Transformer
 

On Mar 30, 2:03*am, "Howard K0ACF" wrote:
Check Signal Transformer, they are sold by Digi-Key & many others. They make
some dual secondary that are very small but plenty of current for what you
are going to use it for. I used many of them in Progressive Systems for
Electronic Gaming Machines."JIMMIE" wrote in message

...



I am looking for a source of a very small transformer that will supply
125 VAC on the secondary and enough 6.3 VAC with current for 1 or two
small tubes. Something on the order of a 12AX7 or 2. Small physical
size is important. I need to be able to shoehorn the whole thing
inside of a double outlet box.

Jimmie- Hide quoted text -

- Show quoted text -

Not clear on the OPs application but ............
12AX7 double triode takes 12.6 volts on its heater at IIRC 0.15 amps?
BTW 12.6/0.15 = 84 ohms (hot).
Another approach if circuit isolation permits it, is to 'drop' voltage
for the heater re-actively by using a capacitor.
If 125v AC is available?
For example 125 minus 12 = 113 volts to be 'dropped'.
The reactance of a capacitor rated for 'peak' voltage of around 180 -
200 volts; RMS = 120v.
113/0.15 = 750 ohms approx. (Since it's mainly reactive no need to get
into a vector diagram!).
Since Xc = 1/2pi.f.C A one microfarad cap. has a reactance of about
2650 ohms.
So 2650/750 = 3.5 microfarad (AC capable). In practice it'd probably
work with anything from 3 to 4 mfd. A not too unusual size of AC motor
cap is 3 mfd. But cap. size consideration.
Just floating an idea. Have only tried this on experimental basis but
it worked!
And IIRC it was a 12 volt surplus WWII tube that we used. The same AC
rectified, filtered with a capacitor, provided B+ for the experiment.