Hello Andy,

Saturday, November 14, 2015


OK, but what about wire breakdown voltages? In all the big air cored
LF tanks I have seen the windings are well spaced on ceramic, or
Paxolin type grooved formers, how do I know a close wound toroidal
coil won't break down?


I have built a few HV supplies using decent industrial quality iron
cored transformers, the biggest is 5kV at 1.5 Amps, which can also be
fed from a 40 Amp Variac, to drop the primary down. I use that in my
workshop for running a glue drying machine.

I was also gifted some NOS ceramic triodes, some US, some Russian, and
would consider having a bash at a valved LF amp, just "because" :) I
have to say my limited experience of ceramic triodes has shown no
unreliability, in fact a zero failure rate so long as they are
gettered before use, if they have lain dormant for years.

I do have a reasonable collection of failed FET's though :) In
fairness user error was the demise of most of them.


Thanks Andy.


> I'll say it againV = 4.44.F.N.A.B  (all SI units)


> THAT is how you size ferrite cores.  It tells you more or less
> everything you need to know to make ferrite transformers.  Keep B to
> less than 0.1 at these frequencies


> But.. why would you want to use valves?
> Expensive, unreliable, high voltages...


> 'jnt








--
Best regards,
 Chris  2E0ILY                          mailto:[email protected]