Here is a before and after picture of my vintage Sears Silvertone Model 8020 radio. I think you'll agree that the makeover was a complete success!
About my Sears Silvertone 8020 Radio
I paid $5 at a garage sale for this vintage Sears Silvertone Model 8020 AM/FM Tube Radio. I don't think any other "garage sale enthusiast" wanted to touch it because:
1. There was physical damage to the volume control shaft and the volume control knob was missing. Most collectors know how hard it is to find matching knobs.
2. The cord was cut off so there was no way to test it.
3. It had some sort of brown syrupy substance on it that dried rock hard. I assume this substance to be dried varnish or wood stain.
4. The radio case is very unattractive. It first appeared to be just a painted metal case but after further investigation if turned out to be painted Bakelite.
I have a feeling that at one time this radio graced a table in the living room but toward the end of its life it was disposed to "garage duty" where things like paint, varnish, and other home repair substances were splattered on it. Finally, it failed to play music anymore and was placed in a dark corner of a garage or attic for many years. Then it made it to a garage sale as the owner was doing a thorough cleaning before "downsizing" for life in a condo community.
"Old Time Radios! Restoration and Repair" book on Amazon
I consult this book often during radio restoration. I grew up in the transistor and rectifier era and this book taught me a lot about vacuum tube and selium rectifier technology.
Step 1 Remove Chassis from Cabinet
Remove the four screws that hold the back panel in place. The locations of these screws are circled in the picture below. My Silvertone 8020 only had one screw in place. You must pull the back panel straight back about an inch as there is an Interlock that disconnects the AC power cord from the chassis. You can now lay the back panel down and disconnect the antenna wiring.
You need to remove four antenna wires, circled in red, that connect the chassis to the back panel. The two twin-lead wires connect to the terminals for an external FM antenna. The remaining black and green wire connect to the internal AM antenna which is glued to the inside of the back panel.
The Volume, Tone, AM/FM Mode, and Tuning knob must be removed. They just pull off. My Silvertone 8020 is missing the Volume control knob and shaft.
Four bolts hold the chassis to the base of the cabinet. Once removed, the entire chassis will slide out of the back of the cabinet. Only two bolts held the chassis of my Silvertone 8020 in place.
Here is the picture of the chassis, free and clear of the cabinet.
Step 2 Chassis Cleaning and Lubrication
I use compressed air to remove any loose dirt, then Windex moistened paper towels to remove any remaining dirt and grime from the top of the chassis. Windex moistened Q-Tips work great for getting into hard to reach areas. I only clean the tops of the vacuum tubes as I don't want to remove the markings from the sides of them.
I use Labelle 107 oil to lubricate all of the pulleys for the tuning dial indicator. This oil is safe for plastics. I have this oil on hand for my model train hobby.
I also use Labelle 107 oil to lubricate the shafts of the vintage potentiometers and AM/FM mode switch.
I use Labelle 106 Grease to lubricate the ratchet gear of the AM/FM mode switch. Contact cleaner is used on all contacts located on the two wafer switches circled below. I spray the contact cleaner on the switch contacts then rotate the AM/FM mode switch back and forth several times then repeat.
Labelle lubricants on Amazon
I use Labelle oil and grease for my radio restoration projects. I already have these products around as I am also a model railroad enthusiast. These products will not harm plastic.
Step 3 Test Vacuum Tubes
Unlike semiconductor transistors that have a near infinite lifespan, vacuum tubes age and become less efficient. In addition, their filaments burn out rendering them inoperable. It is always a good idea to test all vacuum tubes in a radio you are servicing before doing any more troubleshooting. In the case of my Silvertone 8020 radio, the 50LG6GT Audio Amplifier tube and 6C4 FM RF Amplifier tube tested marginal on my Eico Model 635 Vacuum Tube Tester. I chose to replace them.
In addition, make sure that that the right tube is in the right socket. This will save you troubleshooting time in later. A 12BE6 and 12BA6 vacuum tubes were in the wrong sockets in my radio.
Step 4 Volume Control Replacement
As you can see in the picture below, the shaft of the Volume control potentiometer has been completely snapped off.
The first thing that needed to be done is to make a note of the wire connections to the Volume control potentiometer. You will need to connect the wires to the same terminals on the replacement. I then unsoldered the wires, removed the nut that holds the Volume control potentiometer in place. Finally, I removed the broken potentiometer from the chassis.
By measuring the resistance across the end terminals of the original Volume control potentiometer, I had determined that the replacement needed to be of the 1 MOhm Audio Taper type.
I just happened to have the right replacement potentiometer in my parts drawer, the only problem is that the replacement had an integrated on/off switch.
The on/off switch component of the replacement potentiometer is contained in the black plastic piece at the rear. It can be easily removed by drilling out the rivets that hold it in place.
Here is a picture of the on/off switch component, circled in red, removed from the replacement Volume control potentiometer.
I had to remove the metal shield from the back of the replacement Volume control potentiometer in order to remove the remnants of the rivets. The metal shield is just held in place by four metal tabs that can easily be bent for removal and installation.
The shaft of the replacement Volume control potentiometer is longer than the original one. I made this observation by comparing it to the shaft length of the tone control. I used a Dremel, with cutoff wheel attachment, to render it the proper length.
In addition, the shaft of the original Volume control potentiometer had a flat spot on one side to key the knob to the proper position on the shaft. I once again turned to the Tone control potentiometer in order to determine the proper position of the flat spot. I then used my bench grinder to grind a flat spot onto the shaft.
Here is a picture of the replacement Volume control potentiometer bolted to the chassis with the leads soldered in place. I temporarily installed the Tone control knob to check for knob fitment.
Step 5 Electrolytic Capacitor Replacement
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 60 year old electrolytic capacitors like the ones in the Silvertone 8020!
Step 5a - Restoring the Multi-Section Capacitor
Multi-section capacitors, which were aluminum cans containing several discrete capacitors all connected to a common ground, were popular in the 1950s. There were used mostly in the power supply sections of vintage electronic devices. You can purchase replacement multi-section capacitors but they are expensive. I typically rebuild them by replacing their guts with inexpensive discrete capacitors of the same or slightly greater capacitance and working voltage. The multi-section capacitor in the Silvertone 8020 is circled in the picture.
The multi-section capacitor in the Silvertone 8020 contains the following discrete capacitors:
Capacitor A 40uF @ 150Volts
Capacitor B 80uF @ 150Volts
Capacitor C 40uF @ 150Volts
Capacitor D 20uF @ 25 Volts
The components connected to it's base terminals, circled below, must be desoldered before removing it from the chassis.
Here is a picture of the multi-section capacitor removed from the chassis. The center insulated terminals connect to the positive connections of the contained electrolytic capacitors while the terminals towards the edge connect all internal electrolytic capacitors to a common ground.
I use wire cutters to cut the crimped bottom of the multi-section capacitor. Then I use needle nose pliers to pull the crimped sections away from the base. This allows me to pull the guts of the multi-section capacitor out of the metal can.
The anatomy of a multi-section capacitor. All four internal capacitors are rolled up into one assembly.
I was able to wire all four replacement electrolyte capacitors to the base of the multi-section capacitor. The aluminum can, when glued in place, will conceal the replacement capacitors.
Pictured below is the refurbished multi-section capacitor installed back into the chassis. You will never know it was refurbished once the aluminum cover is installed!
I use a Dremel with cutoff tool to remove the area from the base of the multi-section capacitor's aluminum can that I bent with needle-nose pliers. Hot glue holds the aluminum cover in place over the multi-section capacitor's base.
Step 6 Replacing Individual Electrolytic Capacitors
I also replaced an 8uF 50Volt Electrolytic Capacitor, circled below.
It was replaced with a modern 10uF 50Volt Electrolytic Capacitor, the package of the new capacitor is much smaller.
Step 7 Replacing Molded Paper Capacitors
Molded paper capacitors, like the one circled below, become very unreliable with age and should be replaced with one of similar capacitance and equal or above voltage rating. Molded paper capacitors are not polarized although they may have a black band on one side indicating which lead is connected to the outside foil. I replace molded paper capacitors with new Polypropylene type.
Circled below are all of the molded paper capacitors that needed replacement.
I replaced molded paper capacitors with new Polypropylene ones. Polypropylene capacitors are inexpensive and exceed the specifications of the original molded paper capacitors in every aspect. Circled below are the replacement Polypropylene capacitors soldered in place.
Step 8 Inductor Rebuild
During my initial testing of the chassis, a test lead accidentally shorted to ground one of the Inductors on the incoming power connection. This burned an open in the copper windings.
I decided that I could rebuild the Inductor. I counted the windings on the existing "good" Inductor and determined the wire gauge of the windings by comparing a piece of the burned out winding to the enameled copper wire I have in stock. I removed the original burned windings from the core of the Inductor then used denatured alcohol to remove any burn residue.
I then carefully wound new enameled wire on the Inductor core the same number of turns as the on the existing "good" Inductor. Hot glue temporary held the windings in place.
I used Cyanoacrylate based Loctite Super Glue to fastened the windings permanently in place to the Inductor core. I removed the Hot Glue once the Super Glue was dry.
Next I use an X-Acto knife to scrape the enameled coating off the ends of the windings then soldered the wires to the Inductor's two terminals. The Inductor rebuild is now complete.
The last step is to solder the rebuilt Inductor back into the chassis. I also replaced the charred 120pF capacitor next to it.
Step 9 Wire Replacement
The insulation on one wire became brittle and fell off exposing the conductor.
I replaced it with the green wire seen below.
Step 10 Chassis Testing
I created a temporary connection to the AC line using a polarized cord. I connected the cord to the chassis so that it would be near ground potential and not "Hot". The Silvertone 8020 is of a transformerless design and you have to be extremely careful when working around the exposed chassis as it could pose an electrical shock hazard.
I did not have to perform much troubleshooting on my Silverstone 8020. I could immediately hear an AM Radio station upon power up and with an external antenna connected to the AM antenna lead. Circled below is the lead I connected the external antenna to for AM Radio reception.
I was not so fortunate in FM mode and could only pickup one faint station with a good external antenna connected to the FM antenna lead. Circled below is the lead I connected the external antenna for FM Radio reception.
I later determined that a 12BA6 Tube in the FM 2nd IF Amp stage developed an issue since first being tested. My tube tester's "Short-Grid Leakage" light glowed immediately when I attempted to test it. Back to my vacuum tube collection to find a suitable replacement!
Step 11 Back Panel Repair
For some reason, the AC power cord was hacked off on my Silvertone 8020. Circled below is where the AC power cord connects to the back panel.
The back panel incorporates an Interlock which disconnects the AC power line from the chassis when it is removed. In order to replace the AC power cord, you must drill out the four rivets that hold the Interlock and the two rivets that hold the AC power cord strain relief in place. Circled below are the locations of the rivets.
I picked up a polarized AC line cord from Amazon for under $5, it is intended as a replacement cord for a laptop.
I cut off the connector of the AC power cord that connected to the laptop's power supply then treaded the cord through the strain relief. I then striped the ends of the cord and soldered to the lugs inside the Interlock. The small blade of the AC power cord should connects to the smaller connector in the Interlock.
I then used 8-32 screws, star-washers, and nuts to secure the Interlock and the Strain Relief to the back panel again.
Pictured below is how the back panel looks after the Interlock and power cord strain relief were bolted back into place.
The last order of business was to replace the paper capacitor located on the Antenna Terminal Block.
I chose to replace the paper capacitor with a ceramic one of equal capacitance and a higher Voltage rating.
The final step was to test that the AC line cord was properly wired. If properly wired, there AC Voltage potential between the ground lead on an AC outlet and the metal chassis of the Silvertone 8020 should be less than one Volt.
Step 12 Detailing
I used Silver Enamel Modeler's Paint to paint the Dial Pointer. The original paint had chipped off years ago. I used a sheet of paper behind the Dial Pointer as a mask to prevent the paint from getting on the Dial Scale.
Meguiar's PlastX works great for removing scratches and oxidation from the clear plastic Dial Scale lens. On the left is the before picture, and to the right is how it looked after some vigorous PlastX polishing.
PlastX also works great for cleaning and polishing knobs. I use a toothbrush to clean the ridges on the sides of the knob.
Meguiar's PlastX on Amazon
Meguiar's PlastX works great for cleaning up vintage knobs or to remove the "yellowing" of clear plastic lenses used over the tuning indicator. I also use other Meguire's automotive detailing products to bring back the luster of old radio cabinets.
Once the knobs were cleaned, I carefully masked off everything on the knobs but the center areas.
I sprayed the centers with some silver paint I had in my arsenal.
I removed the masking tape once the silver paint on the knobs were dry. I then used Silver Enamel Modeler's Paint to paint the letters on the knob using a sharpened stick.
The metal speaker grill, and cardboard mask that sits behind the grill, were painted Matt Black.
Step 13 Cabinet Refinishing
The cabinet of my Silvertone 8020 is made of Bakelite painted a metallic green color. There was a lot of scratches of the paint exposing the Bakelite. I chose to repaint the cabinet.
I wet sanded the exterior of the cabinet using 600 Grit Sandpaper in order to get the primer coat to adhere better.
I masked off the openings in the cabinet and applied Prep-All degreaser to the exterior. A liberal coating of Filler Primer was applied to the cabinet's exterior.
After allowing the Filler Primer to dry for 24 hours, I thoroughly wet sanded the exterior with 600 Grit Sandpaper. I would sand the Filler Primer, then wipe down the exterior of the cabinet looking for imperfections. Then re-sand the areas with imperfections until the exterior of the cabinet was completely smooth to the touch and imperfection free.
Time for paint prep, I re-masked the cabinet openings then once again applied Prep-All degreaser to the exterior. The cabinet is now ready for a paint job!
I chose to paint the exterior of the cabinet a Rust-Oleum Silver Metallic color.
Rust-Oleum Silver Metallic spray paint on Amazon
Step 14 Final Assembly
I decided to install rubber feet, circled in the picture below, so as not to scuff the bottom of the cabinet.
The Dial Scale lens just clips in place.
The speaker grill is installed, then the cardboard mask. Five metal clips, circled in red, hold the whole assembly in place.
Now its time to check the exterior of the cabinet for fitment of the Dial Scale lens and speaker grill.
The next step is to slide the chassis into the cabinet from the back. Slide the chassis in as far as it will go forward. I also replaced the pilot lamp, circled below, during this step as the original had burned out. I used a 4-Watt 120 Volt bulb commonly used in night lights as the replacement.
The next step is to secure the chassis to the cabinet. This is done by turning the cabinet on its side and securing it with four 8-32 screws and flat washers. See areas circled in the below picture.
The next step is to connect the antenna wires from the chassis to the back panel. I had to add wire extensions to the FM antenna connections so they would reach the antenna terminals.
Finally, the back panel can be installed in the cabinet. Make sure the AC power cord Interlock connects properly to the two pins on the back of the chassis. I used four 8-32 screws and washers to hold the back panel to the cabinet. There locations are circled in the picture below.
Below is a picture of my Silvertone 8020 Radio after my complete makeover. Looks pretty good if I say so myself. The contrast between the silver cabinet and the matt black grill reminds be of the face of a Cylon from Battlestar Galactica 1978 Television Series! As you can see I still need to find a replacement volume knob.
Video of my newly restored Sears Silvertone 8020 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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