“D” Cell to “G” Cell Adapters

For Portable Tube Radio Sets, Revision A

By dsen333v

August 2011

10/3/2011 Revision A: Minor typo corrections, and added a

photo of Emerson radio set with adapters installed.

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Many portable tube radio sets

were designed to use one or two

1.5 volt “G” cells for their “A”

battery. The Eveready #964 “G”

cell “A” battery is shown here.

In this paper I describe two

easy-to-make adapter units that

use “D” cells and that are the

same size as “G“ cells. The

active adapter unit provides 1.5

volts to power the tube

filaments. The dummy adapter unit

carries a “D” cell just like the

active adapter, but there is an

insulator inside the dummy

adapter, so that no voltage is

present across the dummy adapter

terminals.

Explanation; Many of the portable tube sets used two “G”

cells wired in parallel. My experience with batteries in

parallel suggests it isn’t such a great idea. Therefore I

use one active adapter and one dummy adapter in these

radios. The dummy unit accomplishes two purposes; 1) it

carries a spare “D” cell and 2) it fills out the battery

compartment in order to preserve the original “look” and

weight distribution.

One modern alkaline “D” cell, such as the Duracell MN1300,

has roughly the same amp-hour capacity (15 to 18 amp-hours)

as two of the old “G” cells (estimated not more than 8 amp-

hours each, based on specification 4 amp-hours for the #950

carbon-zinc “Eveready Classic” D cell). When the active “D”

cell wears out, you can easily slide it out and swap it

with the spare from the dummy adapter unit.

A replica Eveready label may be found on last page of this

white paper.

“G” CELL REPLACEMENT DEVICE

AUGUST 2011

“G” CELL“D” CELL

ADAPTER PARTS LIST

1 1/4” X 20 TPI X 15/8” MACHINE BOLT

5 1/4” X 20 TPI HEX NUTS

1 1/2” I.D. X 11/4” O.D. FLAT WASHER

( CALLED 7/16” X 11/4” WASHER)

6 1/4” X 11/4” DIA. CARDBOARD WASHERS

(SEE INSTRUCTIONS)

1 11/4” DIA. CARDBOARD DISK

(SEE INSTRUCTIONS)

1 CARDBOARD TOILET PAPER TUBE

1 4” X 41/2” PLAIN PAPER INNER SLEEVE

1 “EVEREADY” PAPER LABEL

(SEE WRITE-UP FOR TEMPLATE)

1 ALKALINE “D” CELL

=

1 1/4"

1 11/32"

1 3/4"PLAIN PAPER INNER SLEEVE,

EVEREADY LABEL OUTER SLEEVE

4"

CARDBOARD CYLINDER

(SEE INSTRUCTIONS)

1 11/32"

Instructions for Active Adapter Unit

1. Use any ¼” machine bolt that is threaded all the way up

to the head and is at least 2” long. Cut the bolt shaft to

15/8” long (not including the head). The total length of the

bolt, including the head, should be exactly 13/4” when cut.

I used bed frame bolts for my first two adapters, which

resemble carriage bolts.

2. Make the cardboard washers and disk by using a ¼” x 1¼”

metal washer as a template, and a cereal box or similar

piece of cardboard as raw material.

3. See the photos below. Make the negative terminal piece

by soldering one of the ¼” nuts into the 7/16” x 1¼” steel

washer. The inside diameter of this type washer is ½” and

the hex nut should fit inside the hole with just a little

bit of “play”. If “play” is excessive, make a cylindrical

shim out of thin copper sheeting. Use resin-core solder

(electrical), NOT acid core (plumber’s). After the piece

has cooled off, use fine grit sandpapers or steel wool to

remove resin residue and to polish, as it may have become

discolored during soldering. Rinse off any remaining

particles with water and immediately dry with towel.

Washer and Nut Before Soldering

Torch, Solder, and Brick Work Surface

Negative Terminal Before Cleaning

4. Assemble the nuts and washers onto the bolt shaft as

shown in the drawing. Align the washers as best you can

before tightening the nuts, so that their rims will hold

the shape of a nice straight cylinder. See photos below.

5. Cut a toilet paper tube lengthwise. Lay it flat, mark a

cut line 1¾” from an uncut edge (so that when rolled it

will form a cylinder 1¾” tall), and cut along this line.

Form the cut piece around the washer assembly. Mark the

line of the overlap. Trim along this line. The goal is to

make a cardboard tube that is 1¼” inside diameter and 1¾”

tall, and whose cut edges just meet, with no overlap. Do

not tape the edges together.

6. Cut a piece of plain paper to 4” x 4½”. With the 4” side

in line with the axis of the batteries, wrap it snugly into

a cylinder around two “D” cells that are held together by

hand (do not tape the D cells together to hold them). While

holding the wrap in place with one hand, tape the

overlapped edge down (not to the batteries!) with two or

three small pieces of thin cellophane tape. Then remove

just one of the batteries. If the battery does not slide

out gracefully then the sleeve is too snug, and you may

wish to try again.

7. Form the cardboard piece you made in step 5, such that

you can start inserting it into the plain paper sleeve that

you made in step 6. The D cell that you left inside the

plain paper sleeve will help to support it during this

phase of assembly.

8. Before inserting the cardboard roll completely, start

inserting the washer assembly into the cardboard roll.

9. Gradually work the cardboard roll and the washer

assembly into the plain paper sleeve.

10. When successful, the head of the bolt will contact the

negative terminal of the battery, the cardboard roll will

be completely inserted into the plain paper sleeve, and the

negative terminal that you made should be almost flush with

the end of the cardboard roll.

11. Use gentle pressure as necessary to position the D

cell, the plain paper sleeve, and the cardboard roll so

that the overall appearance of the unit is satisfactory.

Use a voltmeter to check for 1.5 volts at the terminals, or

not, depending on whether active or dummy adapter type.

12. Wrap an Eveready label (or other brand, as you like)

around the completed adapter unit and tape down the

overflap, or you can glue the overflap to the underflap. I

chose to not use any glues in my adapters.

Instructions for Dummy Adapter Unit

1. The dummy unit is identical to the active unit, except

for one difference. Before inserting a “D” cell into the

adapter, insert a 1¼” cardboard disk that does not have a

hole in its center. This will insulate the negative

terminal of the D cell from the adapter bolt.

Emerson Model 850 with “G” Cell Adapters Installed

Here is a suitable paper label (provided you are not a

perfectionist). You should double check the dimensions on

your printed copy. You can resize the picture object if

necessary. This document was originally prepared using

Microsoft Works Word Processor and the picture size may

have changed slightly during conversion to MS Word format.

THE END