Capacitor Noobery

Discussion in 'The Projects Forum' started by Videodrome, Nov 12, 2009.

  1. Videodrome

    Thread Starter Member

    Nov 12, 2009
    63
    0
    Hello. I am in my building infancy as im getting into electronics building and have a question as i need to buy some replacement parts for a circuit i am trying to replicate. the circuit has ceramic and film capacitors that i am not able to measure as i cannot remove them but they seem to have numbers printed on them and i was wondering if it is possible to identify their values this way? some of them have underlined and black tips. here is a photo of the circuit in question and the ceramic and filter caps labeled along with the numbers printed amongst them. thanks for the help


    [​IMG]
     
  2. Duane P Wetick

    Active Member

    Apr 23, 2009
    408
    19
    The 47n might be 47 x 10-9th. farads or .047 microfarads, a common value cap. The 47 unit(s) might be 47 picofarads (10-12). 10 might be 10pf. You can glean some values just by looking at the relative sizes; small size= small value.

    Have fun, DPW
     
  3. Videodrome

    Thread Starter Member

    Nov 12, 2009
    63
    0
    thanks a ton duane, that really helps. i managed to find out the printing on the unidentified capacitor that is sitting right under the smaller IC in the photo above. it has the number '101' printed upon it, here is a photo of it marked by a pink circle. it is quite small and it doesnt look like to be a disc cap, it resembles more of a droand im curious if i am in fact reading it right and if the marking of 101 makes sense to its small size. here is also a photo of the other ceramic disc capacitors that i was questioning about. note how some have black tips, does that have any significance?

    [​IMG]
    [​IMG]
     
  4. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    The circled cap looks like it may be an epoxy encapsulated ceramic cap. 101 could be 10 + 1 zero = 100pF but I wouldn't bet a body part on it. I can't see it very well so it may even be a tantalum cap. If so, 10uF would be common for that type of cap.

    As far as the black tips on the ceramic disk are concerned... dunno. I've seen thousands of caps marked like that and never gave it a second thought. Good question.
     
  5. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    It just hit me! I think that's a Silver Mica cap. So that would probably be 100pF
     
  6. k7elp60

    Senior Member

    Nov 4, 2008
    478
    69
    The capacitor marked 10 with a black band at the top is a 10pf with a temperture coefficent of NP0. NPO basically means with termperature variations the capacitance doesn't vary. All capacitors except those that are NPO will vary in capacitance depending on temperature and their individual specifications.
     
  7. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Ya learn something every day. I've been using NPOs for years but I've never made the connection of the black top, as NPO's are usually marked NPO. If you look at the padding cap in a xtl osc it will invariably be an NPO.
     
  8. Videodrome

    Thread Starter Member

    Nov 12, 2009
    63
    0
    hey thanks again you guys, i really appreciate it! :>
     
  9. Videodrome

    Thread Starter Member

    Nov 12, 2009
    63
    0
    hey again folks. so i went to my electronics store and got the ceramic caps that i needed but they did not stock any of the ceramic caps i needed with the black tips on them(NPO
    's). would it be okay for me to use a ceramic cap without a black tip(npo) in a place where one is supposed to be used?
     
  10. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    As stated earlier, NPOs are used where temperature stability is important. Did you look on Digikey?

    Edit: What makes you think the originals are bad? Ceramic caps have quite good longevity.
     
  11. Videodrome

    Thread Starter Member

    Nov 12, 2009
    63
    0
    i just made a look over at digikey and it seems they have what im looking for, but i also discovered that theres an electronics surplus store just a few blocks away from my home so ill see if i can pick up some tomorrow.

    most of my thinking is out of noobery as im still trying to find my footing, still learning. thanks alot cdrive!
     
  12. peranders

    Well-Known Member

    May 21, 2007
    87
    0
  13. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Well, it's not like you can see a whole lot of that cap in the photo!
     
Loading...