Presto

January, 1932
PRESTO-TIMES
16
MANUFACTURING TO INSURE
HIGH QUALITY
By Ross D. Siragusa, President Transformer Cor-
poration
There is no doubt about it—the industry is vitally
interested in mantel radios. There is nothing essen-
tially new in these sets, but we all admit they are
different. They brought new problems to the radio
dealer, distributor and manufacturer, and when some-
thing different is placed on the market, it is interest-
ing to go over the pros and cons.
The subject has been discussed extensively in print
from a merchandising angle and a few words as to
their manufacture should be appropriate.
Design
The design problems with a mantel type radio are
primarily those of building high quality apparatus at
reasonably low prices in which the utmost in quality
is obtained, both as to the components which go to
make up the set, and the performance of the finished
product.
We have always had inexpensive radio receivers,
but the quality has generally been in accordance with
the price. This season saw a public demand for a
receiver in the low price class, of high quality manu-
facture, of lesser range and power than the larger
receivers but equal quality as to those results which
are obtained.
One example of the problems confronting the de-
sign engineer of the mantel type set, might be cited
in tone quality baffle limits.
It is generally understood for true reproduction
of loud tones, a large baffle is required. This baffle
is supplied in the larger sets by the physical dimen-
sions of the cabinet. -
-
With-a mantel type set, the size of 4he cabinet is
necessarily limited, and of course, so is the baffle
dimensions in the chassis and loudspeaker. This
means that if the present mantel type set were assem-
bled into a larger cabinet, low tones might predom-
inate.
While the public might be pleased to pay one-half
the price of a large set for a mantel type receiver,
they would be pleased to operate that set if it brought
in only half the stations. This, in itself, necessitates
high gain per stage and the higher gain necessary is
obtained by many manufacturers in increasing the
ratio between the tuning condenser for a particular
stage and the r. f. coil for that stage, and is unusually
brought about by a decrease in the capacity of the
condenser tuning that stage.
Theoretically, this answers the purpose, but unfor-
tunately, a good receiver that the public will buy, is
seldom produced entirely on paper in the matter of
its design. For example, if the capacity of the tuning
condenser we have mentioned is decreased, it means
that such capacity as is left in the condenser must
be worked within closer tolerance than would be
the case with the larger condenser.
A uniform sensitivity over the tunable range is de-
sirable in any receiver, fortunately, is more easily
obtained in the mantel type radio than in its big
brother. Amplification of stations operating on high
or low wave lengths is assured in equal degree by
means of compensation. In the r. f. coils, compen-
sation is simpler by virtue of fewer tuned stages,
thereby having less to compensate for. It would be
safe to say that 75 per cent of design problems with
mantel type radios are brought about by very com-
pact assembly; for example, ventilation holes m the
chassis are desirable whereas, in a large set, with
greater space for heat radiation, they would be un-
necessary. The field coil of the dynamic speaker has
openings diametrically opposite, to permit air circu-
lation, and it is good practice to leave one side of the
power transformer unshielded for the same purpose.
It is necessary, of course, that the unshielded side of
the transformer carry only low voltage leads.
THE MIDGET AT LOW SALE PRICE
It would be well to clarify this point by explain-
ing that no one manufactures a perfect anything, and
this is particularly true when we are dealing with
such apparatus as radio variable condensers. They
are manufactured with a certain capacity intended for
each stage. When the condenser is finally assembled,
it will be found that each stage in the variable con-
denser gang departs slightly from the ideal value by
being either greater or smaller in capacity. Radio
reproduction engineers set a limit to the amount by
which any condenser may depart from the ideal value
and term this a plus or minus tolerance.
To give the reader some idea of how closely these
tolerances are held, it might be interesting to know
I
A BATTERY OK SEMI-AUTOMATIC COIL WINDING
MACHIXES AKK CONSTANTLY BUSY WINDING T H B
COILS USED IN CLARION RECEIVERS.
HERE IS SHOWN THE ASSEMBLY OK FIXED
CONDENSERS IN THE TCA PLANT.
T is a pleasure to ex-
press our thanks and
appreciation for the
loyal support of those
music houses who have
applauded our efforts to
IN THESE GIANT VAULT-TANKS THE FIXED CON-
DENSERS ARE BAKED UNTIL ALL EXPOSURE IS
REMOVED, THEN IMPREGNATED WITH HALO WAX
AND FINALLY IMMERSED IN OIL.
New
1932 models soon
to be announced.
give them the utmost in
grand piano values.
Look out for these.
All compliments of the
They will be money
season and best wishes,
makers.
B. K. SETTERGREN C O .
Bluffton, Indiana
HERE ARE SHOWN SOME OF THE PUNCH PRESSES
IN THE TCA PLANT WHTCH STAMP OUT PARTS
SUCH AS TRANSFORMER LAMINATIONS, TUBE
SHIELDS, POWER PACK CASES, ETC.
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