LED light board works sometimes

Discussion in 'General Electronics Chat' started by AlgoesSailing, Feb 27, 2016.

  1. AlgoesSailing

    Thread Starter New Member

    Feb 27, 2016
    I will attempt to be brief while proving the info that i have. I have two smoke/light machines that I use for my band: Chauvet Geyser RGB Jr. Recently the blue LEDs on one of the devices stopped working. Here is the board:


    I re-soldered the connections on the blue LEDs, plugged it back in and they worked a few times, but then stopped working again. I did a continuity test of all connections including pin connectors and the three silver dots on the board and compared them with the other board that I have: everything was identical. I then tested voltage at the pin connector:


    The voltages are as follows, with the board connected:
    On the "bad" board, between U and R is 7.3v, U-B is 10.1v and U-G (which is actually the blue LEDs) is 13.2
    On the "good" board, between U and R is 6.9v, U-B is 9.8v and U-G (blue LED) is 10.2
    I verified these voltages on the second machine and all voltages were within 0.1v of the above.
    Voltage without the board connected is approximately 12v at each pin.

    I assume that 7v is required for the red LEDs and the blue and green both require 10v. My first question is what would cause the voltage to be so much higher on the LED lights that do not light? Secondly, I would consider soldering wire to the lights instead of using the board but I do not know how to tell if they are in series or parallel, and how it might effect the other lights if I do so.

    Thanks for any help or info that you can offer
  2. ian field

    AAC Fanatic!

    Oct 27, 2012
    Those look like the same type of LEDs used in my bicycle light - sometimes they go intermittent.

    If they're in series, one going open circuit will kill the whole chain.

    The bicycle lights worked OK for a few months then started imitating Morse code as they warmed up - the cheap Chinese replacement LEDs have bee n OK.........so far.

    LED drivers should be constant current - the output voltage will rise with no load.
    #12 likes this.
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    I don't see how you get a 13.2V reading when, with the board disconnected, the maximum is 12V (presumably the power supply output voltage)?
  4. dl324

    AAC Fanatic!

    Mar 30, 2015
    Measure the voltage across each of the blue LEDs on the bad board.