Here are pictures of my Panasonic Model R-140 Six Transistor AM Radio. The top picture was taken before I started the restoration process and the bottom picture was taken after the restoration of this vintage transistor radio was complete. This blog is dedicated to the restoration of this beautiful depiction of cutting edge technology from the 1960s.
I acquired this radio from a local yard sale. It was covered in years of dust and white paint flecks and was subjugated to the dollar "bargain" bin as the battery tray was missing and you could hear loose parts bounce around inside the enclosure when you picked it up. Still, I saw that this R-140 had great potential.
As mentioned, the battery tray that held the four AA batteries that powered this radio was missing. The only thing left were two wires dangling in the rear battery tray compartment, see below:
The Ferrite core of the internal loop antenna had somehow snapped in two, possibly from the G force of a significant fall. This is the loose part heard inside the radio's case, see below:
The speaker grill, Panasonic logo, and dial indicator, had all once been emblazoned with silver paint. The paint accents had worn away due to years of wear and tear, see below:
In addition, there was paint flecks and smears on the fine leather case (see below). This radio was probably used as a "work radio" toward the end of its life to provide entertainment while doing chores like painting the house.
As with any radio restoration project, the first step is to disassemble the radio to ascertain damage and determine the steps required in the restoration process. The first step in the disassembly process of this radio was to remove is the tuning knob. It has one ornamental philips screw, circled in red, in the center that holds it to a variable air capacitor. The tuning knob pulls straight off once the screw is removed. See below:
Below is a picture of the front panel with the tuning knob removed. You can see the variable air capacitor shaft inside the radio.
Open the back cover of the radio and remove the internal cover that separates the battery tray from the electronics. Three screws, circled in red, hold the printed circuit board in place. See below:
You can pivot the printed circuit board exposing the speaker once the three mounting screws have been removed, see below:
Time to do some initial testing on this radio, I used my trusty bench power supply and some alligator clips to provide the required 6 Volts to the wires that used to connect to the battery holder. The only issue was determining polarity. In this case it was fairly easy as the battery holder wires were red and blue in color. The red being the positive connection and the blue being the negative. Success! You could immediately hear atmospheric noise coming from the speaker once the volume control was rotated to the "On" position. I could hear several AM radio stations with a few twists of the tuning capacitor's shaft. It looks like this radio will not require much in the way of electronic repair.
One thing I noticed was the volume control was a little "staticky" when changing volume levels. First, I had to remove the small bolt that holds the volume knob in place. See area circled in red below:
Spaying contact cleaner on where the wiper arm of the volume potentiometer contacts the carbon resistive element cleared it right up. I sprayed a little contact cleaner where the wiper arm meets the carbon resistive element then twisted the wiper back and forth through it's complete motion working the contact cleaner in.
Disassembly Part Two
I decided to completely liberate the printed circuit board from the cabinet to make detailing of the case exterior easier. I started by desoldering the speaker wires, circled in red below, that connect to the external earphone jack and internal speaker.
The black wire, circled below, must also be desoldered as well. It is the negative lead to external power supply jack.
Finally the external antenna wire, circled below, must be desoldered.
I soldered the wires of a small 8 Ohm speaker I had lying around to the proper points on the printed circuit board to aid in further testing. Otherwise, I would need to use alligator clips to connect the speaker in the case to proper points on the printed circuit board when testing.
Electrolytic Capacitor Replacement
As mentioned, the electronics of this vintage Panasonic R-140 AM Radio are functional. I can pickup multiple AM radio stations. As a preventative measure, I replaced all electrolytic capacitors in this radio. As electrolytic capacitors age, their electrolyte dries up causing their electrical capacity to drop and leakage current to increase. It is definitely a good idea to replace electrolytic capacitors that are over 50 years old!
Electrolytic capacitors are relatively cheap these days. $3 worth of replacement electrolytic capacitors will ensure this radio will continue function for many more years.
Electrolytic capacitors should be replaced with one of the same or slightly greater capacitance and working voltage rating. For example, in most cases, it is perfectly acceptable to replace a vintage 3uF 12Volt electrolytic capacitor with a new 3.3uF 50Volt one. You will find non-standard electrolytic capacitors values in electronic equipment that were built before the electronic industry instituted standardized values.
I replaced a total of five electrolytic capacitors on the radio's printed circuit board. The ones replaced are circled in red in the picture below:
I recommend picking replacement electrolytic capacitors that have the same size and color as the original. In this case, I compromised as I just had electrolytic capacitors of the same size but not color. The top electrolytic capacitor is the original and the bottom is its replacement.
Ferrite Core Repair
As mentioned, the Ferrite core inside the loop antenna broke into two pieces. One piece was jiggling around loosely inside the case of the radio.
I used Krazy glue to adhere the Ferrite core pieces back together.
Gluing the two pieces of Ferrite core should not affect the magnetic properties of the Ferrite Core. The "Core" is just made up of iron oxide suspended in a ceramic compound.
I could not tell the difference in this radio's performance between when only half the Ferrite core was in place versus the fully repaired Ferrite Core. The R-140 Radio is a great performer in either case.
Radio Case Detailing
Windex and an old toothbrush worked great for cleaning the speaker grill area and textured front panel of this radio.
The front panel is now ready for paint prep and masking.
I wanted to repaint the speaker grill silver like it was when the radio was new. I started by masking off the area that I didn't want painted silver. I used Frog Tape cut in thin ribbons using an X-Acto knife to mask the grill area. Larger Frog Tape pieces were used to mask off the area under the tuning dial. See picture below:
Finally, the masking job was complete. I extended the Frog Tape over the sides of the panel so as to prevent overspray from getting on the leather case. See below:
I sprayed Dupli-Color Silver Wheel Rim paint on the exposed grill section. I had this spray paint lying around to touch up a scuff on the rim on my Buick when I "curbed" it last year.
The Dupli-Color Silver Rim Paint really makes this radio's speaker grill stand out! See below:
Not done painting yet, I still needed to paint the border around the front panel and the dial indicator pointer. I first had to mask off the painted areas with Frog Tape.
Now to spray these exposed areas with Dupli-Color Silver Rim Paint.
I sprayed Dupli-Color Silver Rim Paint into the lid of the can then applied it to the Panasonic lettering with a fine paint brush.
Below is a picture of the finished product. The paint job far exceeded my expectations and really brings life back into this vintage radio.
Automotive Silver Rim Paint on Amazon!
Automotive Silver Rim Paint works great for touching up painted or pitted chrome parts on vintage radios.
I tried different cleaners and solvents to remove the paint flecks on the leather parts of the case. In the end I decided to leave it be as the cleaners and solvents were leaching the brown dye from the leather.
I used a liberal coating of Meguiar's Leather Cleaner and Conditioner to bring back the luster of the leather parts of the radio's case. You will find I use many automotive cleaning and waxing products during my radio restoration projects as I have them on hand for detailing my cars.
Meguiar's PLASTX Plastic Cleaner and Polish really brought the luster back to the dial tuning and volume control knobs.
Plastic Restoration Products on Amazon!
These products are intended for automotive use but also work great on the plastics used in vintage transistor radios.
Battery Holder Replacement
I found the perfect battery holder replacement on Amazon! The R-140 radio requires a battery holder that can contain four AA batteries. The four batteries must be two inline on both sides, so that it will fit in the slim battery compartment at the bottom of the radio's case. The leads of the battery holder I purchased were long enough so that it allowed me to wire it directly into the printed circuit board. This made the repair look very professional as I did not have to splice into the wiring of the original battery holder. Unfortunately, I forgot to take a picture of the battery holder install before final assembly.
Follow sections "Disassembly Part 2" then "Disassembly", both in reverse order, to reassemble the R-140 radio. Here is a picture of the inside of the case when the assembly process was completed.
Below is a picture when the internal cover is in place. The internal cover separates the electronics from the battery holder.
The front panel of the R-140 radio with tuning knob installed.
Here is a picture of the back panel of the R-140 radio, it flips up to expose the battery holder. The back panel is held close by two snaps.
Below is a video of the newly restored Panasonic R-140 AM Radio in Action!
Who Writes This Blog?
John is an IT professional from Cleveland, OH who enjoys amateur radio, ham radio, metal detecting,
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