Posts: 42
Threads: 7
Joined: Apr 2009
Interesting construction of the capacitor pack.
Tools: one vise clamped to a picnic table, pliers, a large screwdriver and a propane torch. Heat both sides until the packing melts, then grab the wires with the pliers and pull the packing out.
There are three paper capacitors (C64-C66) were held together side-by-side with a rubber band. Three resistors (R23, R24 and R26) lay across the capacitors. One is 0.1watt and two were 0.25 watt. The bundle was wrapped in thick paper, inserted in the rectangular cannister and filled with tar of unknown origin or toxicity.
I'll assemble the new capacitor and resistors in similar fashion but will omit the tar unless someone knows better. I'm not sure why the pack was filled with the tar unless excessive heat or fire was a concern. Rather than cobbling together a couple of half-watt resistors to make replacements, I've got some one-watt resistor with the exact ohms and I'll use those along with the yellow metalized polyester film capacitors. Cardboard from a cereal box or beverage pack should provide sufficient insulation.
The radio came with a book, RCA Receiving Tube Manual. Very helpful in identifying the pins that were not clear in the schematic. This part of the circuit is connected to the grid so voltage (watts) shouldn't be an issue. That's my look at it.
Posts: 42
Threads: 7
Joined: Apr 2009
The radio works wonderfully except for a noisy volume control. The one reference on radio servicing that I have says replace the pot. That may have been a good idea in 1940 but I've tried to find similar ones today and come up blank. Three tabs hold the housing on pot. I'll have to desolder a 33 pf capacitor to remove the cover. Bill Turner's Dial Cover provides a nice review but it's the only one I've found. Perhaps no others are needed. Funny thing is that I could just about throw a rock and hit his house from my back yard. Small world.
The volume control is not always noisy so I'm not sure if I should mess with it. Any suggestions would be welcome.
I spent several hours working cleaning and lubricating the coarse and fine tuning shafts and the band selector. The tuning shaft would have been a major project to remove so I opted to use a small amount of Liquid Wrench and a couple of drops of Marvel Mystery Oil to loosen the dried up lubricant in the shaft. Both turn freely and independently now. The band selector is almost a mechanical engineering marvel. The dial face on the radio is an inverted, U with short legs pointing down. The dial is a round disk with the five bands printed on it in a pinwheel pattern. The selector knob is a pivot point with two levers that's connected to the range selector switch shaft and a gear that turns and clicks the the dial in one of five positions. There are six points that must rotate freely for the selector to work. I had to remove the dial and polish the shaft and hole with 0000 steel wool before lubricating it with a very small dab of lithium-based grease and a drop of MM Oil. All rotation points were oiled and alignment was checked to minimize binding. It turns freely but requires a good grip on the knob to make the change.
The person that used the radio listened to a lot of shortwave. There's a spot on the long wave band of the dial that's faded. When the radio is set to listen to short wave, that spot is directly above a lamp.
Al long wire connected to the A1 terminal provides great reception.
Still bothers me that I couldn't read the schematic well. - simple things too like grid voltages need to be negative. I have a lot of facts that are isolated now. Perhaps they will come together in time. On the bright side, I was able to replace worn out wires and most of the capacitors and resistors without incident buy clipping or desoldering all of the components at a node and solder the new replacements in place before moving on. Only one silly mistake. The radio wasn't working after I reassembled it and installed the old tubes. All of the tube voltages were good and a little higher than spec. Thank you agina, Ron, for explaining that this is normal and OK. A 200 Hz signal on the audio grids showed that part of the circuit was working fine. After a day or two of looking at the wiring and documenting the voltages at the nodes I notice a desoldered lug with nothing attached. A loose end of a wire that's connect the the third IF coil was hiding under two wires against the chassis. When that wire is not connected you get nothing. Connect it and the radio works.
On to the cabinet now. I want to the ethanol to remove the old finish. This could take some time.
One thing I must comment on is the dial cover. It's plastic, not glass. Did RCA really spend all of the time an money to make such a fine radio and use a plastic dial cover that yellows and scratches over time?
Posts: 42
Threads: 7
Joined: Apr 2009
Removing the old checkered finish
I had to take the case outside due to the fumes and potential mess. I used an old bed pad over my picnic table to collect whatever runs off. Lots of ethanol, 00 steel wool and elbow grease. I had to use liquid stripper and a putty knife in the seam. Once it was dry, I wiped it down with 0000 steel wool. No sanding. No chance of taking off 70 years of patina. A quick once over with a rag damp with turpentine was the last step.
The finish.
After much thought I decided to use amber shellac and finishing wax. First, the weather outside was not suitable for spraying lacquer and there was no way I would do that in my basement. I don't like spraying outside anyway because I always get dust or grit somewhere. Shellac wipes on and has little if any fumes. Second, the radio was made with a shellac finish and it will end it's useful days with it. Third, French polishing gives a finish I do not believe can be duplicated by any other method and is relatively simple to repair. Forth, finishing wax can protect the shellac. The shellac protects the wood. The finish product is stunning.
The project turned out better than I could have imagined. The hard part now is finding a place to put it. My wife loves the Philco 40-201 in the dining room and there's no room in the living room. Look like the bedroom is the only place left. I will be a tight fit.
