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!