Restoration Idea 11
Electronic Restoration of an RCA 128 Radio with a Unique Family History
I received an email from Stephanie Sakioka in June 2014. She read the July 2013 article in the Orange County Register about my interest in saving old technology (mainly radios). She wanted to know if I was willing to restore an RCA 128 radio made during the depression era. I told her I had to give it some thought (I rarely do restorations from other parties). After reseraching this model I decided to accept the challenge but warned her that I don't repair radios (just to make them work) and that I do restoration (make sure they won't fail the next week) which can be expensive.
When I finally saw the radio and met with her, I explained the types of restoration, standard versus complete. A standard restoration is to keep the appearance of the visible electronics but with new components installed where they won't be seen. In contrast, a complete restoration involves both visible and not visible electronics looking original.
I asked why she wanted the complete restoration. What she told me was fascinating. Her husband's uncle (who is Japanese) purchased the radio new in 1933. In 1938 the FBI confiscated the radio, removed the shortwave (international band) electronics and returned the radio to him. The radio can only receive American stations. During that time Japan was already at war with China (3 years before US involvement). Naturally the US State Department was concerned about Japanese in the US. The FBI did a complete job in making sure that the radio inoperative for shortwave. For that reason alone it is a radio worth keeping.
1. Here are some photos of what the radio looked like before I started restoring. The photos show the cabinet (not part of restoration), the visible electronics and the underside electronice that are not visible. For a complete electronic restoration the original part shapes will remain. Any new parts will be hidden from view to the casual observer. By inspecting the electronics, I can tell that this radio had power supply repairs sometime between late 1950 to early 1960. Hopefully I will be able to remove these repairs and restore the look of the 1930s.
2. This is a rather complex layout. Although there is a lot of area under the metal chassis, many of the parts are tucked under other components making it challenging to get access to. In addition, the servicing documents were rather misleading and poorly described making replacement of parts challenging. Often I had to look over the circuit diagram or schematic and make a educated guess or go "over kill" regarding safe operating levels for parts selection.
3. The first phase of restoration starts at the visible electronics. These are the tubes, coils, connecting wires and power supply capacitors. The chassis was cleaned up and any rust removed and the surface protected. The tubes checked and bad ones identified and replaced. Wires were inspected and replaced if the insulation has been damaged or deteriorated. The big challenge is restoring the power supply capacitors discussed below.
a. The original was removed and carefully cut open with a hacksaw and vice. The cut areas are filed carefully so when I glued the pieces back it will be a good fit. Next the capacitor body was heated with a heat gun which allows the inside material be removed.
a. The original was removed and carefully cut open with a hacksaw and vice. The cut areas are filed carefully so when I glued the pieces back it will be a good fit. Next the capacitor body was heated with a heat gun which allows the inside material be removed.
b. The label if available was restored. Usually the labels start crumbling when any pressure is applied so a protective backing needs to be applied on the back by carefully gluing it on, then cutting around the label. Finally the label is reattached as shown.
c. New capacitors are installed into empty original containers and mounted back on the chassis. The tops are not glued back at this time, just in case I may need to remove the new parts.
4. Second Phase and Most Time Required- restoring the underside of chassis (non visible). The wires are inspected and I determine whether they need to be replaced or left alone. The problem is that the cotton covered wire is very difficult to replace because it is no longer used. Reproductions can be purchased but at very high prices. Luckily the wires look good and only very short pieces may need to be replaced so I can use newer better quality wire that won't be too noticeable.
5. Replace one by one all the paper capacitors and relabel them. In the early 1930's paper capacitors (invented by Robert C. Sprague) were metal foil wrapped between two insulating material (called the dielectric). This roll was inserted into a wax coated paper tube and the ends sealed with tar. Over time the tar would crack an allow moisture into the roll usually causing a short circuit (a common problem with early radios).
a. Restoring is slightly diiferent to the capacitors in item 3. to 4. above. The part is carefully removed from its location (important to ID where the part was connected)
5. Replace one by one all the paper capacitors and relabel them. In the early 1930's paper capacitors (invented by Robert C. Sprague) were metal foil wrapped between two insulating material (called the dielectric). This roll was inserted into a wax coated paper tube and the ends sealed with tar. Over time the tar would crack an allow moisture into the roll usually causing a short circuit (a common problem with early radios).
a. Restoring is slightly diiferent to the capacitors in item 3. to 4. above. The part is carefully removed from its location (important to ID where the part was connected)
b. Look at the left photo, at the center object for reference.
h. BELOW Examples of restored paper capacitors and short sections of modern wire added where necessary. 14 paper capacitors were restored. This was far more difficult than I thought because of the layout of the wiring and position. Many of the parts were placed on preassembled subassemblies as one can see in the above photographs. Easy when you start from scratch but a "pain in the neck" when you repair or restore.
With a heat gun, heat both ends to soften the tar (smells terrible so work in a ventallated area or wear appropriate respirator and wear protective eyeware and gloves). Carefully pull out original capacitor roll.
c. Clean outer surface of container and make sure inside has clearance to install new part.
d. Connect necessary leads to mount to new capacitor and insert into original tube.e. Install and solder leads of modified capacitor into original location.f. Plug sides of capacitor tube. I like to use cotton balls or paper towels so I can make repairs if for some reason the part fails. Purist like to seal the ends with epoxy or wax to make it look more authentic.g. Paste new label on capacitor if the original is missing or illegible.
6. Check all resistors to see if they were in tolerance to stated values. Early resistors were cylindrical pieces of carbon trimmed to a certain size to get the desired value. Wire leads were wrapped around the carbon for connections, then sealed and marked with a set of colors to indicate value. Resistors are used to provide a resistance to electricity because the electronics don't that much voltage or current in specific areas.
b. If out of tolerance, I have two choices. (1) If above the value add a modern resistor in parallel to original to get close enough, by soldering the new one under the original. Since modern parts are considerably smaller I can easily hide them. (2) If the value is under I can either remove the old one and replace it with a modern one OR add a new one in series to the old one by disconnecting one end of the old one and putting a new one in between the original connection and the cutoff resistor lead. The second situation is a rare one and this did not happen in this restoration.
8. Make electronic adjustments to coils and capacitors for optimum performance per servicing instructions. Proper test support equipment is highly recommended when doing this.
9. Top of chassis completed and bench tested. Notice the openings on the right side. The FBI removed all the shortwave electronics so the radio only receive US broadcasts.
10. Radio is bench tested before reassembly. Found that the ON-OFF switch was deffective and had to be completely replaced. Luckily I was able to drop by a local electronics store (FORD Electronics in Buena Park) that still had vintage parts available. Also the bulb covers had deteriorated and I had to find a translucent film and paint to simulate the original. Had to go down to a Hobby Lobby Store in Huntington Beach that had the closest thing I needed.
11. Glue to tops back onto the chassis mounted power supply capacitors. Use a clear epoxy. I could have painted the epoxy to hide the saw cut but if the capacitor needed to be repaired one can now find where to remove the cap to insert a new one.
12. Inside the cabinet showing the completly restored chassis. Noticed that I did not polish the chassis. Mrs. Sakioka wanted the original labels and writings on the chassis left intact.
13. Everything now works, Reassemble the radio and I gave the cabinet a steel wool and bees wax rubbing.
a. If the part is in tolerance (usually +/- 20% in that era) I left them alone. Five resistors were found to be out of tolerance. In the right photo the brightly colored parts are resistors.
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