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Unknown capacitor.

Discussion in 'Datasheets, Manuals and Component Identification' started by Tha fios agaibh, Nov 9, 2018.

  1. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    That black thing U2 (3rd picture) is a photo switch that senses when the punch carriage returns. Its got a led on one side with a 3.3k limiting resistor, I don't know the specs, but perhaps we can figure out the ps/zener voltage based on that sensor.

    Alas, I've got other projects to tackle this weekend so I may not respond for a while.

    Thanks (as always) for everyones input.
     
  2. kellys_eye

    kellys_eye

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    Looks to me like the capacitor reads μ68 I 250 F1 (could be 350, not 250) - either way the 250/350 is the voltage rating.

    I would assume your local supply is 120V with a 250V rated capacitor - seems a bit close to the knuckle for a 240V AC mains......
     
  3. davenn

    davenn Moderator

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    Sep 5, 2009

    where did you get that from ? .....
    652 is 6.5nF 654 would be 650nF = 0.65uF


    naaaa ... that's looks more like a N60 or W60


    @Tha fios agaibh you have 3 photos of the cap ALL of them are blurry

    PLEASE provide a sharp easy to read pic of the text on the cap
     
    Last edited: Nov 10, 2018
  4. Bluejets

    Bluejets

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    Oct 5, 2014
    Ones on 220v here are 330nf 400v.
    if you're on 110 then maybe 200-250v like others have said.
     
  5. kellys_eye

    kellys_eye

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    Another look at it and I'm convinced it's what I say except the 'I' is actually a 'J' (tolerance code).

    There's no way you can drop AC mains to anything 'comfortable' without a capacitor in the 100's nF range. Besides, I've never seen a (relatively) low volage capacitor of that type, in that value, or in a package that's that large......

    It's 680nF and the meter test proves it!
     
    Last edited: Nov 10, 2018
  6. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Sorry, I couldn't upload full resolution because of file size but it definitely says 652. The photo was the best I could get of the little guy @ 1mb.
    Perhaps this is not a 3 digit code like found on smaller ceramic caps?

    Yes, bottom line looks like W60 250
     
  7. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    I'd think it'd be way over the knuckle for 240v mains considering 339v peak.
    The 250v rating may even be a bit close with our 170v peak.

    I'd take another picture of the cap but unfortunately it's across town.
     
  8. davenn

    davenn Moderator

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    Sep 5, 2009

    Thanks for the confirmation, mate ..... not sure why the meter reading isn't anywhere near the printed value ??

    3 digit codes are used on any value these days


    it wasn't a full resolution problem ... it was a focussing problem ..... none of the cap photos were focussed ;)




    well the code doesn't match then as the 652 code IS confirmed .... yet as I stated above, the value doesn't match the reading ????

    maybe that's why it has failed because the manuf. used the wrong value ???




    Dave
     
  9. kellys_eye

    kellys_eye

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    Capacitor.png
    You're reading the wrong line.

    1. there is no standard value of 6.5nf
    2. I read the SECOND line as "U68 (0.68μF), J (5% tolerance) and 250 (250V)" although the 250 could be 350??? F1 is something I haven't decoded yet (probably its 'class').
    3. The meter reading shows 680nF (which is 0.68μF) which, strangely enough, equates with my proposal. Capacitors rarely fail to exactly the marked value......
    4. the 'J' is the international capacitor code for 5% tolerance.
    5. the reactance of a capacitor of 6.5nF at 50Hz is some 500kΩ - clearly ridiculous in that application. At 680nF (and 50Hz) the reactance is 4.7kΩ - clearly within a range of intended use.



    What more information do I need to prove?
     
    Last edited: Nov 10, 2018
    Tha fios agaibh likes this.
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Nothing. I'm convinced that the zener diode is shorted and should be replaced with one of the same voltage but higher wattage rating. After replacing the zener diode, make sure the diode bridge is actually working. There may be one or more diodes open or shorted in the bridge rectifier. Surely @Tha fios agaibh knows how to troubleshoot and fix this.
     
    Tha fios agaibh likes this.
  11. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    The bridge checked out ok with my dvm. The challenge is figuring out what the zener value should be. I'm guessing its a 5.1v

    Good catch kellys_eye, I thought second line said w60 but it could be u68. (My eyes aren't what they used to be)
    It certainly make more sense than a cap failing to a higher standard value.
     
  12. davenn

    davenn Moderator

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    you need to prove lots ;)

    well the OP has already said it ISNT u68 he said it is W60 and 250 as I have already suggested !!
     
  13. Tha fios agaibh

    Tha fios agaibh

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    Right, at least that's what I tough it said.
    I could be wrong.
    I will put it under serious magnification when I get back Monday and take a better picture.

    What kind of current should we be looking at here ahead of the bridge?

    If it was a .0065uf (652 on first line) Xc @60 hz would be 408k and with the 1meg parallel resistor give a combined resistance of about 290k putting current in the range of about .4 to .6ma.

    But if it was .68 as meter shows (w60 actually says u68) Xc @60hz would be 3.9k and put current in a healthier range of about 31 to 43ma.

    Let me know if my math is off, but this 680nf reading seems right where is should be regardless of how its marked.
     
  14. Bluejets

    Bluejets

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    Oct 5, 2014

    Attached Files:

    Tha fios agaibh likes this.
  15. davenn

    davenn Moderator

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    OKKKKKKKKKKK :)

    now that that is finally cleared up, we will move on ;) :)

    it's all in getting the details correct, else it causes all sorts of arguments
     
    Tha fios agaibh likes this.
  16. Tha fios agaibh

    Tha fios agaibh

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    ....well, I did preface the sentence with "if".
     
  17. hevans1944

    hevans1944 Hop - AC8NS

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    Magnification was fine. The picture was out of focus in the lettering plane of the capacitor. Note that everything else in the image is sharp and clear, thanks to the auto-focus POS software your camera uses.

    Here is a better idea: get a largeish sheet of white paper and cut out a rectangular hole in the center for the capacitor to just "peek" through. Photograph the lettering on the capacitor against this white, featureless, background to foil the auto-focus mechanism in whatever camera you are using. One megapixel resolution should be just fine.
     
  18. Tha fios agaibh

    Tha fios agaibh

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    Good idea I'll try that if it won't focus on lettering. I get the idea POS means something other than what I'm thinking.;)

    Meanwhile, I came across the same value film cap in my shop that I've used in similar applications. My camera performed well in capturing this one. The same manufacture but markings are different. 20181111_142609-1.jpg
     
    hevans1944 likes this.
  19. hevans1944

    hevans1944 Hop - AC8NS

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    Is there any correlation between the value measured for this capacitor and the markings printed on it?
     
  20. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    I don't understand the codes other than u68 for .68uf, 305v rating, and its a type X2 film cap which I understand to be more robust and less likely to explode at end of life.

    What I'm now trying to figure out is how to determine the zener value in the ps. There's a optointerrupter that has a 3.3k inline with the diode which leads me to believe the voltage is much higher than I first thought. I'll have to look up specs for the o-i to see if I can narrow down where the voltage should be. Suggestions?
     
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