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Help me identify this capacitor

  1. Jan 14, 2015 #1
    Hello everyone!

    I need help identifying a capacitor. It reads 12.C29 Its very small, maybe .25" long.
    It's on an audio input board from my Kenwood A/V receiver.


    Thanks for the help!
    Josh
     

    Attached Files:

  2. jcsd
  3. Jan 14, 2015 #2

    Bystander

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  4. Jan 14, 2015 #3

    berkeman

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    Looks more like a cylindrical package crystal from that angle...
     
  5. Jan 14, 2015 #4

    davenn

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    Totally agree Mike. definitely, no doubts, a crystal OP reread it ... its 12.2x29 the x may be a 0 (zero)
    12.2 MHz or possible 12.2 kHz

    to the OP
    I can see a Hz printed on the PCB just to the right of that brown electro capacitor what comes before that ( hidden from view by the cap) ??

    Dave
     
  6. Jan 14, 2015 #5
    WOW - You guys are good.

    Dave - It says 12.288MHz

    Any Idea on where I can a replacement?

    EDIT - Just found a pack of 10 on Ebay for a few dollars.. worried about quality though.
     
  7. Jan 14, 2015 #6

    berkeman

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    Check Digikey and use their part sorting feature to look for cylindrical crystals.

    Although, as long as it fits in that area of the PCB, you could use a traditionally packaged crystal instead (still through-hole leads).
     
  8. Jan 14, 2015 #7

    berkeman

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    BTW, those two numbers are far enough apart that using the wrong frequency could affect circuit operation, especially in a radio receiver. I'd go with the frequency on the part. Do you have any idea why the frequency on the part differs from the silkscreen number on the PCB?
     
  9. Jan 14, 2015 #8

    Maybe they rounded the .288 to .29?
     
  10. Jan 14, 2015 #9

    davenn

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    its most likely to be the clock oscillator crystal for that large micro chip to the right of the crystal
    I would hesitantly guess ( in this situation) that several 10's of kHz probably wont make too much difference


    Dave
     
  11. Jan 14, 2015 #10

    How can I find its load capacitance? I'm guessing 16pf.

    You've all been very helpful, I thank you!
     
  12. Jan 14, 2015 #11

    davenn

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    you would need the service manual or detailed schematic of that part of the board
    parts list and/or schematic would have that info
     
  13. Jan 14, 2015 #12

    berkeman

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    That's a good ballpark guess for the crystal spec -- at that frequency 16-18pF is very common. Can you see any explicit caps on the PCB on the crystal nets? The total capacitance seen by the crystal oscillator circuit would be the two PCB caps in series (so half of their value) in parallel with whatever the input capacitance of the oscillator is.
     
  14. Jan 16, 2015 #13
    I really cant tell what the caps are - Im still very new to circuitry.

    What would happen if I placed an incorrect crystal on this board?
     
  15. Jan 16, 2015 #14

    berkeman

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    Hard to tell. What is the microcontroller (uC) chip to the right? Can you read a part number off of it? If so, the datasheet for that part may specify a particular crystal capacitance value, and recommend the corresponding PCB capacitors to get to that overall parallel resonant capacitance value.
     
  16. Jan 16, 2015 #15
    Well, the two caps next to the crystal say 10v100uf - as for the chip "Analog Devices ADSST-MEL322 173068.1-0.2 0240"
     
  17. Jan 16, 2015 #16

    berkeman

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    No, those are big electrolytic capacitors for the voltage rails. The caps I'm referring to would be small SMT capacitors, one from each leg of the crystal to ground.
     
  18. Jan 16, 2015 #17
    The SMT's are so small, there is nothing printed. I tried to get a picture, but my phone has no macro setting so close up photos are blurry. I'm going to hunt for the manual, but I doubt I'll find it.
     
  19. Jan 16, 2015 #18

    berkeman

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    You would need an LCR tester, or a "capacitance" test range on your DMM to measure the caps. They would likely be in the 30pF range.

    Just start with 18pF or so for the first crystals you buy. That should be pretty close.
     
  20. Jan 16, 2015 #19

    Baluncore

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    Why fix the crystal if it ain't broke? The brown stuff looks like glue to hold it in place.
     
  21. Jan 17, 2015 #20

    davenn

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    well he thought it was a capacitor initially

    but it still begs the Q you asked .....

    JoshB ... why do you want to replace the crystal ? it doesn't look damaged
    This thread so so far offtrack because of things not being established in the original post

    I think you need to start over and tell us all why you are delving into this receiver audio board unit and what is its fault / symptoms ?

    Dave
     
  22. Jan 17, 2015 #21
    OK - I thought it was damaged and the brown stuff looks to be coming out of the crystal which I thought was a cap. (I'm very new to circuitry and components)

    So I've had this A/V receiver (VR-7070) for many years - then suddenly a very loud high pitched whine would come from all speakers. So I assumed it blew a cap somewhere. When I dug into it, this crystal is all I could find with visible damage ( or so I thought).

    You guys really know your stuff - and I appreciate your help.

    Anyone know what I should look for? Or how I should approach fixing this?

    Josh
     
  23. Jan 18, 2015 #22

    Wes Tausend

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    Josh,

    The high pitched whine usually means some sort of feed-back has developed. The most likely cause will be a electrolytic capacitor to ground, that has failed, and now does not decouple a hf audio ac signal (aka feed-back whine) on a dc feed-back bias voltage line. The good news is the circuit is obviously still ampilfying, although strong feed-back can soon overheat delicate parts.

    It really would help to come up with a schematic since they often show a common feed-back circuit derived from the heavy duty output stages. But finding the factory pin read-out and specs, from the IC audio pre-amp chip may be just as good. Look for a pin that requires dc bias voltage and then replace the electrolytic capacitor that is supposed to decouple hf audio. Electrolytic caps are the most likely failure of aging equipment, so you were likely on the right logic track and do suffer from parts non-recognition just like you also suspected. The electrolytics are in cans, and have a plastic sleeve over them. I can see two with black plastic sleeves near the bottom of your photo for instance. The light stripe usually designates the voltage polarity. They are usuallly large enough that the volt and capacitance ratings can be easily read to facilitate replacement. Sometimes the sleeve is blue instead of black.

    If you are ambitious, you could replace all the electrolytic caps on the board with new, or known good used items.

    Wes
    ...
     
  24. Jan 18, 2015 #23

    sophiecentaur

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    And you wouldn't have the wherewithall to test it in any case. It will measure as an open circuit / very small capacitor. I guess if it had the damp in it, you may measure some conductance.
    PS did you ever see a 12kHz crystal? Here's one. This eBay link may not last long. :)
     
  25. Jan 19, 2015 #24
    Hey guys - I've managed to find the service manual, but if I could read it as intended I would be in a higher pay bracket....

    Manual

    If it helps, all I hear is the feedback - not the audio source. And would a bad cap show signs of damage in this case?
    Too bad i'm in school for Mechanical engineering and not electrical....

    Thanks again guys - this is a great forum!

    Josh
     
  26. Jan 19, 2015 #25

    davenn

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    Hi Josh

    unfortunately I don't really want to signup to a site just to download the file so I can read it
    I suspect others will probably feel the same way

    wonder if you can pick another site, thanks ? :)
     
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