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Jet Engine Igniter Box

Discussion in 'Electronic Repair' started by Ted, Apr 18, 2007.

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  1. Ted

    Ted Guest

    I need to fix an igniter box, I suspect it might be the high voltage
    rectifier, what modern equivelent could I use for the rectifier diodes?
    The box is a rotax type NB 25/3, 24 volts in, 2kv out, 12 joules.
    It's a simple circuit comprising of a trembler mechanism, induction coil,
    rectifier, choke, reservoir cap, discharge gap.
    When I apply 24v, the trembler buzzes as normal but no high voltage. Any
    ideas?
     
  2. James Sweet

    James Sweet Guest


    A microwave oven diode would probably do the trick.

    Is this for a manned aircraft? If so then I'd hesitate to make any sort
    of substitutions even if they're likely to work fine. There's a lot of
    regulations surrounding that, and for good reason.
     
  3. Ted

    Ted Guest

    It's for ground use only.
    The microwave diode is a good idea, what is the rating for these?
    Any other suggestions of common faults with igniter boxes, I'm only guessing
    it's the rectifier, haven't made any checks yet.
     
  4. James Sweet

    James Sweet Guest


    A common rating is 12KV 500mA, I've never worked on one of these boxes
    but I'd start by checking for bad solder joints and then check any
    generic semiconductors, it sounds like a pretty simple device. If you
    happen to be near Seattle I'd be happy to take a look at it just to dig
    into something I've never seen before.
     
  5. Stan

    Stan Guest

    }I need to fix an igniter box, I suspect it might be the high voltage
    }rectifier, what modern equivelent could I use for the rectifier diodes?
    }The box is a rotax type NB 25/3, 24 volts in, 2kv out, 12 joules.
    }It's a simple circuit comprising of a trembler mechanism, induction coil...

    The simplest test would be to check the primary & secondary of the induction
    coil for continuity. Have you?

    Stan.
     
  6. Ted

    Ted Guest

    The simplest test would be to check
    the primary & secondary of the induction
    The primary is .5ohm, the secondary+ diode is 6M.
    I removed the high voltage cap and is measures zero ohms.
     
  7. James Sweet

    James Sweet Guest


    Sounds like that's your problem then. The cap should measure open circuit.
     
  8. Guest

    Amen to that except: If it is an electrolytic cap, resistance will be
    in the megohms after it stabilizes, but *not* 0. If it is a film cap,
    then resistance should be as near-infinite as matters, but again
    *after* it stabilizes. I am also assuming it wants to be an AC-rated
    cap as well? If so, please be sure to replace it with a similarly
    rated cap.

    One last thing, if this is an electrolytic cap, make sure it doesn't
    bite you. Discharge it before handling it.

    Peter Wieck
    Wyncote, PA
     
  9. Clint Sharp

    Clint Sharp Guest

    Discharge any caps that are used in high voltage/energy circuits, they
    don't need to be electrolytic to carry a nasty amount of charge.
     
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