RE: MMC partial failure
Sounds like you're spark gap may be overheating. I had the same symptoms
last Sunday when I forgot to turn on the SG blower (but I was running way
Brian D. Basura
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Monday, July 26, 1999 4:12 PM
Subject: Re: MMC partial failiure
Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
Carefully look at the caps. Almost always you will see that they
swelled up or the case has split somewhere. However, 5kV should be far
below any voltage breakdown. and three strings should not be stressed
either at this voltage. I would definitely suspect something else is going
on... Don't know what but maybe the gap is overheating or the variac is
burning a brush... I have seen sync rotaries loose sync and do this...
At 12:56 PM 7/26/99 -0400, you wrote:
> my little coil's mmc seems to be undergoing some sort of weird
>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
>of hiss that is does when the coil is very badly tuned. After a few
>it pulses back into tune only to drop out again and repeat what I have
>My theory is that in one of the 3 strings of caps is a cap close to death
>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
>The caps are 1600V 47nF philips 378 series in strings of 10 with 3 strings
>parallel and the neon is a 6/60 (I said 80ma 5kV because it sags quite a
>It is not a reso-cap so I don't see how a large enough voltage to damage
>caps is being generated off a 6/60 neon?
>Semi-baffled in GB