High esr

Discussion in 'General Electronics Chat' started by inwo, Feb 14, 2014.

  1. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    Are these caps bad?

    I don't want to disturb them unnecessarily.

    150 uf 450 volt

    Both read about 7ohms esr.

    To tell the truth I've never found in circuit esr readings useful.

    I just don't have the experience.
    Not that I haven't replaced hundreds. Just haven't found a relationship between bad esr and good esr.

    My chart only goes to 250v and 100 or 220uf which lists as .5 to 1 ohm.

    I'll google while I wait.

    Blown main fuse.
     
  2. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    All the replacements are listed as 1.2 or less.

    Anything "in circuit" will read lower. Correct?

    These are $7 each and I don't have any here.
    I'm quite sure I'll damage them with removal. Leads go thru grommets.

    Just need another opinion as this will be the first time esr meter has been helpful.:eek:
     
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
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    7 ohms seems really high, even for a bad one. It would be nice to measure a new one just to confirm your meter.
     
  4. #12

    Expert

    Nov 30, 2010
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    I agree. No direct knowledge of this situation, but I estimate that 7 ohms is excessive.

    Xc @ 120 Hz calculates to 8.84 ohms. ESR nearly as high as Xc seems unacceptable.
     
  5. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    Thanks, seems obvious.

    Was just wondering if there are some circuit situations that would cause high reading.

    None that I know of.

    I'll pull em.

    Bridge checks ok.
     
  6. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    Just hit me now.

    Pretty high voltage rating for a tv. No wonder I don't have any in stock.:confused:

    Or to compare.
     
  7. #12

    Expert

    Nov 30, 2010
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    The only thing I have in that range is a metal can about 2&3/4 inches long by 1.4 inches diameter.

    "Seems obvious" right after you play with the math a bit.;)
    I recommend you make a habit of doing that. It's kind of like running a simulation, but faster, and you don't have to learn SPICE.:p
     
  8. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    Out of circuit its worse. One is up to 13 ohms and they read 50uf.

    Digikey was down this afternoon anyway.

    I see some other things in my cart.

    I'll order tomorrow.

    I always order double of everything. No wonder the place looks like it does.:D

    I've changed lots of power supply caps. Can't find any over 250 volts Though. Most designers must cut it pretty close.

    This is an LG that I repair every 6 months.
     
  9. #12

    Expert

    Nov 30, 2010
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  10. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    Digikey has them for less but 3000hr versus 10,000 hr.

    Who would by a tv if they knew it had 3,000hr caps?:D
     
  11. #12

    Expert

    Nov 30, 2010
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    What percentage of the population even knows what a capacitor is?:rolleyes:
     
  12. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    Guarantees some failures in 10 months.:eek:
     
  13. rc3po

    Member

    Feb 12, 2014
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    ....job security.lol
     
  14. #12

    Expert

    Nov 30, 2010
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    Aha! That explains why I have so little business after all these years of quickly delivering high quality results at low prices. I should have been constantly working to reduce the mean time between failures. :rolleyes:
     
  15. takao21203

    Distinguished Member

    Apr 28, 2012
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    most people believe, if you connect too many plugs to a single socket with expanders, it will overload the power line.

    Also the tangled mess of cables somehow could cause a spark and that in turn would immediately cause a fire.

    switching on/off a flourescent fixture consumes as much energy as it would require for a whole day + is reducing the lifetime significantly as well.

    Cardboard in a microwave will cause it to break.

    Unplug televisions in the night to save on electricity bill + best is to unplug all appliances.

    Most notorious, keep remote controls inside wrapping + never ever removed the foil from displays.
     
  16. snav

    Active Member

    Aug 1, 2011
    100
    10
    Those caps are too small for that rating. If it was my set I'd put a pair of 300@250v in series in place of each. Works like a charm for my KT88 PP monoblock to replace the original equip Sprague multisection caps.
     
  17. #12

    Expert

    Nov 30, 2010
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    Which caps?
    Did you just notice that I linked to 120 uf caps when I should have linked to 150 uf caps?
     
  18. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
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    May have meant, the originals.

    Too late now. They're ordered.

    Now that he mentioned it. I could have searched for physically larger (longer) caps of same value.:eek:
     
  19. alfacliff

    Well-Known Member

    Dec 13, 2013
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    cap is supposed to be 150 mfd and reads 50? get another one, that one is on its way out. high esr affects higher frequencies more than linear supplies. the esr makes the cap act likt lower capacitance due to rc effects. also, the esr makes it heat more and that kills the caps fast.
     
  20. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,884
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    Well in the 60s and 70s most did, When I would repair a TV, I was often asked if it was the picture tube or "the condenser".
    ;)
     
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