by Eeyore <rabbitsfriendsandrelations@[EMAIL PROTECTED]
>
Apr 22, 2008 at 02:54 PM
John Byrns wrote:
> "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote:
>
> > Can I suggest a topic for you? A current limiter for tube heaters.
> > People are keen to use voltage regulation, which doesn't seem to
> > me to be so important. Heaters are specified at +/- 5% so
> > anything between 6V and 6V6 for a 6V3 heater is within tolerance,
> > and with a wirewound pot between two 'lytics one can get it spot on.
> > But heaters draw huge currents at switch on. Do you have a circuit,
> > using those funny black things with shiny legs, that could current
> > limit? Two circuits would be of interest. One at say 1.2A
> > (a pair of B9A's) and one at 3A (a pair of EL34's)
>
> Your comment "one at 3A (a pair of EL34's)" suggests that you are
> contemplating running the EL34 heaters in parallel, this seems like a
> singularly bad idea to me. Unless the heaters in both tubes are
> identical the current will divide unequally between the two heaters.
So what ? They're designed to be run at a given VOLTAGE and the voltage
across both will be identical.
> There is also no guarantee that you will get 6.3 volts across the
> heaters
Uh ?
Graham
