Re: PWM Controller question

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

Original poster: "tcbfw" <tcbfw-at-charter-dot-net> 

David,

Dan's explanation of this being a means to keep the coil operating at
resonate freq. during long arks makes sense, but as this is a first attempt
at this combined VVTC/SSTC topology it will not be my primary concern. The
tubes I've chosen to try this with are 810 triodes, so far I've gotten the
sockets wired to 4 independent filament transformers, it take about 200
watts to light them up, finished the PWM controller board tonight, but still
have to wind the grid transformers - same basic design Dan used in his
PlasmaSonic - just need a few more turns (takes about 180Volts to switch
that tube full on/off).

But enough about me and my project, with your (don't ask) statement I've
just got to know more . . . How much power was that AM station putting out ?
What was you experimental semiconductor ? Could you "hear" the unit as it
burned up ?

Can't wait for an answer,
Phil

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, June 20, 2004 7:59 PM
Subject: RE: PWM Controller question


 > Original poster: "David Trimmell" <humanb-at-chaoticuniverse-dot-com>
 >
 > Hey that is a good question, I wondered about that also. But, Phil, you
 > got my interest; you are going to Audio Modulate a "H-Bridge" of vacuum
 > tubes!? Holly cow! What mode? Triodes, Pentodes? Heck you have me
 > salivating on what possible design you may use?!! Of course, you can
 > also do it with IGBT's and drop the filament power needs and voltage
 > issues. I think Dan's PlasmaSonic design is good, but I could see some
 > improvements in using (possibly) rail modulation. Real high power plasma
 > audio modulation will be seriously cool! I have seen it while arcing
 > something "semi-grounded" to a AM radio station tower many years past
 > (don't ask!). My grid modulated VTTC has been the closest I have seen
 > yet, but quality was unreliable.
 >
 > Regards,
 >
 > David Trimmell
 >
Original poster: "Eastern Voltage Research Corporation"
<dhmccauley-at-easternvoltageresearch-dot-com>

This small feedback signal was a very basic attempt at allowing the system
to maintain constant tune even under longer arcs and
is basically inferior compared to the self-resonant topologies in use today.
This small feedback idea was one of Richie Burnett's and it does work to
some extent.

Dan

 > -----Original Message-----
 > From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > Sent: Sunday, June 20, 2004 4:02 PM
 > To: tesla-at-pupman-dot-com
 > Subject: PWM Controller question
 >
 > Original poster: "tcbfw" <tcbfw-at-charter-dot-net>
 >
 > Dan, or anyone else that might know the answer.
 >
 > Looking at your PlasmaSonic SSTC design,
 > more specifically the TL494 PWM Controller.
 > You have a feedback signal from the positive rail able to change the
 > frequency the circuit oscillates at, could you explain what the overall
 > goal
 > of that would be ?
 > I wanted to use the same controller IC, but drive an H bridge of tubes,
 > this
 > will make my positive rail in the thousand rather than hundred volt
 > range,
 > so the value of R27 thru R30 will be adjusted.
 > Just don't understand the need to have the frequency change with the
 > power .
 > . .
 >
 > Thanks,
 > Phil
 >
 >