This weekend, I messed around a little bit with the Mystery Control portion of my 41-616.

As you may know, in the alignment instructions for these sets, the 2A4G is to be removed and replaced with an “aligning adapter” that has a red and black lead. However, no hint whatsoever is given as to what pins the red and black leads connect to in this “aligning adapter.”

Well, folks, I believe I have solved this “Mystery.”

I picked up a little analog multimeter today just for this purpose. I discovered that by using pins 5 (2A4G grid) and 8 (no connection inside the 2A4G, more on that later), it is very easy to align the Mystery Control circuitry using an analog multimeter or VTVM (the instructions call for a VTVM).

I have now fabricated my own “aligning adapter,” and I am going to tell you how you can do the same in a few minutes.

First, though, let’s look at the Mystery Control portion of the 41-616 circuitry.

The red lead should be connected to pin 5 (grid) of the 2A4G. As for the black lead, there is a wire under the chassis connected between the plate of the 6ZY5G and pin 8 of the 2A4G tube socket.

The 2A4G does not use pin 8 internally. And nothing else connects to pin 8 of the 2A4G socket, so it is not being used as a tie point.

I reasoned therefore that this must be where the black lead goes.

I tried connecting the analog multimeter between pins 5 and 2 and obtained a reading, but I seemed to get a better reading using pins 5 and 8.

How to make your own aligning adapter

You need an old octal tube base, one from a “G” type tube so it will fit inside the socket and tube shield base. Make sure the tube base you use has pins 5 and 8!

Solder a red wire inside the tube base to pin 5.

Solder a black wire inside the tube base to pin 8.

Your aligning adapter will look like this:

The image has been resized to 945x709px. Click here to show the original size of the image.

How to Use:

Follow the factory alignment instructions, and use your new homemade aligning adapter when the instructions call for using this.

Set the multimeter to the highest AC voltage range, setting it to a lower range if necessary. Do not start at a low AC voltage range, or else you may damage your meter.

Red lead of the meter to red lead of aligning adapter, black lead of meter to black lead of aligning adapter.

This will yield a much more accurate alignment than merely watching for the 2A4G to glow, as called for in the 1939 alignment instructions.

Here’s a look at the aligning adapter in use, connected to my new multimeter:

The image has been resized to 945x709px. Click here to show the original size of the image.

When a signal is applied from your signal generator to the input screw terminals where the Mystery Control loop antenna is normally connected, you will achieve a very high reading on your meter. Notice in the photo above, the meter is set to the 150 volt AC range, and it is reading around 90 volts AC! So be careful, and do not touch the leads when performing the Mystery Control alignment! Safety first!

WARNING

Be sure that you never, ever touch pin 3 of the aligning adapter! There is raw AC on pin 3, and it is not isolated from the household AC line! A good way to prevent this from happening is to fill the tube base with hot glue, not completely, but just enough to cover all of the pin connections inside.

Hopefully this will prove helpful to you whenever you need to align the Mystery Control circuits of 1939-1942 Philco sets.