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Re: Tube TC



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 > > > > > >