Help with 12v cfl driver!!

Discussion in 'General Electronics Chat' started by Clark44, Sep 1, 2014.

  1. Clark44

    Thread Starter New Member

    Aug 11, 2014
    15
    0
    Hello
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    I am trying to build this circuit, and there are some issues i am facing.
    I was able to make a working prototype on breadboard, but as i was getting happy and starting to make it permanent i thought i should check it again and then this thing happened. My transformer started giving strange noises and then cfl gone from bright to low and completely off and at the same time my transistor was burning damn hot. I had no idea why it happened? It was running great minutes ago and tested running it for 30 minutes and it was running fine and everything was cool, i have big heatsink installed on the transistor. Still when it was working during that 30 minutes, heatsink was safe to touch, but now it might even melt solder.

    I tried different transistor, capacitor, resistor but the transistor is still getting hot.

    Just to let to know, when i was packing it all up, i saw one of the high voltage wire was touching the heatsink of the transistor, do u think this has anything to do with this?

    Also i used D313 transistor.

    Regards!
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
    hi 44,
    Checking the d/s for the D313, it does not show the metal Tab of the transistor being connected to any other pin, its possible however that the very high voltage could have internal shorted from the Tab to another pin.???
    Have you tried changing the D313.?

    E
     
  3. Clark44

    Thread Starter New Member

    Aug 11, 2014
    15
    0
    Transistor is good, also tried using different ones as well but the problem is same, every transistor i connect is getting hot. Do u think i may have shorted the windings of the transformer?
    I also also tried TIP41C, still it is getting hot and not working.
     
    Last edited: Sep 2, 2014
  4. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
    hi,
    Do you have an oscilloscope to check if the circuit is oscillating correctly.?
    If you have wound your own transformer, its possible you have shorted turn.
    E
     
  5. Clark44

    Thread Starter New Member

    Aug 11, 2014
    15
    0
    I guess i have to rewind it again, this time i am gonna take its resistance reading. BTY I don't have oscilloscope.
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    783
    The Australian firm; Dick Smith Electronics used to do a shorted turns tester - the kit handbook and schematic have escaped onto the internet.

    Might give false positive on the primary winding for a low voltage blocking oscillator, but should give an accurate indication on a CFL tube driving secondary.
     
  7. Clark44

    Thread Starter New Member

    Aug 11, 2014
    15
    0
    Well, i rewinded the transformer, the third attempt, and it is working again. I guess in the end transformer was shorted due to HV secondary was touching transistor heatsink. This time i made sure that i there is proper insulation between every layer not just secondary. I am gonna put everything back together in pcb today. Breadboard testing was successful and cfl was able to light up about 60% bright. Gonna need a bigger heatsink though.
    Thanks for telling me about this short turns tester.
     
    Last edited: Sep 3, 2014
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