This page is meant to help those new to HV engineering to recognize HV capacitors by sight.  This is an essential skill for those who frequent junk yards, swap meets, Hamfests, yard sales, etc.  This page was created in cooperation with Scott Hanson.


Ceramic doorknob capacitors.JPG (130578 bytes) Doorknob Capacitors

Ceramic "Doorknob" capacitors.  These are primarily used as RF bypass caps in tube coils and are used for NST filtering applications in spark-gap coils. 

mica_cap.jpg (28868 bytes)

green_mica.jpg (14516 bytes)

Mica Transmitting Capacitors

 Perfect for the tank circuit on Tube Coils.  This type of capacitor was designed to handle high RF currents. 

The second picture is of a Reconstituted Mica Capacitor.  It doesn't look like the typical Mica Capacitor but was put in here to prove a point - Always read labels on anything that you don't immediately recognize.  There are also tell-tale signs to look for -  Porcelean Insulators are always a good sign.  The raised plastic rib on these capacitors were a good hint that they may have been designed for high voltage.  You will see a modified version of this on the Maxwell cap shown below.

vac_variable.jpg (25075 bytes) Vacuum Variable Capacitors

These make a good companion for the Mica Transmitting Caps shown above in the tank circuit of a tube coil.  They can handle large RF currents because the only dielectric is the vacuum.  They are adjustable.  The larger one in the photo can adjust from 10-400pF and the small one is good for about 100 pF.  The crank on the bottom either raises or lowers the bottom cylindrical plate.  Actually, both plates are composed of multiple meshed rings.

Professional HV Caps such as Maxwell Pulse Caps manufactured for Lasers.

These are the absolute best find out there.  They are perfectly suited for disruptive Tesla Coils.

mmc_top_small.jpg (12562 bytes) MMC (Multi-Mini-Capacitors)  -- Go to my MMC & Rolled LDPE page

THE best choice for most small hobbyist Tesla Coils.  They are made from metallized polypropylene film.  You want to be sure to get metallized polypropylene instead of metal foil because the metallized PP tends to "self heal" after a failure.  The metal foil caps become totally useless the second the dielectric is punctured.

Rolled LDPE Caps -- Go to my MMC & Rolled LDPE page

This was the standard hobby sized TC cap a few years ago.  They work great but are big, heavy, oily, expensive, and require lots of time and skill to manufacture.  No wonder MMCs have made them obsolete!

Error in txt of photo, should read "(2) at .018 uF"instead of "(2) at 0.027uF"

air_variable.jpg (21153 bytes) Air Variable

These are rumored to be acceptable in the tank circuit for lower voltage tube coils.  I suspect corona would cause lots of problems at anything beyond several KV.  They are commonly used in old tube amplifiers.

PULSECAP.JPG (87819 bytes)

Large Pulse Discharge Capacitor

It isn't much use for Tesla Coiling but is a great toy in other ways.  This is the type of monster cap that crazy people use to build coin shrinkers and exploding wire devices.  (See my Pulsed Power Work)

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