Restoring the Zenith 7G605
Trans-Oceanic Clipper
![[Zenith 7G605]](images/7g605.jpg) |
©1997, Bill Harris
AUGUST 1995
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There is a flea market not far from my house on Mondays and Tuesdays each week. I usually try and get there early because if I don't the antique dealers and collectors tend to snap up any good radio bargains. This particular Tuesday I slept a bit late and had just about decided to blow it off, but I always enjoy looking around so I went anyway. I arrived so late I had to go all the way to the end of the parking area to find a parking spot. The only place left was in front of a truck that had also arrived late and the dealer was just unloading his wares. I walked around the corner of the truck just as he sat it down, a Zenith 7G605. I almost took it out of his hands, but I didn't want to look too anxious. I knelt down and examined the set. All the essential parts were there, Wavemagnet, knobs, Waverod, front door. It was missing the leather handle and there was no owners manual. The case was pretty dirty but no major dings or missing covering, and the chassis looked good. "How much for the old radio?", I asked. "Asking $75", was the reply. "Take $50?", I countered. The dealer countered my offer with $55. "Sold", said I.
I have been collecting Zenith T/O's for some time and managed to obtain all of the black suitcase style tube models but the 7G605. However due to the scarcity and price this first model was commanding among collectors, I had just about given up hope of owning one. Needless to say my day was made, and this was one time I was glad to be late to the flea market. I was anxious to start the restoration process which is documented here, but first a bit about the history of the Clipper.
![[Zenith Logo]](images/zenlogo.gif)
The story of the Trans-Oceanic began in 1939 when the president of Zenith, Commander Eugene F. McDonald, Jr, wanted a portable radio he could use on his trips to a remote fishing lodge in Canada.
After twenty prototypes and two and a half years of development effort, the Zenith engineering department produced a multi-band, portable receiver. McDonald took the receiver to Canada where he monitored short-wave broadcast from the United States and Europe.
Another of the prototypes went with explorer Admiral Donald B. MacMillan to the Arctic. Both MacMillan and McDonald were pleased with the sets performance. Production of the Zenith Trans-Ocean Clipper Deluxe Portable Radio began in late 1941.
The radio was equipped with six bands; Broadcast (AM), 49, 31, 25, 19, and 16 meters. The advertisement for the model 7G605 Clipper first appeared in January 1942, and promised the radio was "Coming - In a week or two."
The radio shown in the first ad had a sailboat design stitched into the grill cloth, perhaps because Commander McDonald was a boating enthusiasts. By the time the set actually hit the market in early 1942, the U.S. found itself in the middle of World War II. The sailboat was soon changed to a four engine bomber, as if to say that Zenith, like other major U. S. industries, had gone to war.
After producing 35,000 sets, Zenith had to cease production of consumer items to go into full war-time production. There was a backlog of over 100,000 orders for the Clipper when production ceased.
Many of these rugged little sets traveled with American GI's all over the world. Dozens of letters were written to the Zenith company by soldiers telling of the abuse the receivers had to take, but still continued to receive short-wave broadcast from the USA, which helped to ease the loneliness of being so far away from home.
The set can be operated from either a 110 to 125 AC/DC source, or from battery power. A Zenith No. Z-985 dry "A/B" battery pack along with two flashlight "A" batteries were required to operate the set in the absence of ac power.
Information source: The Zenith Trans-Oceanic, The Royalty of Radios - by John H. Bryant AIA, and Harold N. Cones, Ph.D.
Day One
Well I decided the other day it was time to get out the Zenith 7G605 Trans-Oceanic and see if it could be restored in time for the contest at the VRPS convention in October. We are having a category this year just for tube-type T/O's. It's going to take a lot of work to get this little set in good cosmetic and working condition. The cabinet is in fair shape, the genuine simulated alligator covering is pretty faded on top, some minor gouges on the sides, the escutcheons and the Waverod antenna need to be re-plated. I removed the chassis and it is in good shape with no rust, just dirty.
I notice there is a sheet of asbestos under the chassis which needs to be taken care of so there is no chance of asbestos dust floating around. Several coats of lacquer spray were used to seal it and then a piece of cardboard was cut the same size and glued over the asbestos. Another couple coats of lacquer was sprayed on just to make sure it was properly sealed.
The Chassis
Underneath the chassis is pretty clean. All the original Zenith capacitors are there and I don't see any evidence of anyone being here before. Some of the rubber covered wiring is very brittle and is obviously going to have to be replaced.
After a few checks with the ohm meter on the B+ line for any shorts and finding none, I decided I would risk bringing it up slowly on the variac. After the 35Z6 warmed up I got a nice loud hummmmmmmmmm indicating defective filter capacitors. A quick check with the frequency counter confirmed that the 1LE3 oscillator was working, at least on the broadcast band and two of the short wave bands so it can't be too bad off. I decided not to go any further until the I had replaced the filters.
The filter capacitors are mounted on top of the chassis in two metal cans. After removing the cans and with a little heat applied, the old capacitors pulled right out. Cloth covered wire leads were soldered to the new electrolytics and these were installed in the cans and held in place with hot glue. A piece of business card was cut to go inside the can opening with a hole in the center for the leads to come out, and the cans were then sealed with more hot glue.
After installing the new filter capacitors, the set was brought back up on the variac and the B+ checked OK. I set the selector switch to the AM band and a station down in New Orleans came in nice and clear.... not bad! Only there is still some hum which only appears when a station is tuned in. It sounds like modulation hum and I suspect it could be the bypass capacitor from B- to chassis ground. I unsoldered one end of the capacitor and tacked a new one in place and the hum is reduced some but still quite noticeable.
Another problem, now the set is doing funny things, static, cutting out. I discovered it happens when I move the tone switch escutcheon . The switches are connected via a cable bundle of seven wires, four of which are in a shielded jacket. The old rubber insulation on the wires is very brittle and is falling off and the wires are shorting out. It is so bad that the only thing to do is replace all the wires with some cloth covered wiring. It is going to be quite a chore and it is getting late and I'm tired so save that for tomorrow.
Day Two
Well lets see, there is just no easy way to do this. The wiring for the tone switches is traced against the schematic just to be sure I know where everything goes. Now to start removing the old wires. Because of the old insulation coming off I can't remove wires one at a time from the shielded jacket and shove a new one through so I have to remove all the old wires together. The shield is unsoldered from the chassis, then the wires are unsoldered from the switches and underneath the chassis and removed. New wires are installed, the shield is re-soldered to the chassis, and the bundle is relaced using waxed lacing cord. Except for the wire being cloth covered instead of rubber, the new cable bundle looks like the original.
Power is applied again and no more cutting out. The IF transformers are peaked by ear and plenty of stations are received on the BC band. The next step is to hook up the signal generator and check each SW band. Each band shows good signs of life. I next decided to check the voltage at the start of the filament string and it is setting at 9.2 volts which is just about right. At this point the set looks to be operational on all bands but I will wait until I have replaced all of the paper capacitors before proceeding with the final alignment.
Day Three
The tuning capacitor is pretty dirty and the rubber grommets that it mounts on are hard and coming apart, so it is decide to remove it and give it a cleaning and replace the grommets. I place the capacitor in a solution of half and half water and Naval Jelly and let it soak while I work on replacing the paper capacitors.
As I want keep the chassis as original as possible, this means replacing the insides of the Zenith caps with new mylars. There are 18 caps and some are really buried under wiring so this is going to take some time. Each capacitor is removed, the paper tube is heated and the old capacitor pushed out. A new mylar tubular is placed inside the tube, a piece of business card is cut just to fit in each end with a hole for the wire lead. Each end is then filled with hot glue.
After getting the capacitors replaced the tuning capacitor is taken out of the solution and rinsed off with water, using a tooth brush to clean off any residue, then blown dry with compressed air, being careful of the mica insulation under the trimmers, and set in the sun to dry.
While the tuning capacitor is drying I decide to hit the band switch assembly with some cleaner and give each push button a good workout to clean the contacts. All the coils on the band switch tower look to be in good shape.
After drying, the tuning capacitor bearings are oiled and it is then reinstalled with new rubber grommets. A final careful check is made of the chassis for anything that might have been missed.
Day Four
The chassis powers up OK, B+ voltage is good, and it is receiving stations, however the modulation hum is still present. I swapped out the 1LA6 converter and that solves the hum problem. The IF transformers were next aligned to 455 kc and then an alignment was done on all the bands. The set now receives as good as new, and after doing some polishing up, I pronounce the chassis restored.
The Cabinet
I next turn my attention to the cabinet. There are some places where the cabinet has been gouged and pieces of the simulated alligator covering is missing. The edges around the gouged areas are trimmed and squared up using an X-acto knife. Next pieces of the covering where it wraps around on the inside of the cabinet were cut to patch the missing spots. Because the size of the alligator scales vary, it was impossible to obtain an exact match, but the patched areas are small and hardly noticeable.
The nickel plating on the latches and hinges is completely gone, and the plating on the esctucheons is badly worn, so some re-plating is in order. The esctucheons, Waverod antenna, and handle brackets were taken to a plating shop, but since the hinges and latches are held with brads I decided that it would be to difficult to remove them so they are left in place. The leather handle is missing so a new reproduction handle is ordered from Antique Electronics Supply.
Day Five - Two And A Half Weeks Later
Finally got the escutcheons, handle brackets and antenna back from the plating shop after two and a half weeks. The plating came out really nice and was worth the wait. I painted the raised lettering on the escutcheons with black paint using a small artist's brush.
The hinges and latches were re-plated in place using a paste type plating solution that you brush on using a 3-6 volts DC voltage source. The steel parts were first plated with copper, then nickel.
GoJo hand cleaner and pumice was used to clean the cabinet coverning. The top of the case was really grimy but the cleaner did a good job of removing the dirt. Next, all traces of cleaner was removed with a damp rag and black shoe dye was applied to the entire surface. This covered small abrasions where the covering had worn through to the fabric underneath, making them practically invisible. I wiped off excess dye with a shop towel to kept the alligator pattern from turning too dark. A good polishing with neutral shoe polish made the "genuine simulated alligator"look really nice.
Day Six
After re-assembly, the Clipper looks pretty darn good I think. It operates on all bands, pulling in lots of stations with either the Waverod or Wavemagnet antennas on short-wave, just like it did in 1942. A reproduction owner's manual from the Radio Professors topped off the restoration. I would hope that Commander McDonald would approve, knowing that the little Clipper is tuning the airwaves once again.
Just finished in time too, as the VRPS convention is this week-end.
Check out Ted Peterson's excellent site on Zenith TransOceanics.
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