Plasma Tweeter construction and repair
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One of my readers sent me a link to french article published in Audiophile n°4, April 1978 by Jon Hiraga.

Unfortuately I didn't understand french and the article is copied in pictures so translators would not work. But with the pictures and some interpretation I can write something about it.

This tweeter was produced by ONKYO in 1978.

Company Adress:

Real ONKYO, 4-4-16 Ueno-Dori, Nada-Ku, 657 Kobe-City, Japan.

As ONKYO was famos with their wooden sides on their amplifiers the tweeter was also availible with wooden plinth.

 

Schematic

Nothing really new, it was more or less a copy of the Ionofane. 

A main transformer was used. The feedback for the self oscillating tube was done from the elektrode with a fixed capacitor. A resonant coil (L1) was used and had to be trimmed to resonance with C1/C2. The principle is a mix between the fixed Magnat oscillator and the Ionofane's floating oscillator. The ionic tip was different compared to the Ionofane. In the picture below you can see the two coils.

Realon schematic