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MMC partial failiure
Hi All,
my little coil's mmc seems to be undergoing some sort of weird
failiure mode.
The coil functions normally, throwing nice 18" arcs and drawing 80ma -at- 5kV,
then it starts to pulse in and out of tune.
The secondary discharge stops almost totally and the spark gap makes the sort
of hiss that is does when the coil is very badly tuned. After a few seconds
it pulses back into tune only to drop out again and repeat what I have
already described.
My theory is that in one of the 3 strings of caps is a cap close to death and
that it is breaking down reducing the capacitance of the string and taking
the coil out of tune, then self healing a bit then breaking down again.
Unfortunately not having an accurate C meter I can't measure the strings to
check this.
The caps are 1600V 47nF philips 378 series in strings of 10 with 3 strings in
parallel and the neon is a 6/60 (I said 80ma 5kV because it sags quite a lot
under load)
It is not a reso-cap so I don't see how a large enough voltage to damage the
caps is being generated off a 6/60 neon?
Semi-baffled in GB
Nick Field