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VINTAGE RADIO
By JOHN HILL
Old Henry: one of my favorites
This month, I thought I would describe in detail
one of my favorite old radio receivers. This
nameless console model is of about 1933 vintage, is
huge in size and is so ugly that the designer must
have been totally inartistic. However, it performs
very well for an old timer and is one of my most
valued possessions.
My nameless set isn't really
nameless - I call it Henry. This
often prompts a question as to why
not Henrietta? My standard reply is
that no woman could be so
shapeless - it just has to be Henry!
Henry is all square corners and
sharp edges with short thick legs.
One could never think of such a
form as "she".
There seems little doubt (in my
mind anyway) that as far as early
radio was concerned, big was
beautiful! Henry fits this description fairly well for nearly everything about him is big.
But while the cabinet is quite
large and the chassis enormous, the
dial goes in the opposite direction
and is but a tiny circular spot on the
front panel. In fact, the dial is
greatly out of proportion to the
The all-aluminium chassis is an impressive sight to say the least. The aerial,
oscillator and IF coils are housed in unpainted aluminium cans while the four
valve shields are of polished aluminium. They don't make radios like this
anymore.
28
SILICON CHIP
overall bulk of the set but that was
pretty much the norm for the early
1930s.
Another thing that looks out of
proportion is the size and spacing of
the three control knobs. They are so
close together there's hardly room
for fingers. It seems so pointless
when there is so much room to
spread them out.
The circuitry
On the other hand, from an electronics point of view, Henry was
ahead of his time. The circuit is
unusual in many respects and differs considerably to what I consider normal. It is these differences
I wish to discuss in this particular
story.
The power transformers and
high tension chokes are worthy of
note for old Henry has two of each.
The larger of the two transformers
is mounted on top of the chassis and
is a huge affair enclosed in a pressed steel case. This "Clock" brand
transformer is strictly for the high
tension supply and provides the
rectifier valve (an 80) with high
voltage for its anodes and 5V for its
filaments.
After the rectifier, the high tension DC is passed through a 30
Henries (no relation) choke to
smooth out the ripple. This choke is
in addition to the usual speaker
field coil. As might be expected,
when both chokes are combined
with a couple of electrolytics, there
is absolutely no mains hum in the
loudspeaker.
The rectifier socket is of the old
1920's style and sits on top of the
chassis. Its external connections
are not only bare but quite accessible to probing fingers. Receiving a
The large high tension transformer (right) and the 30 Henry choke are
mounted side-by-side at one end of the chassis. The transformer's job is to
provide the necessary voltages to the rectifier valve (an 80) for the high
tension supply.
Henry's cabinet is hardly a thing of
great beauty but is pretty much the
norm for the early 1930s. The cabinet
stands 42 inches (that's over 1 metre)
high.
The rectifier socket (with bare
connections) is mounted on top of the
chassis. The small globe connects the
transformer centre tap to earth.
Bare external terminals with a potential exceeding 300 volts DC protrude from
the side of the 30 Henry choke. Don't touch - they can deliver an almighty
wallop!
high voltage boot from the rectifier
socket is as easy as poking a finger
onto the hot connections.
There are other nasties beside
the rectifier socket. The chassis
mounted choke is also connected into the circuit with bare external
terminals. These terminals are at
the rear of the set and are so positioned that 300 volts plus is well
within reach if one wished to check
the high tension with a finger. One
slightly incinerated hand would
certainly mean that there's nothing
wrong with the HT!
While we're on the subject of all
these electrical booby traps, I
should also mention that one of the
power transformer's three primary
taps (the one not connected to the
mains) was just tied up in a knot
with the bare wire protruding. This
didn't appeal to me very much so 1
taped it up.
The foregoing should be sufficient warning about the hazards of
tinkering around with old radios.
Some of the early manufacturers
made very little effort (none at all
really) to insulate dangerous
voltages from the user or serviceman as the case may be;
Even so, I don't consider the set
to be particularly dangerous, but I
do treat it with the respect it
deserves. I guess it's a bit like playing Russian Roulette, but in this
JULY 1989
29
The small dial and the closeness of the controls are out of proportion to the
overall bulk of the set but pretty much the norm for the 1930s. In fact, the
controls are so close that there's barely enough room for one's fingers.
case the player knows which
chamber the cartridge is in. That
makes the odds a good deal better.
The second power transformer is
about half the size of the main
transformer and is mounted under
the chassis. This smaller unit has
only one secondary winding of 2.5
volts and naturally supplies the
heaters of the other valves.
Both the transformers and the
chassis mounted choke are particularly large and heavy and are
more than adequate for the job. An
hour's use will see the 2.5 volt
transformer rise in temperature to
slightly warm, while the main
transformer and the high tension
choke remain cold.
Parallel pentodes
Another unusual aspect of this
particular radio is its output stage
which consists of two 59 pentodes
in parallel. That's right - parallel,
not push-pull!
These two valves are connected
grid to grid, anode to anode etc and
work in parallel. Withdrawing
either of the output valves has no
The output stage uses two 59 power pentodes in parallel for increased audio
output. Withdrawing either of the output valves has no affect on the set's
operation apart from a slight drop in volume.
30
SILICON CHIP
affect on the operation of the
receiver apart from a slight drop in
volume.
The old 2.5 volt 59 is an unusual
pentode in that the suppressor grid
is lead out to a separate base pin. In
any normal pentode the grid is earthed internally through the cathode. Such a set up gives the 59 an
additional base connection and also
allows it to be referred to as a "triple grid" valve. How the three grids
are connected is entirely up to the
set's designer.
Another different aspect of the
59 is that it has two separate
heaters with two separate cathodes. This type of construction is
almost exclusive to the 59 valve.
Most other AC valves have cylindrical anodes surrounding a single
central cathode.
I'm quite keen on the 59's odd
construction characteristic because a valve with one blown
heater will still work reasonably
well on the remaining cathode.
Henry has one such valve and it
tests at 75%. Even with the socalled good valve removed, the set
will still function on the remaining
59 with its blown heater.
At one stage I was inclined to
scrap this half defunct valve, but it
can stay in service for a while
yet. There is every chance that it
will keep on going for years.
The other valves are also of the
2.5 volt variety and include the fairly common types of 5 7, 58 and 2A6.
The 2A6 is a duo diode triode which
will immediately suggest to many
readers that the set has AVC
(automatic volume control) or, to
use the more correct term, AGC
(automatic gain control).
Henry's AGC is of the delayed
type and the delay can be noticed
when one crashes onto a particularly strong station. The sound
is momentarily louder before the
volume adjusts itself.
·
The set has no tone control but
the circuit is such that it produces a
particularly mellow sound and
there really is little need for an additional tone control. Whilst on the
subject of controls, Henry is equipped with an on/off switch which is
fairly unusual for a radio of that
vintage.
The chassis itself with its attach-
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Old Henry is truly a gutless wonder. Note the small power transformer on the
left. This supplies 2.5V AC for the valve heaters.
ed cans and valve shields is also
worth a mention because everything is made of aluminium. Both
the aerial and oscillator coils and
the IF transformers are all housed
in unpainted aluminium cans, while
the four valve shields are of polished aluminium.
Small dial
With all this hardware, the
chassis is an impressive sight when
laid out on the work bench. Unfortunately, the effect is spoilt by the
small and somewhat unimpressive
dial but I guess that that was the
way they made them back in the
early 1930s.
The miserable looking dial unit
drives the biggest 3-gang tuning
capacitor I have seen. The tuner
has built in mica trimmers on each
gang and these are conveniently
placed on top for easy access.
Henry, like many other vintage
radios of the early superhet era,
has an intermediate frequency of
175kHz. While this frequency may
sound strange by modern standards
(455kHz), it was common in Henry's
day.
Up-ending the chassis is a bit of a
struggle due to the weight of the
transformer and choke at one end.
However, once up-ended, the
underneath view is somewhat
disappointing. There is so much
space for so few components it
looks as though someone has left
out most of the parts. This,
however, is only an illusion for
everything that should be there is
there, even if it looks a bit to the
contrary.
The tapped, wirewound voltage
dropping resistor and the large size
of the one watt carbon resistors are
about all one could comment on as
far as the under-chassis parts are
concerned. It looks pretty untidy
really, due to the point-to-point wiring technique employed.
Henry is fitted with a 10-inch Jenson electrodynamic loudspeaker
and this functions reasonably well
for its age. Undoubtedly a more
modern speaker would sound a little better but Henry is one set that I
want to keep original. The fact of
the matter is that the original
Jensen speaker really does work OK
and produces quite a good sound.
In many ways, old Henry is a bit
of a strange beast. But as I said
earlier, he's one of my favorites.
Really, he's quite outstanding in
a number of ways. He is the only
receiver in my collection with seven
valves, the only one with a twin output stage and the only one with an
aluminium chassis. Henry is also
the largest set I have and possibly
the most horrible to look at. But he
does perform well and for only $40
I reckon he was a bit of a bargain
as well.
Perhaps at some other time in the
future I will write about another of
my favorites, but not many could
hold a candle to old Henry.
i!tl
HYCAL
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JULY 1989
31
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