How common is this? ir emitter problem

Discussion in 'General Electronics Chat' started by inwo, Nov 16, 2013.

  1. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
    Wife picked up a converter box at a garage sale for an old tv in the bsmt.

    All packed up and looked new. Had are locals scanned in so it did work once.

    Remote didn't work. She's very knowledgeable about tv hook-ups and remote programming.

    She was testing batteries and hinting for ideas.

    Told her that I have an ir receiver that I use with the scope.
    No output!
    Battery and connections good.
    Another remote proved my receiver.

    Inside shows power to ir emitter.
    Keypress shows upkick in current.
    Emitter test ok forward voltage-wise.
    Scope shows data. No ir output however!

    Told her to get a donor remote for transplant.
    Put one in from a 30 year old rca remote and it works fine.

    What I'm wondering is what kind of failure makes an ir emitter stop emitting ir?

    Wasn't connections as I tried it again after removal.
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Over current is a big killer if IR emitters.

    On a used box, you just never know what it was subjected to. Someone cod have tried connecting a 9 volt because it was the only battery in the house. It could have been weak from the factory and only lasted long enough to program the box.
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    My guess, given the nature of where these remote is commonly used.... it got dropped to the floor one time too many.
  4. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
    I'm under the impression that it's basically a diode.

    It still acts like a diode. Forward and reverse V drop.

    But doesn't emit. :confused:
  5. tshuck

    Well-Known Member

    Oct 18, 2012
    How is this verified?

    A way to see if it is working is to hold a camera up to face the LED and mash some buttons on the remote. The camera can detect IR where you cannot.
  6. bertus


    Apr 5, 2008

    How did you check that the IR led is not emitting anymore?
    You could have a look with a digital camera (like in a cell phone).
    If the led is emitting, you should see a bright spot when activated.

    Last edited: Nov 17, 2013
  7. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
    I built my tester before the digital world, but it hasn't failed me yet.

    I'll have to see if the emitter is still around.

    I have a photo transistor connected to appropriate biasing, a 9v battery, and scope probe.

    I check it each time with a known good remote.

    Think it's from rs 30 years ago. Has always responded to any ir source.