Refurbishment of a Zenith G500 Transoceanic – Gerry O’Hara
I have repaired, refurbished and restored several Zenith Transoceanic (‘TO’) tube radios over the years.
These radios are ubiquitous over North America as hundreds of thousands were sold from the 1940’s
through the early-1960’s, when solid-state TOs, introduced in late-1957, took over this segment of the
domestic market for Zenith until it was effectively killed off by foreign imports, especially from Japan, in
the 1970’s.
The earliest TO-like
radio was introduced
in 1941 - the
Broadcast band only
(Model 5G500), using
Octal base tubes. This
were replaced by the
first real TO, that
included the
shortwave broadcast
bands (Model 7G605)
in 1942 (‘Clipper’ and
‘Bomber’ versions),
and then the post-
WWII Model 8G005Y,
both using Loktal base
tubes. The next ‘big
leap’ occurred with
the replacement of
the Loktal tubes with
miniature tubes and
the replacement of
the rectifier tube with
a selenium rectifier in the Model G500, introduced in late-
1949. This design set the scene for the basic TO architecture
for the next decade, with the subsequent models (H500,
L600, R600, T600, Y600, A600 and, finally, the B600)
comprising mainly cosmetic and electronic tweaks to the
G500, eg. slide rule dial (L600 onwards), frequency
coverage, various detail circuit amendments, push-switch
dial lamp, retractable line cord and the like, with the
production of the B600 finally ceasing in 1962. The G500
was only manufactured for a couple of years (90,000
produced), and is considered by some as a ‘transition’ model
to the ‘true’ TO’s of the 1950’s, but I think it is more than a
transition model: it is the ‘building block’ on which all
subsequent TO models were built around.
Zenith G500 Transoceanic Refurbishment Gerry O’Hara
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Initial Inspection
I was given a G500 to refurbish for a
friend recently: it was a little ‘tatty’
(photos of front and back on page 1
and right), but I have seen, and
worked on, much worse examples.
It was reasonably clean and
complete, and lacked that
damp/musty smell that screams
that the set had spent years in a
damp shed or garage. Cosmetically,
some of the ‘stag’ covering was torn
and missing from the corners and
edges (photo, below left), the
lettering had faded from the push-
buttons, and the dial was badly
scored by a pointer that had been
pushed hard against the dial at some point and made contact with it at several points in its rotation
around the dial (photo, below right). Electronically, it had
several of its ‘bumblebee’ caps replaced by brown plastic-
cased paper caps and, unusually, a few resistors replaced.
I did not test it before electronic refurbishment.
Electronic Refurbishment
Refurbishment of a TO’s electronics is fairly straightforward: in this chassis, designated ‘5G40’, there are
14 paper capacitors and five electrolytics to replace. Re-stuffing ‘bumblebees’ can be done, eg. see
article on this here, however, for this chassis re-stuffing was not required by the owner. The
replacement electrolytics were installed under the chassis – there is plenty of room if care is taken, using
Zenith G500 Transoceanic Refurbishment Gerry O’Hara
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a tag strip soldered to one of the chassis tags of the original multi-electrolytic (all sections of this were
disconnected, but the capacitor left in place for above-chassis aesthetics). If any of the resistors need to
be replaced, the small size and shape of the originals makes reproducing them to look like the originals
very difficult, so there is little point in the capacitors looking original if several of the resistors do not.
Most resistors can be checked in-circuit providing the tubes are pulled first, and I find that there are
usually a few that are no longer within tolerance (though the set will likely work just fine like this). In
this chassis I replaced three of the original resistors plus one of the previously replaced ones, so four in
total.
The selenium rectifier was replaced with a silicon rectifier (1N4007) and its series resistor (a 130 Ohms,
3W part) replaced with a new 220 Ohm 5W part to bring the HT voltage back to spec. (silicon rectifiers
are more efficient and exhibit lower voltage drop). The photo above shows the under-chassis before the
refurbishment work and the one below after.
The tubes were tested for emission and all were ok except for one of the 1U4 tubes, which I replaced
with one that tested good.
The tuning gang was cleaned and lubricated, and its rotor finger contacts cleaned with Deoxit, as was
the volume pot which had been a little crackly when I carried out a function test after the recap. The
Zenith G500 Transoceanic Refurbishment Gerry O’Hara
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coil stack and tone control slide switched were given a thorough clean and all switch contacts cleaned
using Deoxit.
Testing and Re-alignment
I undertook a full IF and RF re-alignment: the IF was quite a way off-tune, and peaking the IF transformer
slugs made a significant improvement in gain. The RF stages were reasonably well on tune and only
slight tweaking was needed on all but the 49M band, where the antenna slug had been screwed tightly
into its former – this took some coaxing out to allow it to be tuned correctly. The RF alignment was
undertaken with the chassis temporarily re-installed in the cabinet as this can make a difference to the
RF alignment, as can the presence of the battery pack (see below).
Mechanical and Cosmetic Refurbishment
The chassis was again removed from the cabinet so
the I could start work on the cabinet’s cosmetics.
While doing this I noticed that the speaker mounting
bracket was wobbly. This was due to the rubber
mounting grommets being perished. These were
replaced with new (neoprene) grommets and the
speaker was now properly secured to the chassis
(photo, right).
The black ‘stag’ material covering the plywood
cabinet had many scuffs, small tears, nicks and
some parts were worn off entirely – two on the
bottom corners and more along a couple of the
edges. It also had numerous white paint spots
that had to be gently coaxed off.
Prior to starting work on the cabinet, all metal
parts, handle and ‘Wavemagnet’ antenna were
removed. The nicks, tears and missing pieces
of stag material were then repaired by removing some
of the same stag material from the overlap areas inside
the cabinet using a scalpel, trimming the areas to be
repaired and gluing suitably-shaped pieces of the stag
material into these areas (photo, above). The edges of
the repairs were then feathered-in using fine sandpaper.
The material was then re-finished using a coat of black
shoe dye, this being allowed to dry and then buffed over
with a cloth before polishing with a couple of coats of
‘Armor All’ (Original formula).
Zenith G500 Transoceanic Refurbishment Gerry O’Hara
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The dial cover was cleaned with Novus #1
(anti-static plastic polish), and the openings
for the volume pot shaft and tuning shaft
trimmed slightly to avoid binding on the
shafts when the chassis is re-installed - I
think the plastic dial covers warp/shrink
slightly with age as I have encountered this
binding on several other TO’s.
Screw heads were re-blacked using a black
permanent marker pen. The same pen was
used to touch-up the scored dial (photo,
right).
The knobs and push-buttons were washed
in soapy water and polished using Novus #1
and #2, and the lettering on the push
buttons renewed with white acrylic paint.
The rod (whip) antenna was in reasonable condition, with the chrome finish largely intact. It had at
some point received a liberal dose of oil and this may be why it was rust-free – the oil was cleaned off
and the rod polished with ‘Autosol’ cleaner. The
same cleaner was used to clean the metal cabinet
fittings before they were re-fitted to the cabinet.
The handle, ‘Wavemagnet’ antenna and
connecting wires were cleaned with Novus #1 and
#2, and the antenna connections with Deoxit, and
these were then refitted into the cabinet.
The band change buttons and the chassis were
then installed into the cabinet, the knobs pushed
into place, followed by fitting the rod antenna and
small wood block securing the coil stack.
Battery Pack
Although the battery compartment makes for a
handy storage cubby, it looks much better if there
is a battery pack of the correct type installed. Of
course these are ‘unobtanium’ these days, except
from some specialist suppliers that hand-fabricate
them. However, they can be made from scratch
with some effort and skill. Luckily one of my
friends had a spare one he had fabricated that the
set’s owner decided to purchase (photo, left). The
owner decided that he only wanted the battery
Zenith G500 Transoceanic Refurbishment Gerry O’Hara
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pack for cosmetic purposes and would not install batteries, so there was no need to tweak the RF
alignment with the battery pack (case only) installed.
Closure
The G500 performs very well, and this model set the standard for tube portables for the next decade –
other manufacturers mimicked the design concept, eg. the Hallicrafters ‘Trans-World’ series and RCA’s
‘Strato-World’ models, but somehow they never achieved the same ‘cache’ as those sets that had the
famous ‘Transoceanic’ moniker (I must admit, that name is still cool!).
I think the TO’s with the ‘airplane’ dial, as sported by the G500, were the best-looking and, arguably, the
G500, with the gold Zenith badge on the Wavemagnet antenna is the best-looking of all. Of course this
refurbishment only provides a glimpse of what one of these sets must have looked like when new and
just out of the box – now that would have been a very special moment for a new owner in 1949!