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need help with flyback transformer

Discussion in 'Repairing Electronics' started by lev77, Feb 15, 2011.

  1. tvtech

    tvtech Well-Known Member Most Helpful Member

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    24KV from a CRT Line Output Transformer makes a nice long blue 10CM arc when near to earth when running.

    Beautiful to see but bad to feel. Very bad.
     
  2. BrownOut

    BrownOut Banned

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    Why not use one of the many 555 circuits available for driving the coil? I've made a few, but they need a little more DC line protection from transients than are usually published. I expect the same would be true for lamp dimmers too. A handful of TVS diodes or transorbs and/or a RC filter should do the trick.
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Bit damp there is it? :D

    It's always said that it takes about 10KV per cm to arc in dry air.
     
  4. dave

    Dave New Member

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  5. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Yeah, that's exactly how I estimate the voltage outputs from my transformers. I think I read somewhere that it's actually more like 1.1Kv/mm, so that would mean 11Kv/cm (in dry air, at sea level, and a whole bunch more ideal situations ;) )
     
  6. tvtech

    tvtech Well-Known Member Most Helpful Member

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    No Nigel.

    Dry here. I simply take the Anode Cap off and hold it within 10CM of earth. Nice blue arc.
    You are welcome to visit and experience it for yourself :p

    Cheers
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I can remember seeing EHT 'meters' for measuring EHT on TV's, you adjusted a sparkgap until it just started to arc across, and read the voltage off a calibrated scale :D

    Bit crude and nasty, but probably all you really needed for testing EHT - generally if there was a low EHT fault it would be a LOT lower than it should be.
     
  8. BrownOut

    BrownOut Banned

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    I've done that experiment. It is pretty amazing how long of an arc can be drawn.
     
  9. unclejed613

    unclejed613 Well-Known Member

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    i once worked on a TV where the HV regulator transistor was shorted..... the arc came from under the anode cup and across to a piece of chassis that was 6" away.... humid environment of course... sounded like a cap gun going off.....

    i also drove an ignition coil from the output of an amplifier once. a crude ionophone.... you could hear the music from the arc
     
    Last edited: Mar 6, 2011
  10. ben7

    ben7 Member

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    With that high voltage and that size of a capacitor you are likely to be able to vaporize a small screwdriver with that! :O

    I stick with the caps from psu's that are rated at around 200V and anywhere from 33 to 1000uF.
    A nice bank of them charged up then shorted out makes a BIG bang, maybe you would want to use earplugs when discharging that big one! lolz

    -Ben
     
  11. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    For that matter, why not just use an old disposable camera? The flash capacitor is usually rated 330v, 120uF and can make a heck of a bang. Plus, it's already got the charging circuit in it :D On top of that, one of these caps discharging through your body probably won't kill you ;)
    Der Strom
     
  12. ben7

    ben7 Member

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    Are you sure about that?
    I'd think it would at least vaporize a nice hole in your skin and mess up your nerves!
    They way I charge them is with rectified 120V using two back to back 120V-9V transformers.

    However the flash caps are meant for quick pulse discharges, but the other ones I use aren't. I haven't had one fail yet but they are from good mfgs like NCC and Nichicon. I had some "OST" ones before but they spewed goo into my computers psu and never even got put in the bank. >x-P

    I should try big HV cap VS little LV cap he he!

    We are getting the thread off track though eh?

    -Ben
     
  13. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    I know several people that have touched the pins of a charged flash capacitor and it only made a small mark--hardly even worth calling a burn. I suppose it depends on where you are shocked, but the flash cap PROBABLY won't kill you. Of course, that is only if you don't wire a bunch of them together into a bank--Those can pack quite a punch and could really "mess you up."

    I don't think we're getting too off-track. I suggested using a flash cap, and right now we're simply talking about safety. I think it's completely legit.

    Der Strom
     
  14. unclejed613

    unclejed613 Well-Known Member

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    banks of caps can have their problems too...... like the "weakest link" failure, where one cap develops a problem and explodes because all the rest of the caps discharge through it at once....
     
  15. one-zero

    one-zero New Member

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    hello dear, i have need a 15w smps circuit with available parts list. if anybody can do it please help me ...
     
  16. unclejed613

    unclejed613 Well-Known Member

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    start a separate thread please.......... one topic at a time.......
    i got bit by an 800W Samsung switching supply that had the switching chip popped open.... full charge from two 470uF/250V caps in series through my left index finger from fingertip to the heel of my hand (never place a P/S board in your open hand, handle it by the edges until you've discharged the caps).... left a burn hole in the tip of my finger, and the involuntary reaction of my arm tossed the power supply across the room.... very painful. any cap MUST be treated with respect, especially if it's charged to anything above 25V. in the capacitance formula C=Q/V the charge is the numerator with voltage as the denominator, so as the voltage goes up, the charge is increasing MUCH FASTER.... so even at 0.25uF, the charge is fairly large... as large as a 470uF cap charged to 150V 0.075Coulomb if my math is right

    oooh!... ooooh!!! new award for threadjacking!!!!! the Yosemite Sam Award!!!!!!!!! "Mahh nayme is Yosemite Samm, and ahhhma hahjackin' this here thread!!!!!!"
     

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  17. lev77

    lev77 New Member

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  18. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Some of those values are cutting it extremely close. 16,000 volts, for one thing, is probably far less than what your ignition coil is putting out. Also, the current rating is significantly less than what you really need. I wouldn't recommend using this type of diode.
    Der Strom
     
  19. lev77

    lev77 New Member

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    just finished working on this need to know if its connected ok..

    thanks
    lev77
     

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  20. ouma

    ouma New Member

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    how many volts does a flyback produce?
     
  21. lev77

    lev77 New Member

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    hi ouma
    im not using flyback any more. this to connect car ignition coil to HV capacitor this is instead on rectifier
    thanks
    lev77
     

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