Small Fixed Inductor Unavailable?

Discussion in 'General Electronics Chat' started by Lonelynewyorker, Oct 4, 2014.

  1. Lonelynewyorker

    Thread Starter New Member

    Aug 29, 2014
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    Hello. I was doing some repairs, when i seem to have found the culprit. It is labeled L3 so assume this is an inductor. This circuit board is from the late 80s. Does anyone have any advice for replacing this inductor that has failed. thanks.

    Have I identified it improperly? Thanks again for your help.
     
  2. b1u3sf4n09

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    May 23, 2014
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  3. Lonelynewyorker

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    Aug 29, 2014
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  4. Lonelynewyorker

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    Aug 29, 2014
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    but even at 8.7 mh, i was still not able to find this part online. if you have time and patience could you provide me a link to a suitable part i could put in? sorry im very unfamiliar with inductors.
     
  5. b1u3sf4n09

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    May 23, 2014
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    Seems like that is not an easy value to find. I'm not sure what circuit this is going in to, but based on the fact it's a 5% inductor means it probably will work with a close value. You may try a 8.2 mH inductor:

    http://www.digikey.com/product-detail/en/78F8R2J-RC/M10146-ND/1306004

    What is the circuit in question? Do you have a schematic?
     
  6. b1u3sf4n09

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    May 23, 2014
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  7. takao21203

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    Apr 28, 2012
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    you could use 8.2mH but I'd say 4.7mH.

    If you'd present the circuit, we could figure out if the exact value is important or if just any larger value will do.

    8700uH isnt common at all again need to see the circuit to decide if a different value could do damage.
    How do you know its broken did you measure it?
     
  8. #12

    Expert

    Nov 30, 2010
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    No luck! I read that as 8700 somethings. Can you measure its ohms?
     
  9. Lonelynewyorker

    Thread Starter New Member

    Aug 29, 2014
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    actually the inductor was blown up and in two pieces. it was unreadable. a friend of mine, happened to have the same keyboard so he sent me a picture of the burned and broken part. here are the photos you requested. thanks again everyone
     
  10. Lonelynewyorker

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    Aug 29, 2014
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    it was leading into a chip that i researched to be a "floppy disk controller" which explains why i was getting floppy disk errors.
    if you look its the peice removed marked L1. THANKS ALOT!
     
  11. Lonelynewyorker

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    Aug 29, 2014
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  12. takao21203

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    yes it is a UPD72069 FDC.
    Pin 16 is Nc interestingly: file:///C:/Users/Max/Downloads/upd72069gf3ba.pdf
    http://doc.chipfind.ru/pdf/nec/upd72069gf3ba.pdf

    I'd like to ask you to test pin16 where it is connected- a ground line perhaps?
    And where does the other end of the coil go? To the floppy drive?

    chances are if it has just burned out, something else is damaged too.
    I'd really just try 8200uH or 4700uH, guess maybe it is used as a filter coil.
    RF inductors with 8200uH have a fairly high Dc resistance actually.

    I have small 8200uH Panasonic potcores here (DCR is 22 Ohms I think), costed less than $1, maybe in the US you can get the part faster from a distributor. With a DMM you could check where the coil connects to.
     
  13. Lonelynewyorker

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    Aug 29, 2014
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    pin 16 is NC NO CONNECTION
     
  14. takao21203

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    then maybe by the means of a parallel antimatter universe, the board has said Arrivederci.

    synchronuosly, all the units have changed their appearance so this coil goes to nowhere and it cant be repaired.

    Seriously, did you test the pin hole against some common signal lines? with a continuity tester?
    If no result, then well, something serious happened in the parallel universe.
     
  15. Lonelynewyorker

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    Aug 29, 2014
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  16. takao21203

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    OK thanks. Do you have a DMM and do you know what is continuity tester and do you understand most electrolytics just connect to ground and did you trace the other end (guess goes to the floppy drive)?

    If it doesnt go to ground just tap everywhere until you find it.
     
  17. Lonelynewyorker

    Thread Starter New Member

    Aug 29, 2014
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    hey if you have some information pertaining to fixing this inductor, please let me know. im not really interested in answers
    from the rest of the people commenting here.
     
  18. wayneh

    Expert

    Sep 9, 2010
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    How is everyone getting to 8 for the first band? It looks bluish maybe, and maybe grey. It's hard to tell since most of the band has been worn or burnt off. A photo or inspection from another angle might resolve what color it really is.
     
  19. Lonelynewyorker

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    Aug 29, 2014
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    its DEFINITELY GREY.
     
  20. #12

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    Nov 30, 2010
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    Well...gray is 8...isn't it?

    87 isn't a, "standard" value. Neither is 97. Whole lotta guessing going on here. :oops:
     
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