Please ID This Component: Crystal Oscillator

Discussion in 'General Electronics Chat' started by Manbearpig, Feb 27, 2015.

  1. Manbearpig

    Thread Starter New Member

    Oct 30, 2014
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    I'm trying to fix a remote transmitter and think this may be the culprit; it rattles when shaken. The remote was dropped shortly before I noticed it stopped working, so that's my best guess. I fixed the remote one other time when the antenna broke off at the solder pad, and the solder joints for the crystal were broken. I've been soldering and tinkering for a long time but never worked with crystals. It looks like this one could be a 49U or UM-1 package. I searched DigiKey for a 27.147MHz crystal but couldn't find anything. How critical is it that the MHz match exactly? Do any of you have one of these you could sell? Any help is appreciated!
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    This is a plain crystal, not a complete oscillator, and the exact frequency is important. While lots of "standard" frequencies are available through distributors, non-standard parts like this one are very common in volume applications. ebay?

    ak
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is a common xtal used in RC toys etc, you may be able to scrounge one off of a dud Txmtr.
    Max.
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    or try International Crystal, in Oklahoma City. 27.145 is one of those rc chanels between the cb channels, so isnt as plentifull as the cb crystals.
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Doubt its the Xtal,try resoldering it back on.
     
  6. bertus

    Administrator

    Apr 5, 2008
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  7. Manbearpig

    Thread Starter New Member

    Oct 30, 2014
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    I reinstalled the xtal and it still doesn't work. Here's the rest of the circuit in case you think it might be something else

    xtal1.jpg xtal2.jpg
     
  8. flat5

    Active Member

    Nov 13, 2008
    403
    17
    "it rattles when shaken"
    Replace it or make a little xtal checker. (Google)
    In your second photo there is a solder blob you should remove.
    It is where you soldered the xtal.
    xtal checker1.png
    xtal checker2.png

    BTW, I have found that if you place a cap in series with the hot lead going to the xtal you can often test parallel coil/cap combinations for approximate frequency.
    You do need a scope or freq. counter or radio.
     
  9. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Any Citizens Band x-tal ch. 1..40 will be less than 1% off and as such, will have next to no impact on range in an IR remote control transmitter.
     
  10. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
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    Since it rattles it is probably bad, so why not open it up? Do you have a Dremel tool and a cut off wheel? It may just be a broken connection that is fixable.
     
    Lundwall_Paul likes this.
  11. Manbearpig

    Thread Starter New Member

    Oct 30, 2014
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    I contacted International Crystal MFG and they asked if I knew the load capacitance or had the schematic. Since I knew/had neither, they had an engineer look at the circuit pictures and their best guess would be 20pf. Then I would need to decide on whether it is fundamental or 3OT; any ideas?

    I'll dremel mine open when I get some time
     
  12. Lundwall_Paul

    Member

    Oct 18, 2011
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  13. Manbearpig

    Thread Starter New Member

    Oct 30, 2014
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    0
    Yup, it's broken. I can't find any exact matches, the closest is 27.145. ICM could make one but it's pricy and may not be the correct load capacitance. Looks like I should just buy a new remote. Thanks for the help!

    crystal.jpg
     
  14. ian field

    Distinguished Member

    Oct 27, 2012
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    Admittedly rare - but they do sometimes fail.

    There's various crystal checker schematics floating about the web - usually one or 2 transistors and a small handful of resistors, capacitors etc.
     
  15. ian field

    Distinguished Member

    Oct 27, 2012
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    Loading capacitors could be your salvation - if a standard crystal is cheap enough, try pulling its frequency by using 1 or 2 preferred values lower loading caps.
     
  16. flat5

    Active Member

    Nov 13, 2008
    403
    17
    Try super glue.
     
  17. MrChips

    Moderator

    Oct 2, 2009
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    April 1st is over.
     
  18. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The crystal is broken.
    There is no way of mending it.
    The superglue will not work, as the resonance is dependend on the size and thickness of the crystal.

    Bertus
     
  19. ian field

    Distinguished Member

    Oct 27, 2012
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    There was a documentary about early home computers, there were several firms that offered their computers in kit form.

    One recounted an occasion of a kit returned under warrantly to find out why it didn't work - it had been assembled perfectly, neatly and accurately - with polystyrene cement instead of solder!
     
  20. MrChips

    Moderator

    Oct 2, 2009
    12,442
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    That's a new one. Should go in the "Soldering for Dummies" instruction book.
     
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