polar situation. But I defer massively to others on that point.
     
  3. Blue Shadow

    Blue Shadow I gotta get me a new title

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    Bipolars are double caps and cost a good bit more. for a manufacturer that is a significant cost and would raise the price of the gear.

    Look for google images of the board for orientation of the cap. works if it is a popular unit that gets recapped. If not there, ask here with more info to determine proper orientation.

    Or just wait for someone that knows for sure a bipolar cap will work.
     
  4. mbz

    mbz AK Subscriber Subscriber

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    A bipolar cap same uf/V will work equally as well as the polar however it will be more expensive.
    I think it would be a simple task to work out what each pin connects to, ie, Rxxx and Dxxx,, and
    work out the orientation from the schematic
     
  5. avionic

    avionic " Black Knights " Subscriber

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    It would be pretty easy to determine which pin is more positive than the other.
     
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  6. jeromach

    jeromach With sufficient thrust, ducks fly just fine

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    True, just mount it, if it blows you put in the next one the other way around...

    Stay out of the way though, for a couple of minutes!

    :D
     
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  7. Scott75s1974

    Scott75s1974 Member

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    A question: would it be possible/wise to momentarily power up a circuit with the cap out (using a DBT) and take a polarity measurement of the empty pads?
    Is there some scenario where this would do major harm?
     
  8. Bob

    Bob AK Subscriber Subscriber

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    bipolars are wonderful for a number of reasons. they fit forwards and backwards for those
    who are time-challenged. they tend to be higher on the sound-quality ladder - like the
    Nichicon MUSE ES. they are green to show off how golden your ears (maybe wallet)
    are. and lastly, buying them removes the possibility of buying cheap/bad polarized caps.

    cost, gotta look at the big picture. 47uf/35v Nichicons. Fine Gold (FG) is 47cents, ES is 66 cents
    that's 19 cents or if you buy more than 10 - then the difference is 14 cents. peanuts
    said Charlie Brown.

    now take 30 of them (on average - we'll get to some other facts), and the difference is now
    only $4.20 to $6.00 on an order of about $15. won't disturb weekend beer money.

    I'd spend the extra money if for no other reason than its the biggest return for bragging rights,
    and more $$ for flippers who market over the flippers who just wipe it clean (maybe)

    however, bipolars are limiting in size (fatter and taller), and most importantly don't go up
    in value for PS usage (the Muse ES is limited to about 470uf from what I recall).

    and does a really good job until you move into the films and the VCap/Russian Teflons.

    recap and enjoy the music
     
  9. Retrovert

    Retrovert AK Subscriber Subscriber

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    For the price of the NPE one could just use a film capacitor which is a better choice as it lacks the high ESR/ESL of electrolytics, does not have a limited lifespan, does not have rectification distortion, and has far more linear characteristics.

    As others have noted, it is trivial to determine the polarity for the circuit.
     
  10. mbz

    mbz AK Subscriber Subscriber

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    Point taken about the limiting range. Nichicon UEP is my preferred choice for bipolar PS.
    Sizes include 1000uf/35V, 2200uf/25V...
     
  11. birchoak

    birchoak Hi-Fi Nut Subscriber

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    So, if I use some 1uF 50V bipolar caps instead of 1uF 50V polar caps in a power amp, nothing bad will happen? I honestly don't mind paying the extra money as this is not a business and I sometimes make mistakes installing caps backwards. It happens. Plus, I have a bunch of bipolar caps on my bench.
     

     

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  12. birchoak

    birchoak Hi-Fi Nut Subscriber

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    Better to use film caps all around? If they last longer and are better I will pay for them and put them in. Are film caps a no-brainer?
     
  13. birchoak

    birchoak Hi-Fi Nut Subscriber

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    Yes, please answer this question for us!
     
  14. mbz

    mbz AK Subscriber Subscriber

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    +1

    Don't know why this is even been considered.
    Generally, parts should not be removed (even on dbt) without some sort of analysis of the impact.
    A 1uf/50V psu cap will almost certainly be for a noise path, so no drama. I would trace what components
    are connected to each pin and refer to the schematic. Only basic skills are required to do this. If you
    list the amp make/model or extract of the schematic an AK member will give you a safer answer.
     
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  15. Goldie99

    Goldie99 Well-Known Member

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    Agree with mbz - just list the amp make / model, or extract of the schematic, and someone can tell you exactly what's needed.
     
  16. birchoak

    birchoak Hi-Fi Nut Subscriber

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    It is a Proton D1200 power amplifier. I compiled a list of electrolytic caps needed, based on the SM (something I haven't done before--I've always gone by the actual components installed in a unit). Lo and behold, many of the caps I ordered seem to have significantly different values from what I've been pulling out. I know that I am an unwashed amateur and that many of my questions are probably annoying/baffling/etc., but I figure this is the place to ask them--I can read about electronics theory on my own but there are some nuts and bolts questions I dare to ask here. For example, AK member Avionic kindly pointed out that I could safely use a 160V cap instead of an unobtanium 120V cap--
     

     

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  17. mbz

    mbz AK Subscriber Subscriber

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    Misread, the 1uf/50V is not in the psu. The service manual
    lists the following 1uf/50V caps,
    C609,610 bipolar, L&R audio path
    C623,624, L&R Bias circuit
    C707 protection
    C807 LEDs

    The sm artwork shows the orientation of these caps, markings
    appear correct.

    Proton.JPG
     
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  18. sKiZo

    sKiZo Hates received: 8641 Subscriber

    Standard polarized capacitors are inherently non-linear.
    (Huh?)

    Without getting into the gory details, way I understand it ... the "perfect" audio circuit is linear, where the voltage remains consistently equal to the charge throughout the path. Bipolar capacitors are linear, and the end result is improved accuracy and less output inconsistencies, greater stability, and less fluctuation. Especially nice in line level circuits, but also handy for reducing noise in power circuits.
     
  19. adpopulum

    adpopulum Well-Known Member

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    With due respect It ain't trivial, it might be simple or easy but it is the farthest thing from trivial.
     
    Last edited: Jun 30, 2018
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  20. birchoak

    birchoak Hi-Fi Nut Subscriber

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    I couldn't wait, and I love those shiny green bipolars so I put them in. Amp fired right up through a DBT so that's test one passed. I will hook up to "normal" power and play some music. Also, what Proton actually installed in this particular specimen is very different from the SM--examples:

    1) Instead of ceramic 0.47uF 50V caps at C669-C670, Proton installed a pair of 10uF 16V bipolar electrolytic caps in this location.
    2) Instead of ceramic 0.1uF 100V caps at C631-C634, 1uF 160V caps were used.
    3) SM specifies bipolar 1uF 50V caps at C609-C610 but there are absolutely no caps on this board, just empty spaces.
    4) SM details offset alignment, but there are no trimmer installed at VR601 & VR602--just empty spaces!

    As a rookie, I find these changes a bit confusing and wonder how the amp operates at all if some of the parts used differ so wildly in uF (I know as long as V is the same or higher a cap can probably be substituted provided you do not stray more than 10% from uF value). But 10uF 16V substituted for 0.47uF 50V? How can that part work there? So, using bipolar 1uF 50V caps instead of polar 1uF 50V caps seemed pretty insignificant in the vast scheme of things on the Proton. Also, I know the four 15000uF 120V caps will eventually die and this will become an attractive paperweight, as I am not willing to spend $400 on new caps, no matter how much I like this amp! Like me, this amp is renting time on this planet.
     

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