click image for a close-up of the dial
Zenith 12-S-267 (12S267) Shutter-Dial Floor Model Radio (1938)
Zenith 12-S-267 (1938)
The magnificent 12-tube Zenith 12-S-267 (12S267) console radio
from 1938 is a much coveted set that is an uncommon find today. It
had an original purchase price of $169.95 and boasts the following
impressive list of features:-

  • Motorized tuning & foreign station re-locator
  • 12-inch electrodynamic speaker with "acoustic adapter"
  • Push-pull 6V6 output stage producing a room-filling 15W
  • Three waveband tuning range (BC/SW1/SW2)
  • Robot (shutter) dial with tear-drop shaped escutcheon
  • Tell-Tale controls
  • Local/distant reception switch  
  • Tuned RF stage with triple filtering
  • 5-point tone control (voice/normal/Hi-Fi/Bass/Foreign)
  • Deluxe cabinet in exotic veneers
  • Tuning eye

The tube line-up is:-

  • 6K7G (tuned RF stage)
  • 6L7G (1st detector or mixer)
  • 6K7G (IF)
  • 6J5G (oscillator)
  • 6H6G (2nd detector/AVC)
  • 6J5G (1st AF)
  • 6J5G (2nd AF)
  • 6J5G (phase inverter)
  • 6V6G - 6V6G (push-pull output)
  • 6T5 (originally), now 6U5 (eye tube)
  • 5Y4G (rectifier)

Frequency coverage is 540-1752, 1740-5930 & 5490-18400kc.

Although the tone control offers a Hi-Fi setting, this is not achieved
through widening of the IF bandwidth - contrary to the approach
taken by Zenith's top-of-the-line Stratosphere models and also by
a number of Philco, RCA, Stromberg Carlson and other consoles
of the era. In fact, the RF/IF section of the 12S267, although
adequate, is rather conventional. Zenith instead focused on
producing a radio having great audio, outstanding cabinetry and
unrivalled ergonomics.

The loudspeaker is fitted with an
acoustic adapter, seen in the
photo below right. This is basically a "conical cover" that can be
slid towards the rear of the radio to increase bass response or
pushed inwards to dampen it. The claim was that it could compen-
sate the acoustical characteristics of any room. I must say that
unlike the gimmicky acoustic contrivances offered by many radios
of the era, this one turns out to be quite beneficial, as even a
modest repositioning of the adaptor produces a noticeable change
in bass reproduction. The 12S267 in fact produces the room-filling
"big sound" that Zenith is famous for and is certainly amongst the
best sounding Zeniths that I have encountered!

I found the graphic to the right embedded in an old newspaper
advertisement for 1938 Zenith radios. However, I'm clueless as to
whom the cartoon character may be! A 1938 robot? Store mascott?
chassis 1204 view
Acoustic Adapter
Restoration Notes
When I purchased this radio in early spring of 2006 it had been partially re-capped. However, upon getting it home I found the
performance somewhat disappointing. A cursory investigation revealed that one of the 6V6G output tubes was running cool and  I
soon found this to be the result of an open output transformer primary winding. I ordered a compatible replacement from
radiodaze
and installed it on the rear of the loudspeaker in place of the original. The radio sounded much better but I still felt that something
was missing, after all, I've heard so much praise heaped upon these big Zeniths for their sound quality.

So next I turned my attention to completing the re-capping that the previous owner had begun. The first thing I noticed was that
several of the replacement components had just been "tacked" into place using a small amount of solder and it did not take much
to pry them loose. I ended up replacing or re-soldering most of these. Unfortunately, the originals had been discarded and on
high-end sets such as this I generally like to re-stuff the carcasses with the new components so as to preserve the original
appearance. But so be it. However, I did re-stuff all remaining caps as well as replace a number of out of tolerance resistors.

A good 6E5 eye tube had been inserted by the seller but it was not opening or closing, so I installed a new 1Meg resistor in the
base of the tube's socket and that did the trick. While the socket was dis-assembled, I replaced the crumbling rubber-covered
wiring between it and the chassis. The 6E5 now functioned but it had a tendency to produce an overlapping pattern on strong
signals, so I replaced it with a new 6U5. The 6T5/6U5 tubes feature reduced sensitivity to eliminate this problem. The
schematic
calls out a 6T5 type, but these are now extremely rare. The 6T5 and 6U5 are electrically equivalent, though the 6T5 produces an
iris-like pattern compared with the 6U5 and 6E5 fan-shaped patterns. If I ever come across a good 6T5, perhaps I'll install it in this
radio!

When I first operated the set  following completion of recap, it would burst into a very loud, house rocking, low-frequency oscillation
when playing program material with any sort of low-frequency content at anything but the softest volume. At first I thought it was
acoustic feedback and indeed some of the audio tubes turned out to be overly micro phonic. However, the problem persisted when
these were replaced. After checking my component replacements and finding all to be fine, I compared the wiring
layout (dress)
against photos of an untouched original 1204 chassis that I saw on Ebay. I had taken chassis photos prior to commencing my work
but I wasn't sure to what extent the layout had been disturbed by the previous owner. Upon re-dressing the wiring & components in
the audio stages to match the original, the problem went away.  Just goes to show the importance of preserving the original layout
when replacing components in these radios with high-gain audio stages! The radio is now a great player and every bit lives up to
my expectations for a big Zenith.
Zenith...America's most copied radio ...again a year ahead.
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