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The Zenith model 9S367 (9-S-367) from 1939 was a my first (to
date) Zenith shutterdial set. It is a 9-tube AC superhet circuit
console.
It receives the standard broadcast band and two short wave bands, has
"automatic" or push-button tuning, and the Zenith Radiorgan
tone control The radio worked (at least it powered up and made noise) when received. It was later discovered that the radio was almost 100% original - almost no prior servicing had been done. I decided to try and maintain the original top and bottom chassis appearance and to reverse previous repairs to the extent possible. The schematic for the Zenith 9S367 can be found on Nostalgia Air. Any part numbers mentioned will refer to numbers on that schematic. |
My antique radio restoration logs
Only the 6U5 eye tube was branded Zenith. It was very weak, and likely the original tube. All the other tubes had been replaced.
R12 (220K) had been replaced.
R17 (10K) had been replaced (remnants of the burned original remained).
C12 (oscillator circuit) had one lead cut - it had likely shorted and burned R17.
My usual restoration procedure is to first make a complete survey of the condition of all components. The survey results guide my restoration strategy. If major and unique components are defective or missing and cannot be restored or replaced, I may elect to sell the radio rather than restore it. I always assume that all paper and electrolytic capacitors are leaky and thus should be replaced (I always "restuff" the original containers if possible). Any mica capacitors are assumed OK until testing proves otherwise. Since the radio actually worked, no extensive survey was needed, as major components were OK.
All tubes and shields were removed. The automatic tuning unit was removed. The dial scale and pointer were removed. The shutterdial mechanism and bandswitch link was removed. The dial drive and volume control shafts, flywheel, and associated hardware were removed for cleaning and for access to components below. The tuning capacitor was removed for replacement of grommets and for cleaning. The top of the chassis was cleaned with GoJo hand cleaner and 00 steel wool.
I then took photos of the chassis bottom so that routing of wiring and component placement can be restored. Lead dress is often critical in radios. When I replace a component, I always remove the original part completely from a terminal. Other components connected at the terminal are protected from heat using old medical clamps. Excess solder is then removed using a solder sucker in order to expose terminal holes for reattachment of the rebuilt or replaced component.
The volume control switch was flooded with Big Bath cleaner and cycled many times. The switch eventually worked. The automatic tuning contact springs were cleaned with lacquer thinner on a pipe cleaner followed by DeOxit and then more lacquer thinner and a pipe cleaner.
The tuning capacitor grommets were replaced by modern rubber grommets. The tuning capacitor was cleaned in an ultrasonic cleaner followed by soap, water, and toothbrushes. The bearings were then relubed using lithium grease. The reduction gears and anti-backlash assembly was disassembled, cleaned, and relubed.
The volume control and tuning shafts were cleaned and relubed. The missing dial drive belt was replaced using round rubber replacement stock, cut on a 45 degree angle, and glued using super glue.
One shutterdial return spring was missing, which resulted in one shutter not returning or returning slowly. There were original springs still in place for comparison. The spring had a long straight end with a hook that connected to the shutter. I found a spring in my spring collection that was about the same length and strength. I fabricated the long hooked end using a piece of buss wire. The shutter assembly then worked correctly.
The tip of one of the Radiorgan tone control switches was broken off. Replacement switches are available from Alan Jesperson, but they are not the same color as the originals. I had a good, complete and unbroken Radiorgan tone control unit salvaged from my 7S342 parts chassis. But there was a problem: on the original radio, all the Radiorgan controls, as well as the On, Off, and automatic tuning station selector switches faced DOWN. On the 7S342 switch assembly, the top row faced UP and the bottom row faced DOWN. I did some research and looked at several photos of the 9S367 on-line. I found that there were examples of BOTH types! I contacted Alan Jesperson (a Zenith expert!) who said that on early units, all switches faced DOWN. But customer complained that there was not really enough spaced between the rows to pull the upper switches if one had fat fingers! This resulted in broken switches. So Zenith changed the setup to the alternating up/down arrangement. So I could legitimately setup my radio with the top row facing up and the bottom row facing down. Only the Radiorgan switches are fixed. The ON, OFF, and Station select switches can be installed either way. So I was able to use the 7S342 switch assembly to repair my radio. I did rewire the switch assembly to match my original switch assembly.
The missing tone tabs and stations ID tabs were replaced using modern reproductions from Alan Jesperson. Unfortunately, the color is not the same as the original tone control and stations selector buttons. Also, the reproduction tabs tend to fall out! After some questions on Antique Radio Forums, the tabs were secured using a small dab of silicon adhesive (they can be removed if needed).
All original Zenith paper capacitors were rebuilt in their original cases using modern 630 volt axial film capacitors in order to maintain the original under-chassis appearance. I reseal the cardboard tubes using rosin salvaged from RCA catacombs (it melts at a low temperature and will not damage the replacement capacitors).
The filter capacitor C25-C26 (10+5mfd/450 volts FP type) was replaced by a 10+10mfd/450 volt NOS capacitor (reformed) from my stocks. C27-C28 (15mfd/450 volts +10mfd/250 volts FP type) was replaced by a new manufacture 20+20mfd/450 volt available from Antique Electronic Supply.
The two dogbone resistors that were out of tolerance were replaced by a NOS dogbone resistor (that was in tolerance) and another that had drifted to near the correct value. That one was repainted using hobby paint to the correct color codes. While this resistor may continue to drift, so will the others in the set. I wished to maintain the original above and below chassis appearance. The remainder of the resistors that needed replacement were standard 1/2 watt carbon composition types.
Correct G type tubes were installed for the 6F5G, two 6K7Gs, and 5Y4G, and correct Zenith tube shields were installed. A usable 6U5 eye tube was installed. The two 6J5G tubes were swapped. One was slightly weak and one good. The good one was installed as the oscillator, and the slightly weak one as the second detector.
Once the radio was reassembled and the tubes installed, power was brought up slowly using a variac. AC power consumption was monitored using a watt meter, and a DVM monitored the B+. The radio came alive immediately and worked.
The set was then aligned - no surprises. The broadcast band peaked up nicely. The push buttons were adjusted to local stations.
The radio performs well, and has very good tone on the broadcast band.
