A typical booklet from 1933 provides
an illustration of the point radio had reached only ten years
from the commencement of national broadcasting. Battery powered
sets were rapidly being superseded by mains powered sets.
Click the front page
to read the catalogue, including the enclosed letter to the customer
(note its about 7 MBytes)
If you'd like to buy
one or two items you could try filling in the form and posting
Here's another booklet
produced by Cossor produced about the same time.. no battery
eliminators included, but you can see the type of batteries used
and their prices. Click
on it and see the whole booklet.
I also found an advert for Telsen
battery eliminators in which one of their selling points is "an
artistically finished metal case" because they wanted to
make clear the top item would be suitably covered up perhaps?
This was included in the magazine
"The Telsen Radiomag" Vol 1 Number 6 which is very
coy about the date of publication. I did notice though that Daventry
is noted as being on 1500 meters and, as this only started in
1934, the magazine must date from no earlier than this... not
much later however as Telsen went bust by 1935 and, after being
purchased from the Receiver, made domestic electrical appliances.
You can read Issue 1 of their
I wonder why the company folded?
Maybe there's a clue in their magazine as Issue 1 seems to have
one advert and Issue 6 no adverts. That is for anything not made
by Telsen. If you look at other magaziunes of the period you'll
see they were financed through advertising. It seems Telsen was
basically charging radio enthusists for their parts catalogue.
The Ekco company were
leaders in the manufacture of mains eliminators and battery chargers
for radio sets
(click the valve to read more)
Here's an early advertisement
from 1928 which covers a total of 16 models. Their new factory
at Leigh on Sea had just been opened and the company was just
starting out on in real manufacturing. Note the crafty way of
increasing published prices by excluding the valves essential
for operation of their equipments and Mr Marconi's tax. I'm not
sure this practice would be tolerated nowadays. Here's my £3:7:6d
can I have an M2 please. Not unless you shell out another 25
bob mate. That's £4:12:6d. Forget about 20% VAT, that's
a whopping 37% extra... and don't forget that Marconi pinched
18.5%.. almost like paying modern-day VAT to Marconi, just because
he had the foresight to buy radio patents.
I'm now wodering anbout the
ad... As the magazine from which this advert was taken was aimed
at retailers, presumably the prices are fixed selling prices
and don't include wholesalers discount, retailers profit and
Why did Ekco and others use
the tactic of adding valves as extras? Why not just offer their
products fully assembled ready for use at higher list prices?
It was all a subterfuge. You bought your battery eliminator from
Ekco then popped round to your local wireless shop who had a
range of foreign valves under the counter. Here you are sir a
nice rectifier valve for your M2.. that'll be two and sixpence..
Click on the front page
below to see the whole booklet. This was my grandad's and you'll
see some notes he made in 1932 including one about the years
guarantee for his battery eliminator running out in December
1933. He was born in June1885 so would have been 47 when he made
the notes, including the wiring to the mains adaptor. Ring mains
were unheard of and skirting board sockets rare. Mostly things
were plugged into a light socket. Sometimes three or four sockets
dangled under the light bulb...
You'll see, if keen-eyed, the
mains adaptor on the 1928 M.2,A.C. above looks different to that
below. It was probably turned from wood whilst the newer one
is in bakelite.
Bakelite is another story. Such
was the pressure from wireless manufacturers on the government
Ekco were forced to open a bakelite manufacturing plant to circumvent
duties imposed on their importation of bakelite radio cabinets
from the continent. I wonder if they made their own bakelite
mains adaptors in their factory? Who knows??
The following models
are from their later range, introduced about 1930 See
some earlier models
The Ekco AC12
Model AC12 with its case removed
Stamped on the chassis is the Serial No 247149
Ready for refurbishment is this Ekco
Model AC12. Ekco made battery eliminators from 1925 and the booklet
(left) dates from August 1931. In it are described seven models
for AC mains and one model for DC mains. Written inside the back
cover in my granfather's handwriting is the note that the guarantee
expires in December 1933. He must have purchased his model in
time for Christmas 1932. Other similar models were the AC18 and
Specifications for two typical
standard AC models available in 1931 are given below:-
120 volts up to 12mA or 9mA
if the 80 volt 2mA or the SG 60-80 volt 1.5mA tappings are in
120 volts up to 18mA or 150
volts up to 13mA or 14mA and 9mA respectively if the other HT
voltages are used
Adjustable 50 to 90 volts up
Lower voltages obtained with
base connector screw in position "L", when 100 volts
at up to 14mA to 120 volts at 10mA depending on drain from other
There were a number of AC mains
models which included battery chargers, two of which are described
As the AC12 but includes an
accumulator trickle charging output
As you can see in the picture
above, the design of the AC units is pretty basic, using a double
wound mains transformer, an iron cored HT choke, a capacitor
block and some resistors. Rectification was carried out by a
small, finned, full wave metal rectifier. Voltage outputs were
dependent on the amount of current being drawn. This is due to
the relatively high resistance of the rectifier and the use of
resistors to provide the lower voltage tappings.
The Ekco K25
click picture to see large
This model is larger and heavier
than the others depicted in the catalogue shown above and carries
the label "Combined Unit" as like the K12 includes
an accumulator charging facility or filament supply as well as
an HT supply.
are tappings for 200-225v and 225-250v mains at 40-100 cycles
and also a setting for 2, 4 or 6-volts. this would allow the
unit to feed either an accumulator or a set of indirectly heated
valves. If directly heated, battery type, valves were to be fed
directly the level of hum from the crudely rectified low voltage
would be overpowering but this rough low voltage DC supply would
be perfectly good for mains type valves, with their isolated
On the high tension front, numerous
voltages are provided for screen grid valves and several tappings
for different HT levels.
This example has had some modificatiuons
made. You can see a stud diode, a variable resistor and lots
of capacitors which look like they're from the 1960s.
The red/black mains lead dates
from the same era.
Serial number 103885
The Ekco DC15/25
click picture to see large
As DC mains were quite common
before WWII, Ekco included a DC model in their range. Because
of the vagaries of current and voltage (as explained in Ohms
law) there's a tapping under the unit for running at either 15
or 25mA (The designation for milliamps loosely inscribed as "MA")
Tappings for screen grid and
HT are provided, as the with the AC units, by sockets and a jumper
on the centre panel.
This example has been refurbished
by its last owner and finished in a matt black paint. Originally
it would have had a shiny bronzed finish.
Serial number 215432
manufactured by Ekco was the TC1 accumulator trickle charger for 2, 4 and 6
Click picture to see more
This is an accumulator charger,
dating from around 1929 or maybe a little earlier and is the
precursor of the later TC1
This early model is in the same
range of products as the boxier looking models shown here
Exide High Tension and Low Tension Charger, Type
AC64 S/No 1280
Click picture to see more
This old unit probably dates
to the early 30's and could charge an accumulator and also supply
HT for a battery operated radio.It used a metal rectifier for
Safety-wise the newer units
complied loosely with new IEE regulations in force in 1931. These
called for a number of recommendations, for which the units only
comply if the user follows the instructions in the booklet.
Earthing the case is done via
a wire to a terminal provided on the underneath of the chassis.
Most people would use two-wire mains cable, often connected to
a light socket via an adaptor. An external earth wire would have
to be carried from the receiver to a suitable earth connection.
There is no fuse included in
the unit although the regulations called for two fuses, one in
each side of the feed to the unit. Ekco got round this by advising
the user that such fuses were to be found at their mains distribution
board and if this wasn't the case then they were advised to fit
a couple of 3-amp types.
Headphones and loudspeakers
used on the radio being powered by a mains eliminator had to
be connected through a double-wound transformer and customers
were advised to procure one from their radio dealer. No doubt
many users were surprised by tingling sensations as they adjusted
I would imagine that in many
cases none of the above recommendations would be followed. Nowadays
the manufacturer has to ensure that his equipment is foolproof,
leaving no latitude for the end user to ignore safety.
An interesting quote from a
1938 publication by Westinghouse..
"It is essential
to use a mains transformer in all cases where a rectifier is
used in the voltage doubler circuit, in order to ensure that
the receiver circuit is isolated from the supply mains. If a
transformer in not used, there is a possibility of the "live"
side of the supply becoming earthed through the receiver earth,
with consequent damage to the receiver and rectifier".
No mention of electrocution
if the receiver is not actually earthed.