Re: Toobz the rating game

To: tesla-at-pupman-dot-com
Subject: Re: Toobz the rating game
From: Dan Gowin <gowin-at-epic-1.nwscc.sea06.navy.mil>
Date: Wed, 08 Jan 1997 09:35:18 -0500
Subscriber: gowin-at-epic-1.nwscc.sea06.navy.mil Wed Jan 8 22:23:42 1997
Tesla List wrote:
> 
> Subscriber: hullr-at-whitlock-dot-com Tue Jan  7 22:29:53 1997
> Date: Tue, 07 Jan 1997 17:36:46 -0800
> From: Richard Hull <hullr-at-whitlock-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Toobz the rating game
> 
> To those interested in Toobz,
> 
> With the arrival of John Freau ( tube coil guru) and Robert Stephen's
> high powered monster, a lot of interest in tube coils and their variants
> is occuring on this list.
> 
> For those not around during the old days, the tube must seem a bit
> strange.  Actually they are more akin to a virtually indestructable FET.
> 
> The most interesting characteristics of tubes is that they are rugged and
> still available in ever decreasing numbers at hamfests for reasonable
> prices.  The day will come when tubes we take for granted today will be
> antique and collectable curios.
> 
> Tubes are most often applied in Tesla coils as amplifiers sent out of
> control to form an oscillator.  This form of tube coil is interesting but
> a proven power hog and low spark producer.  John Freau's Staccato mode of
> operation has made the longer spark tube based system a reality albeit in
> slower pulsed mode.  The Hydrogen thyratron can actually sub for the raw
> air gap in special case scenarios.
> 
> The choice of a tube is all important and the ratings and specs for them
> are confusing to non-tube folks.  John Freau has a knack for running his
> tubes far outside the spec sheets.  Only tubes will allow this.  Also
> natural intermittent duty cycles associated with Tesla systems allows the
> tube to be strained severely without immediate destruction.
> 
> In general, a bit of "fast and loose" can be played with the
> specifications of these devices.  For instance, the 4C35 hydrogen
> thyratron can handle 380KW of peak pulse power, have 8KV on its plate,
> and  see as much as 100 amps of peak plate curent with a PRR (pulse
> repition rate) of 1000pps. The recommended max on time is 4-6usec.  If
> you can live with 200pps the peak current can double.  If a 1-2 usec on
> time is used at 200pps the peak current can increased again.  It is a
> matter of balance.  Learning to operate tubes wisely is an art.
> 
> If you are like John and I, the normal operating parameters are taken as
> the barest starting point and the absolute max ratings column on a
> manufacturers spec sheet is accepted as standard proceedure!  Double the
> max ratings are where we like to operate normally.  This usually shortens
> tube life by 200 to 500% or more.  Thus, if a tube would normally
> function for 1000 hours then we get only a few tens of hours.  Based on
> the frequency of use of a coil, this can be many years of operation.
> 
> I'll be curious as to how many here actually venture into tube systems.
> Be prepared to hamfest for parts critical to this special area.
> Actually, the hamfest will readily yield far more tube coil related parts
> than disruptive parts.  Very tubular guys!
> 
> Richard Hull, TCBOR

Richard,
	I'm personally looking for a pair of RCA 573B
power triodes or any high power 811 equiv. It seams
these high powered triodes are still used in guitar
amps. But most of the dealers I've talked to want 
$50 US or more for these tubes. 
	Do you have any idea how much one of those 
power triodes, that Radio and TV stations use cost? 
You know, the ones that need forced air cooling 
and come in ceramic/metal casings. I've heard that 
the specs on these devices are high enough that a 
pole pig can be used as a plate supply.

D. Gowin