[MrFixr55]

I know that this is an old thread but some light shed on why such an elaborate B+ Supply:
The "ladder" of Zener diodes was designed to act as a voltage divider that would provide voltages that would not vary with load. This is a power supply that was designed to power battery operated radios with rather high impedance and resistance for B and C voltages but how impedance for the A (Filament) voltages. The ARBE III uses the same Zener Diode Totem Pole but I am not sure that it uses the same voltage regulator in front of the Zener Diode Totem Pole. A small cap can be put on the output of the regulator, and 0.2uF caps can be put between each output and ground. I suppose that measuring the ripple in and out of the B supply when under load would help determine if it is the A or B supply that is causing the hum.

Most AA5 and battery tube radios that have built in power supplies do not have inductors in the filter circuit; they use resistors. So an RC filter circuit should work.

In one of my "experiments" I built a voltage tripler circuit with rather high value caps, in the order of 400 uF and powered it from a 24V transformer 500mA transformer. The output was rather low, and I burned my hand touching the transformer, finally figuring out that when a cap is supplied by pulsating DC as opposed to pure DC, there is current draw that is proportionate to the size of the cap, a lesson that I should have remembered from Physics II in college.

[RodB]

Just remembering you took Physics in college is impressive.

[MrFixr55]

Hi RodB,
Relatively easy to remember Physics II; I did well in it, as a lot of it was current electricity, Ohm's Law, etc. It is Calculus that I want to forget!! I remember that I took it, but I forget all about Calculus but the pain.

My theory regarding Calculus was that when that apple fell on Newton's head, it caused brain damage. He then went into a hebephrenic state, spewing irrational formulae. His scribes documented this gibberish, and it became Calculus.

[morzh]

My whole education is Physics. Electronics was self-taught.

[Paul Philco322]

I think I remember college....a smoky, boozy haze, something like that! I feel like an academic liteweight here when it comes to theory. Good to have strong trees to lean on here. Paul

[morzh]

If you mean an oak, that's me.

(PS. When in Russian someone is referred to as a tree, and especially as an oak, that means the guy is very,. well, dense)