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HOWTO Determine Unknown XTAL Freq

Discussion in 'Electronic Basics' started by, Apr 20, 2007.

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  1. Good day.

    I recently removed some crystals from some old electronic devices but do not
    know what frequency they are.

    Is there an easy and accurate way to determine their freqs?

    Thank you.

  2. Phil Allison

    Phil Allison Guest


    ** Try reading the labelling.

    Nearly all crystals are printed or stamped with their frequency in MHz.

    ........ Phil
  3. Radiosrfun

    Radiosrfun Guest

    What sort of equipment? That may tell us a lot. IF TVs for example, the
    Color Burst Crystals are one frequency. If from say computers - there are
    others used. Aside from that - they're usually stamped and if you can't make
    them out - then a crystal tester with associated readout device would help.
  4. jcomeau_ictx

    jcomeau_ictx Guest

    I'm assuming you don't have an oscilloscope? You might be able to use
    one at your local high school. If just hooking up the test leads
    doesn't start it oscillating, get it going with a 9V battery through
    some safe resistance, at least 10K probably.

    I don't know anything about your electronics background, but if it's
    an option, and you don't have access to a scope, you could build a
    simple circuit with a PIC microcontroller and hook the crystal to it;
    then program a delay loop and flash an LED with some fraction of the
    crystal frequency. I don't know offhand what would happen if the
    crystal frequency were too high for the uC though. Probably nothing
    destructive, but you wouldn't get the correct reading. I'd get my
    hands on a scope if I were going to do much messing with crystals
    anyway. I've seen them pretty cheap on eBay but of course the shipping
    charges will get you.
  5. John Fields

    John Fields Guest

  6. DaveM

    DaveM Guest


    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

    Life is like a roll of toilet paper; the closer to the end, the faster it goes.
  7. jasen

    jasen Guest

    a 4060 or two might be more convenient than a UC for this task.

  8. jcomeau_ictx

    jcomeau_ictx Guest

    It might, especially with a solderless breadboard. The basic idea is
    to make the invisible visible, and how you do it depends mostly on
    what you have available. My preference would be to use a
    microcontroller, since I'm more familiar with them, and changing the
    delay loop is just a matter of a few lines of assembly code rather
    than changing wiring. The last time I used a counter chip (a 4040) was
    13 years ago:

    What I don't know, not having a scope available, and never having
    played much if at all with crystals, if a scope probe will start a
    crystal oscillating by itself, or if a voltage needs to be applied
    across it. I just bought one on eBay so I guess I'll find out in a few
  9. Phil Allison

    Phil Allison Guest

    "jcomeau_ictx" <>

    ( snipe mindless drivel)

    ** **** OFF - Bloody Google IDIOT !!

    ........ Phil
  10. jcomeau_ictx

    jcomeau_ictx Guest

    Sounds like someone could use a beer.
  11. Phil Allison

    Phil Allison Guest

    "jcomeau_ictx" <

    ** **** OFF - Bloody Google IDIOT !!

    You are a KNOW NOTHING ASS dishing out STUPID and WRONG advice.


    You pathetic, asinine Frog

    ......... Phil
  12. Chuck

    Chuck Guest

    Yes. There are many easy and accurate
    ways to determine the frequency of a
    crystal. They require some test
    equipment though. Rather than have the
    group guess what you have and to what
    lengths you might be willing to go to
    determine the frequencies, why not give
    us some more information?

    I assume that if you had any of the
    equipment that would be needed, you
    would not be asking the question, and I
    strongly suspect that your curiosity
    about the crystal frequencies is not
    commensurate with the expenditure of
    time and money necessary to quench it.


  13. John Fields

    John Fields Guest

    What he's trying to tell you, in a nice way, is that it seems that
    you don't know what you're talking about.

    You see, there are two things you could be referring to: a crystal
    or a crystal oscillator.

    If it's the former, then before it can be made to oscillate it must
    be surrounded by circuitry which will force it to oscillate.
    Neither putting a scope probes across it nor placing a DC voltage
    across it will cause it to oscillate.

    If it's the latter, then it's a "crystal oscillator" not a "crystal"
    and it will contain the crystal and the circuitry needed to make the
    crystal oscillate when it is supplied with the proper supply
    voltage, not by putting a scope probe across it.

    Go here for a clue:
  14. jcomeau_ictx

    jcomeau_ictx Guest

    Thanks for the edification. I thought I made it clear that I was

    Different newsgroups have different cultures, and I'm not familiar
    with this one yet. comp.lang.forth, for example, usually makes a
    reasonable attempt to answer the OP's question before degenerating
    into ad hominem attacks and other vicious sniping. Live and learn.

    I still think the uC approach might work, but I have to dig up another
    crystal to make a quantitative comparison. I'll post when I have
    something concrete to offer.
  15. Phil Allison

    Phil Allison Guest

    "jcomeau_ictx" <
    ** Go shove your



    You pathetic, asinine Frog Fuckhead

    ......... Phil
  16. Phil Allison

    Phil Allison Guest


    ** Like reading the labelling on the damn things.

    Wake up - the OP was some kid trolling.

    ........ Phil
  17. Once again, Phyllis raises her ugly head and howls:

    Ignorant little Aussie bitch. Some crystals are marked with channel
    numbers, stock numbers, receive frequency where you don't know the
    offset for the IF, or even unmarked after the PC board is unwashed.
    Turn off the computer and take your hormones.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  18. Phil Allison

    Phil Allison Guest

    "Michael A. Terrell Psychotic Autistic FREAK"

    ** Up to the OP to post that sort of info.

    Since he has not come back, he is most likely a troll - or he read my
    post, opened his eyes & realised the frequency WAS written on the damn

    Either way -

    YOU can go a shove your pointy head up a dead donkey's backside where you
    normally hide it.

    **** BRAIN !!

    ........ Phil
  19. Thank Agent for killfiles....


  20. Phil Allison

    Phil Allison Guest

    "Peter A Fuckwit Forbes" <>

    ** ROTFL !!

    What a FUCKING MORON !!!

    ........ Phil
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