Re: VTTC -715B

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Sharpe by way of Terry Fritz <twftesla-at-uswest-dot-net>" <sccr4us-at-erols-dot-com>

Ed P, John G., David T., All

Thanks for the quick response!  This list is the greatest technical
reference for
what we enjoy!  Yep, it looks like I may have an interesting opportunity here!
>From everyone's postings, and what "skunk works" I was able to do at work
today, suggests that this tube was in a lineage of:

Raytheon 715B, Raytheon 715C, Eimac (et al) 5D21, 4PR60C.  The 4PR60C
is in fact still being manufactured by ETD according to web sources (since
glass
envelope tubes was spun off by Emiac/CPI several years ago).

26.2VAC fils, -at- 2.1 A (oxide, NOT thoriated tungsten)
Vsg ~1250VDC
Ec ~  DK (don't know!!)
Vpk max 15-18kV (depending on source)
Ibpk 15A
Ppk 330kW(!!!!!!!!  :^) )
Pulse duty cycle on tubes like this are usually in the 0.1% (1 part per
thousand)
regime (100us -at- 10PPS).  Ed P. and John G., any old schema on radar
modulators and help on a suitable -grid bias / application help on using these
guy's would be helpful and appreciated!!

What I'm imagining is suppose you used (2) matched MOT's
in anti-parallel series (or small PT) in the 2.3-5.0kV range)
driving a balanced biphase voltage quadrupler (~10kV-12kV),
charging through a CuSO4/water resistor a 6 uF cap.  Using an 811A
grid modulator (remember that circuit John Freau? [hi!] ) run a low
pulse rate staccato (or super staccato of 2 or 4 pulses), with Ec of 300J.
This stored 300J is discharged in ~4ms, at 1PPS.  This equals peak
power of 300*2/.004 or considerably in excess of 100kW, driving a
pair of 715B's in push-pull; self excited hartley power oscillator
configuration.  With ~ 25kWpk, I was getting 18-19" push-pull
so using square root extrapolation, this guy would be easily double
that (~36-40").  I guess we could call this thing ULTRA-STACCATO.
I'm afraid of even thinking about this CW spark length out of a pair
of diminutive tubes like this...   (yea, right! )     :^D

Thanks for everyone's help on this one...

Regards
Dave Sharpe, TCBOR
Chesterfield, VA. USA


Tesla list wrote:

> Original poster: "Ed Phillips by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>
>
> Tesla list wrote:
> >
> > Original poster: "David Sharpe by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <sccr4us-at-erols-dot-com>
> >
> > Terry, ALL
> >
> > Got lucky today at Richmond, VA Frostfest and picked
> > up five (5) NOS Raytheon 715B tetrodes for nearly
> > nothing, still in original boxes.

> ....SNIP

> Dave:
>
>         If you haven't found what you want by the time you get this, let me
> know and I'll send you enough to get you started.  Those tubes were
> intended for ~15 kV hard-tube magnetron pulsers, and take an awful lot
> of drive.  I suspect they would be interesting for a self-excited VTTC
> using a rectified NST or set of MOV's for power supply.
>
> Ed