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VINTAGE RADIO
By JOHN HILL
A pair of Astor valve radios
Occasionally, I get to repair vintage radios
for other people and that’s what this month’s
column is all about. It concerns a couple of
interesting old Astors.
Noel, a new collector of my acquaintance, phoned me recently with
a problem. He had found a couple of
receivers in a local antique shop and
wanted my advice before buying them.
As both were priced at $75, I conjured
up a mental picture of a couple of
cracked Little Nippers with missing
knobs or something equally undesirable. $75 doesn’t buy much from an
antique dealer!
To my surprise, the radios were by
no means cracked Little Nippers but a
genuine 1940 Astor “Mickey Mouse”
and an early post war Baby Astor. The
latter is known to collectors as an Astor Football. Both are very collectible
items!
My first thought was one of annoyance that I had missed out on
two good radios, neither of which
was in my collection. But, on second
thoughts, I considered it better for
Noel to have them because I would
A 1940 BP model Astor “Mickey Mouse”. Although a very collectible item, it is
a fairly awkward receiver to work on and has no really outstanding features
apart from being very compact. No, the knobs are not the originals!
88 Silicon Chip
still get the job of repairing them and,
with a bit of luck, a Vintage Radio
story as well. That would keep us
both happy.
After a bit of bartering, the Baby
Astor was dropped to $50 and I took
both receivers home to see if Noel had
bought himself a good deal.
Fixing Mickey
The “Mickey Mouse” was the first
to be repaired. It was quite dead and
gave no response whatsoever, although
the valves lit up, which always gives
a little hope.
A closer inspection revealed that
the output transformer was open circuit and that someone had previously
disconnected the electrodynamic
loudspeaker and then mixed up the
leads when reconnecting it. The original 6Q7 detector/first audio valve had
also been replaced with a 6SQ7 which
is just about the same valve except that
it is a single-ended type and lacks a
top cap connection.
Unfortunately, those characteristic
“Mickey Mouse” control knobs were
missing. Apart from that, the rest of
the set looked fairly original.
Now while these so-called collectible radios are eagerly sought after,
those who repair them often see them
in a different light. This particular
“Mickey” is not what one would de
scribe as easily worked on and it has
a few undesirable features.
In its original form, the bulk of paper capacitors underneath the chassis
makes it impossible to gain access to
the valve sockets, to check voltages,
etc. This situation improves greatly
once the old capacitors have been
replaced with smaller, modern types.
Removal of the loudspeaker requires
the dial, dial cord and the dial light to
be either removed or disconnected, as
If it wasn’t for the “Mickey Mouse”
aspect of these radios they would be
just another old radio. Astor used the
Disney name without permission and
later dropped the “Mouse” bit. The
Astor “Mickey” was a very popular
post-war receiver.
is appropriate. And finally, fitting a
new speaker grille cloth is fairly tricky
due to the fact that the dial is in the
centre of the speaker opening.
All things considered, the Astor
“Mickey Mouse” is not the most convenient valve receiver to work on –especially when doing a full restoration,
as there are so many things that need
attention.
Apart from being a very small radio
(hence the name, “Mickey Mouse”)
there is nothing really outstanding
about this particular model at all.
The court wrangle with Disney over
the unauthorised use of the name is
what makes the set collectible. As far
as the receiver is concerned – it’s only
average!
After doing everything that needed
doing, it was tryout time. The set burst
into life and there was that feeling of
relief knowing that all the checking,
replacing, and repairing had finally
produced a positive result. But that
feeling of relief was short-lived because, 30 seconds later, the sound had
faded to nothing.
So many restorations have some
strange little quirk to them that hasn’t
been encountered before. In this case,
none of the parts overheated and there
were no crackles or hum. In fact, there
was nothing obvious at all – just a
volume fade off to nothing.
Although the valves tested OK, I
have learnt not to rely completely
on any valve simply on the basis of
This close-up shows the dial and speaker opening. Having the dial in the centre
of the loudspeaker makes a new grille cloth rather difficult to fit. Note the hole
in the dial (at 12 o’clock) where the dial lamp has “burnt” through the celluloid.
The Astor “Mickey” required several component replacements before it worked
satisfactorily. Some of the old resistors had tripled in value.
an emission test. This test does not
check a valve for all working functions
and other faults can be overlooked.
A replacement 6A8 sorted out this
particular problem but it took a while
to locate.
(Never overlook the limitations of
an emission tester. It does just that;
it tests a valve’s emission – nothing
more. Since the emission eventually
fails in any valve, it is a most logical
test to make. But that’s to say that this
is the only manner in which a valve
can fail; there are a whole range of
possibilities other than that of emission failure. Ed.)
Noel was pleased that the tattered
grille cloth was replaced with a piece
of original material obtained from
an old console cabinet. There were a
couple of good corners in this piece of
cloth and having the right fabric in a
collectible receiver such as a “Mickey
Mouse” really sets it apart.
From a performance point of view,
the 5-valve “Mickey Mouse” was only
average and any of Astor’s post-war
5-valve receivers would outperform
it by a fair margin.
One man & a baby
The second set, the model GR Baby
Astor was next and as this little receiver was in “working order” the job was
November 1996 89
ing the grid bias on the variable Mu
control grid of the 6G8G. So the 6G8G
performs quite a few functions.
Despite the clever circuit, the Baby
Astor needs a good aerial if it is to
give any worthwhile performance.
Even then it is basically a local station receiver and if a station is too
close it can give rise to a fair amount
of interference. The little Astor is not
very selective.
Parts replacement
The 1948 GR model Baby Astor was known to collectors as the Astor “Football”.
It is a 3-valve reflexed TRF receiver of fairly limited performance.
started knowing that it should be fairly
straightforward. Even so, the Astor
required quite a few hours of work to
complete the restoration.
On removing the chassis from the
cabinet it was surprising to see that it
was not a superhet but a simple 3-valve
TRF (tuned radio frequency) receiver.
The valves used are: 6G8G, 6V6GT and
a 5Y3 rectifier.
There is some trick circuitry in-
volved in the little Astor, which is a
reflexed TRF receiver. In a reflexed
receiver, one particular valve performs
a dual function, being used to amplify both radio frequency and audio
frequency signals simultaneously. In
the case of the Baby Astor, the 6G8G
valve does these two operations and
it detects the signal as well, using one
of its twin diodes.
The volume is controlled by vary-
This photo shows the rear view of Baby Astor chassis. The three valves are:
6G8G, 6V6GT and 5Y3 rectifier.
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Replacements were confined to the
usual components, mainly paper and
electrolytic capacitors
One thing that could not be replaced
was the strong odour of mouse urine
which was nearly overpowering when
ever any soldering was being done.
There are few things worse to work on
than a well-saturated chassis. It really
turns my stomach!
There is a small bracket at the front
of the chassis near the bottom of the
loudspeaker. Mouse activity had been
intense in this area and the bracket has
obviously been a popular spot for the
relieving of bladders. Unfortunately,
the overflow had seeped down onto
the edge of the speaker cone and had
rotted out some of the cone.
The speaker was repaired using
Silastic silicone rubber compound. In
fact, the whole outer rim of the cone
was reinforced as the edge had become
very thin and fragile.
These speaker repairs proved entirely satisfactory and the receiver
could not have sounded better had a
new speaker been fitted. It is amazing
the cone reconstructions that can be
done with a bit of perseverance. The
silicon rubber treatment may not look
very dainty but it is usually effective
and long lasting.
The reason for all the previously
mentioned mouse infestation was the
fact that the speaker grille cloth and,
presumably, the cardboard baffle to
which it was attached, was missing.
This gave front door entry to any
rodent wanting to call the little Astor
home.
A replacement grille cloth baffle
was made from cardboard and, once
again, covered with another corner of
the tattered console grille cloth so as
to look as though it was the original
fabric.
One big advantage of using old
speaker grille fabrics is that such a replacement doesn’t look too new and is
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cracking the dial at the stud holes.
As luck would have it, I had a broken cabinet with the dial and studs
intact. Transferring these components
to the good cabinet did much to improve the general appearance of the
receiver.
"Silastic” silicone rubber was used to reinforce the outer rim of the speaker
cone. It mightn’t look too neat but it certainly makes an effective and longlasting repair. The dial cord was difficult to re-string.
more in keeping with the odd scratch
or chip in the cabinet. A restoration
that incorporates a good secondhand
grille cloth has a very genuine appearance to it.
Dial problems
The dial cord nearly always needs
attention and this particular one was a
bit tedious to string. It is one of those
with a hole through the tuner control
shaft and as the cord unreels on one
side of the hole, it winds up on the
other. The right number of turns needs
to be on the shaft and it must also be
wound in the right direction before
success is possible.
Of course, the best thing to do with
tricky dial cords is to sketch the layout before unstringing the cord. But
when the cord has broken or, worse
still, is missing, one has to start from
scratch and work it out the hard way.
There are some incredibly difficult
dial cord setups in old receivers, with
some taking several metres of cord to
make the long journey around all the
pulleys, etc.
The dial was also a problem on the
little Astor Football. Originally the
acrylic dial strip was attached to the
cabinet by a couple of split studs that
just “thumb-push” into the cabinet.
These had fallen out and had been
replaced with countersunk screws
which had been over-tightened, thus
Alignment
There is not much to align when
tuning up a Baby Astor. You just
adjust two trimmers on the tuning
capacitor and that’s it! The performance is reasonable when the set
is connected to a good antenna and
sound quality is excellent for such
a small receiver. But without an antenna it is a dismal thing, to say the
least, although it would work OK in
a capital city situation with an indoor
aerial –and that’s what it was originally designed to do.
Radio receivers such as the “Mickey
Mouse” and the Astor “Baby” are very
collectible items today and Noel has
done well to pick up these radios.
Although Noel has only four valve
receivers at this stage, he is putting
together an interesting collection and
SC
is off to a good start.
November 1996 91
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