Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

  4. Jan 14, 2015 #3

    berkeman

    User Avatar

    Staff: Mentor

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

    davenn

    User Avatar
    Science Advisor
    Gold Member

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar
    Science Advisor
    Gold Member

    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

    User Avatar
    Science Advisor
    Gold Member

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar
    Science Advisor

    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

    User Avatar
    Science Advisor
    Gold Member

    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
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Help me identify this capacitor
Loading...