15V      .------.
-----o---| 7812 |---o----> 12V
     |   '--.---'   |
    _|_     |      _|_
    _ _470uF|      ---  104 cap
     |      |       |
    _|_    _|_     _|_


I found out thru' experiment that the problem of the input EL Cap of 470
uF, 25 V cause the fire spike when I insert the adaptor jack into the
socket.

If I use input cap of 10 uF, 50 V. The spike is smaller, still have.

If I take out the input Cap from the above circuit, no more spike.
Hence, I decided not to put any cap at the input of the 7812.  I believe
this is the better solution.

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