Re: Tube TC

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mike" <induction@xxxxxxxxxxx>

Hi Bob,
              It does look like they forgot to draw the B+ from the 
junction of the lower triode's RF Choke and it's bypass cap up to the 
power supply. I also would have added grid current meters between the 
grid resistors and ground and in series with that, current overloads 
to trip the control system.
Beside taking the feedback from the secondary, this looks very much 
like a Thermatool H.F. welder VT-160.
That machine uses a pair of 6696A triodes, uses the same cap divider 
taking signal from the opposite side of the tank.
The output is either a standard work coil or more typical, an RF 
transformer with 14 or 16 to 1 for contact welding or 14 or 16 to 2 
for induction welding at pipe mills.
The only thing about that design is the grid current runs lower at 
heavily loaded conditions, maybe 5 percent Vs the usual ~ 15 percent 
of an inductively coupled grid coil . Overall, after losses, these 
give about half the power out as the Edison line input.
That's one reason the solid state machines are more used now.
Still, interesting beast.
Mike

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, October 16, 2005 12:50 PM
Subject: Re: Tube TC


> Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>
>
> Hi,
>
> Yes there appears to be a few peculiarities with the circuit. No voltage to
> the lower tube, strange grid drive configuration, feedback form the
> secondary and how does it work in class C with a series tank circuit with no
> freewheeling path for the anode current? I bit like running igbts without
> freewheel diodes on a series resonate primary. Perhaps the tank circuit has
> a missing parallel C or it was it was intended to operate in class A.
>
> An observation of the losses in the tank L. In general center tapped push
> pull windings are less efficient  for a given weight of copper  because the
> rms current is higher for a given average current. This is similar to a
> center tapped mains transformer using two diodes i.e. only half the copper
> is being used only half of the time. With a tuned circuit I suspect for a
> given power and weight of copper there would be no difference.
>
>
> Robert (R. A.) Jones
> A1 Accounting, Inc., Fl
> 407 649 6400
> ----- Original Message -----
> From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Thursday, October 13, 2005 9:10 PM
> Subject: RE: Tube TC
>
>
> > Original poster: Sparktron01@xxxxxxxxxxx
> >
> > Hi Malcolm,
> >
> > http://hot-streamer.com/temp/C-027.pdf
> >
> > Try the Google search, the URL is long and if it is truncated
> > you may go places that aren't expected...  ;^)
> >
> > That is an excellent paper and shows how a high power
> > (>5kW) VTTC power system  _should_  be built.  Save the PDF
> > to your hard drive, it is a good reference.
> >
> > Best Regards
> > Dave Sharpe, TCBOR/HEAS
> > Chesterfield, VA. USA
> >
> >
> >
> >
> >  > Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>
> >  >
> >  > Hi Dave,
> >  >
> >  >  >
> http://www.veccal.ernet.in/~vecpage/inpac2005/CD/Contributory%20paper/
> >  >  > C-027.pdf
> >  >  >
> >  >  > NOTES
> >  >  > I.  There is a schematic error in the above URL, can anyone catch
> >  >  > it??? (and it is
> >  >  >       NOT minor...  :^D )
> >  >
> >  > Even the url doesn't seem to be working ;)
> >  >
> >  > Malcolm
> >  >
> >  >
> >
> >