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Re: [TCML] Rectifying a Tesla coil



Hi Kurt,
I have some better info and pix of such a tube in some of my old books. I will dig them out and make some scans for you. Will be in Oct as I will be gone for a month soon.

Early X ray outfits were operated by either an induction coil or static machine. Induction coils had either mechanical interrupters, electrolytic or mercury ones. They typically operated in the audible frequence range, anywhere from about 500 to 2000 cycles with some mercury turbines getting to around 10,000 cycles. The magnetics of the coils precluded them from operating much higher, hence the air core coils were used for higher frequencies, such as the Tesla coil.

Frank

At 05:09 PM 9/1/2008 +0200, you wrote:
Hi Frank,

thank you for the nice characterization of the tube. Information about it seems to be quite sparse. My other comments interspersed...

Frank wrote:
Hi Kurt,
Very nice find, I have been after one of those tubes for years!
If you even want to part with it, drop me a line.

Unfortunately it's the only one I have, and I like to keep it.

It is actually not a "true" rectifier in that it was used with an
induction coil, which is pulsating DC, to block the inverse voltage
on larger coils. Typically it was used with coils of 12" spark
capability or larger as the inverse became significant and damaged
the X ray tube.

Yes, about similar to the point and plane "recifiers", about which was the talk.

They were of limited use before the vacuum level had to be adjusted.

Probably you noticed the 2 additional electrodes in picture:
http://home.datacomm.ch/m.schraner/Villard0696k.jpg
Guess, they are there for regulating vacuum level (like in X-Ray tubes).


The apple green glow you see in at the cathode in your operating pix
is soft X rays being produced.

I'm aware of that, and don't like to take risk of exposition, without having available a dosimeter or Geiger-counter at hand, to check it.

The geometry of the tube made a high resistance in one direction of
current and a low resistance in the other. It still had a significant
voltage drop when conducting and was for 5-10 ma currents!

It is not really a high frequency tube either, operating frequencies
were around 2000-5000 Hz.

Where is to be found information about upper operating frequencies of low pressure gas filled tubes? (IIRC thyratron tubes as well, are limited in frequency, H2-filled the least).

Again, nice pix!

I would not recommend you continue to use it on your TC tho as it
will damage it, especially if you draw an arc from it.

Having bad experience of the kind with a Geissler tube, I never considered to use it with a TC!

Frank

Best regards, Kurt

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