(HEC HT50, HT57) Vishay RF Power Barrel Capacitors are an alternative for HEC capacitors.

HT50 Series Ceramic Capacitors On High Energy Corp.

HT Series Ceramic Capacitors offer a high voltage, current, and power rating, in a small, RF-capable package. Their dissipation factor is low and their self-inductance is minimal. High-voltage industrial and broadcast environments demand extremely rugged capacitors. The simple structure of these components enables them to last for many years without requiring maintenance. We design our HT Series parts with a long flashover path and a nonconductive, moisture-resistant coating. A broad range of capacitance and temperature coefficients can be achieved by choosing from six different Class I dielectrics. Typical applications include transmitters, antennas, diathermy, X-ray, and induction heating.


Major RF power barrel capacitors producers in the world are HEC HT57 and HT57 series, and Vishay’s TOS 030033 and TOS 020016. Classic RF power capacitors are one of the major types (sometimes called “doorknob capacitors”). Among the major applications are anticore antenna emission, high frequency dielectric heating, microwave power supply, radar, and medical equipment.


Global supply chains are affected by the Covid19 pandemic, causing many industrial products, including HECs and Vishsy-Dralorics, to stop production. HVHF series high voltage HF capacitors are eagerly sought-after as an alternative by existing RF capacitors users. HVHF series high voltage HF capacitors are already approved by lots of manufacturers of RF power supplies and radar equipment.   

The USSR supported China’s construction of a high-level capacitor production line 70 years ago, and high-frequency ceramic capacitors have been around for 70 years. China’s ceramic dielectric powder manufacturers have been improving their production for decades, creating products like NPO, N750, N4700, Y5T, X5U, etc. Our brand of RF power barrel capacitor product is constructed using Class I and Class II dielectric materials. Low loss, high reliability, and high voltage ratings are the main features. Major application markets for HVC ceramic capacitors include RF power supplies, induction heating, medical equipment, gem smelting, and radar communication.

The following are the HVCHF series of HVC’s alternative replacements for HEC and Vishay’s 5FAE, 7FAA, 0300033, 020016 series, and HEC HT50, HT57, HH57, HT58, and HT59 series, HVC’s RF barretted capacitors as small as 20mm, 30mm, and 58mm. Custom sizes are also welcome.

Using a high-voltage doorknob capacitor, how can I test it?

To determine whether these capacitors are as good as new, I would like to test at least 30 (HEC HT57 100pf 15KVDC N750).

I don’t trust substituting them one at a time for a good evaluation, since they form a tank circuit of a Colpitts oscillator, four in parallel. According to my suspicions, either 1) the silver-soldered connection between the plates has gotten hot, or 2) leakage may have occurred, which indicates a breakdown and eventual explosion.

Load power is approximately 1.8KW, and the oscillator is operating at about 22MHz. Static leakage tests at high voltage and the use of capacitance checkers may not be sufficient to ensure that they are fit to do the work required of them. Using a 5868 at 500ma maximum capacity, 40% duty cycle, the load is an induction coil for an induction furnace.

If you could provide me with simple directions on how to conduct this test, and some examples of evaluating how close I am to the limits of the specification, I would greatly appreciate it. Are there any HAM Radio operators that can help me with this?

Despite trying to find test methods for capacitors of this type through googling, I have not been successful.

Obviously, I do not want to spend a lot of money on testing these, but I was wondering if you could divert some of the input of the tank circuit to a capacitor and measure it. Is that possible?