Simple LCD Clock Circuit Help

Discussion in 'The Projects Forum' started by F27, May 28, 2011.

  1. F27

    Thread Starter New Member

    May 28, 2011
    2
    0
    I have one of those simple LCD bedside alarm clocks which has basic functions like time, date, alarm and a stopwatch. One day it was dead and putting in a new AAA didn't fix it.

    I opened it up and tested the x3 104 thermistors and x1 2.2K resistor with an Ohmmeter and found that 2 of the thermistors are not having current pass through them, could that be the issue as to why its not working?

    My knowledge of circuitry is only basic so I was wondering why there are even thermistors in this thing as it does not have a temperature function. How would a basic clock like this have just died and could it be something more serious like the chip failed?

    I have included pictures of the PCB and would really appreciate it if someone could tell me more about what I'm looking and and whats likely to be the problem. I've got a soldering iron and spares.

    Thanks for the help,

    [​IMG]

    [​IMG]
     
  2. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    Those are not thermistors. They are ceramic capacitors.
    "104" is indicative of a .1uF value.

    All the work is done in that "blob" on the left. It is a "blob I.C."

    The best you can do is check that power and ground paths
    are not physically broken. Look for broken traces on the circuit
    board, broken wires (internally or externally) etc..

    Also, as mentioned by another member earlier in another thread,
    it is amazing how much trouble shooting can be done by poking
    and tapping around with a stick.

    It was a slow night and I didn't like the misidentification of the components.
     
  3. F27

    Thread Starter New Member

    May 28, 2011
    2
    0
    I'm sorry but what's that supposed to mean? Not everyone knows this stuff.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Thermistors are specialty components, almost never used. What you call thermistors are capacitors, which are very common. They would also show as open to a meter, this is normal.
     
  5. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    Whoa buddy, I didn't mean to offend.

    What I meant was the main reason I posted was to try to
    help to correctly identify a component. As you may have noted
    by the rest of my post there is not much else I could say
    as these types of products are not usually (but sometimes
    you may get lucky) repairable.

    Sometimes statements in print don't come across as intended.

    My apologies.

    Anyway, if you have anymore questions don't be afraid to post
    you won't find a friendlier forum.
     
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