Electronics Poetry: "Power Supply"
September 1942 QST

Ode on a Power Supply? Well, maybe not really an ode, but this poem titled, "Power Supply," written by Eileen V. Corridan, appeared in the September 1942 edition of the ARRL's QST magazine. It is really quite entertaining and instructive! It applies to the original tube-based circuit as well as to modern solid state versions. I somehow get the feeling that this poem will now be republished in many places.

Power Supply

by Eileen V. Corridan

The how and why of a power supply

Is something very quaint.

It takes the a.c. current

And makes it what it ain't.

You start with good ole a.c.

But you need some pure d.c.

How the PS finally makes it

Is now quite clear to me.

First, gimme a primary winding;

A secondary, too.

Now I've got a transformer-

Let's see what it will do.

The primary takes the line juice;

Inductance does the rest.

But you gotta split the secondary

To do its job the best.

"Less turns in the coil for the heater,

More turns for the plate supply."

We've still got only a.c.

Which the tube will rectify.

Now we come to the moment

When tube and a.c. meet.

Just keep in mind a rectifier

Acts like a one-way street.

A.c. travels in wave form

From plus to minus, and then

It simply changes direction

And does it over again.

But the tube says, "Nothing doing-

This is no swinging door.

I'll take one-half of your wavelengths,

One-half - and nothing more!"

At least a half-wave rectifier

Would act about that way.

We'll use another plate in there

And thus save wave and day.

So now one plate says, "Come ahead."

It takes its half-waves through

The other plate is minus, then;

It has no job to do.

Then comes along the other half.

The second plate starts working.

So half and half are now a whole

While number one plate's shirking.

From filament to filtering

The current that is flowing

Is now d.c. - pulsating kind -

That toward the filter's going.

It isn't pure by any means.

Its ripples need some smoothing.

Chokes and condensers serve for this;

The waves find these quite soothing.

The filter circuit works like this:

In a condenser-input filter,

Inductance and capacitance

Keep pure d.c. in kilter.

Pulsating d.c. also has

Some a.c. current flowing.

Condensers short the a.c. out,

And chokes keep d.c. going.

And so at last like Ivory Soap

Our current's pure d.c. 

I must confess this whole darn thing

Has made a wreck of me, see?

Posted February 6, 2020
(updated from original post on 3/21/2011)