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Re: MMC Cap up in Smoke

Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>

Tesla list wrote:

Original poster: gary350@xxxxxxxxxxxxx
Are you guys using any special type capacitors?
I built my first MMC capacitor today it lasted a whole 2 seconds then went up in smoke. My power supply is a 6K 20ma transformer. The capacitors are .1uf 1500VDC Sprague 430P 227084-43F. I soldered 7 capacitors in series to get 10.5K volt rating. My TC is a tiny little thing I built 5 years ago it had an oil filled poly cap.
Here is a picture on the TC.
Notice the small TC in the bottom left with a 1.5" diameter 5" tall secondary with a door knob top load.

Hi Gary,

You need to use polypropylene (PP) film caps such as CD 942C, Sprague 710C, Panasonic ECW-H, WIMA FKP1, etc.

Unfortunately, the Sprague 430P series you used is a polyester (Mylar) cap, and is unacceptable for RF use. Even using PP caps, you may want to use a DC rating that's _at least_ 2X the RMS rating of your HV transformer. Using 3X the RMS rating would be even better (longer operating life).

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