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Capacitor discharge ignition problem

Discussion in 'Misc Electronics' started by nospam, Jan 14, 2005.

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  1. nospam

    nospam Guest

    My bike was running yesterday, wouldn't start today and after much
    investigation it is looking like the ignition module is dead.

    It is of course completely encapsulated and damn expensive to replace so I
    was looking for a second opinion on what I observed.

    The unit is by Kokusan Denki, it has one output to the ignition coil, the
    other side of the coil is grounded.

    I lashed it up on the bench with a coil.

    On applying power it draws little current and sits there 'ticking' at 20 or
    30 Hz, it did that on the bike but I don't know if it always used to.

    I looked at the drive to the coil with a scope and the 'ticks' are actually
    driving about a volt across the coil for about 200us. The coil is about 1.5
    ohms.

    Doesn't look right to me.

    I tried powering it with the coil disconnected and I could hear the
    inverter, err, 'inverting' at some high frequency, the voltage on the coil
    drive output went negative and quickly past full scale on the 1kV range of
    my meter.

    Seems to me the pass element (SCR or whatever they use) has gone short
    circuit. So with the coil connected it is just current limiting or
    something trying to charge up the coil. With the coil disconnected I am
    seeing the capacitor voltage on the coil output, but, at over 1kV it seems
    rather high. Maybe the inverter has lost regulation and the excessive
    voltage killed the pass element? Anyone know if 1kV + is normal for a CDi
    unit?

    Does anyone think the unit isn't dead?
     
  2. Jamie

    Jamie Guest

    before you deside its the mod, try putting a plug on the coil.
    and then just power up the - + with a batter for a .5 or so to
    see if your getting any form of spark on the plug.
    1.5 ohms seems low to me.
    but i could be wrong..
     
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