capacitor polarity

Discussion in 'General Electronics Chat' started by spankey666, Jul 5, 2013.

  1. spankey666

    Thread Starter Member

    Nov 30, 2011
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    i have just aquired some of these click
    and i am unsure of the polarity. there is a white band with arrows but no - markings. i presume this still means it is the negative but just require confirmation.
    Thanks in advance
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    A golden rule for electrolytes(metal can type) in the older days. Was that the can was always connected to the negative pole. And that the markings was always on negative pole. I have not seen any other standrad yet
     
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  3. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Yes, if that white band down the left side has arrows/dashes in it, that likely indicates the negative side.
     
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  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    And when electro caps are new, they have a long + leg, and a shorter - leg. :)
     
  5. WBahn

    Moderator

    Mar 31, 2012
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    Can you post a picture of what you are actually seeing. I suspect that there will be something there that is the negative sign but that you are seeing as something else.
     
  6. spankey666

    Thread Starter Member

    Nov 30, 2011
    91
    3
    the legs were the same length , i kinda knew the answer but just wanted reassurance :)
    there is definitely no other markings, but i soldered them up and put them to use and all is ok. it was just a little worry as i have a board containing 50 of them and that would make a big noise and a lot of smoke if i got it wrong lol

    thank you everyone who replied.
     
  7. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    The large gray stripe (barely visible on the far left of the cap in this image) shows the negative pole:

    [​IMG]

    Quite honestly, I would not have gone for these caps. A cheap chinese brand, only rated at 85C and not a low-ESR type is just asking for them to die, even if connected correctly and used under normal conditions. Sadly I've seen many broken electronics come in and the problem ends up being bad caps, a lot of them are G-Luxon. I even heard about someone with a motherboard that used these caps, and almost every one of them was blown. I guess it depends on your exact application though, and the environment in which it will be used. Just be prepared for them to explode under normal operation. Keep yourself and others safe, and be ready to replace them with decent 105C rated Rubycon, Panasonic, Nippon, or Nichicon capacitors.

    Best of luck to you!
    Matt
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Depends if the Chinese caps are this type;

    [​IMG]

    :eek:
     
  9. MrChips

    Moderator

    Oct 2, 2009
    12,452
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    What? How can they try to masquerade a 2200μF cap as 6800μF?
    That has got to be the worst fraud in electronic manufacturing.
     
  10. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Even if they don't do that, G-luxon caps are no good.
     
  11. wayneh

    Expert

    Sep 9, 2010
    12,156
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    Is that for real? Sort of funny if it's a hoax. If not, the shocking part is that they 1. have the gaul to do this and 2. that they seek to profit on the tiny spread in value between the smaller cap + fraudulent package and just using a larger cap. How could you hope to run this scam long enough to make any money?
     
  12. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Even worse, it appears that the outside is rated at 50 volts, actual part at 35 ... That's serious trouble.
     
  13. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Usually these scams are found in ebay postings from users with poor repute. They are avoidable provided the buyer checks the seller's ratings and comments, etc.

    However, some capacitors are just poorly made. Samxon, G-Luxon, Capxon, Raycon, and more. Just about any capacitor with an "X" in the brand name will be junk. Any non-english sounding brand tends to be rubbish as well, though that may be over-generalized. My point still stands, though.
     
  14. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I can't say about the authenticity of that cap photos, it's just one I found on the net.

    But there are lots of documented "fake" parts from Asia, whether just fake numbering (re-numbering?) or cloned semiconductors with very poor internals being sold as higher voltage/current/speed devices.

    I recently ordered samples of 35A and 50A bridge rectifiers from China. The samples arrived and were marked as such, but the black printed writing was the only difference between the 35A and 50A parts.

    I tested on a big DC PSU, and the forward voltage of the diodes was EXACTLY the same in both bridges, running at any current. I even ran the two bridges in series to match the same currents, and yep, both bridges diodes dropped the same Vf, down to the last mV.

    Even worse, I tested a good brand 25A bridge rectifier as well, it was the same! My conclusion was that the China bridge rectifiers were both just 25A parts, with "fake" part numbers printed on them. :(
     
  15. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    I wouldn't expect the voltage drops would change between a 35A and a 50A rectifiers. Was thinking the current rating was only an indication as to how much current it could "stand"....?
     
  16. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I've worked a bit with power diodes! These are not the first bridge rectifiers I have tested. Generally the higher amp rated parts have a slightly lower forward voltage, as the higher current diodes are larger.

    If the Vf curves of the two rectifiers are identical, it means the two devices will run at the same temperature rise at the same current. In that case, the only difference between a 35A and 50A part is the 50A part is rated to run a LOT hotter... And then why do you need a 35A version? ;)

    Same identical package, same physical appearance, identical Vf curves, just different writing printed on the packs.
     
  17. PackratKing

    Well-Known Member

    Jul 13, 2008
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    :eek: Good Grief..... Y'all gotta be kidding me... Tho' I am not really the least surprised someone would try and pull this BS
     
  18. ian field

    Distinguished Member

    Oct 27, 2012
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    The high ripple current reservoir electrolytics have riveted lugs just long enough to pass through the board with enough to solder, they're not intended to be cropped after assembly and are equal length - smaller wire ended electrolytics have short & long as someone already described.
     
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