Make: Silvertone
Model: 3004
Year: 1956
Case: Plaskon (Not Bakelite or Catalin)
Tubes: 5 (also known as the "All American 5 tube radio" or "AA5")
Receiving Bands: AM (Broadcast) only.
While awaiting parts for the RCA my mother walked into the kitchen one morning carrying her Silvertone 3004 that her mother had bought brand new from Sears for her in 1956.
The poor thing had seen far, far better days. It was completely dead, filthy from where roaches had set up housekeeping in it, and after a quick inspection of the components had not one but two dead capacitors.
Visual Inspection
I began with a simple visual inspection of the radio making notes on what needed to be done. About the only thing not needing attention was the dial string.
The radio in it's entirety was filthy so a good cleaning was in order. The tensile leads from the component board to the speaker were literally corroded away into a green powder now laying on the bottom of the chassis.
The case had multiple cracks and was covered in years of dust compounded by minor clouding due to 50 years of being cleaned with furniture polish, but worst of all a 2 inch triangular piece of the plastic was missing entirely.
The masonite back had all but disintegrated and there were multiple tape marks on the case where attempts had been made to hold the back/antenna in place.
One internal capacitor had been replaced with a Sprague Atom (most likely serviced by my Uncle in the 1970's) that was too large to fit under the chassis, so it was mounted exteriorly thus pushing the masonite back even further out of it's proper place.
Troubleshooting
My first action was to download the schematic for this radio and check the various components. Since I had planned to completly recap the radio anyway I didn't pay too close attention to the capacitors and just gave them a cursory check with the VOM. I found two dead caps but all the resistors and tubes checked good, and there were no open or shorted coils.
Before Recapping
I listed all the parts I needed and dashed off a quick order to AES.
The Recap
Since this was a small radio the recap was finished quite quickly. I did, however, take great care to protect the "Couplet PC-150", an early attempt at an integrated circuit, from any heat or vibration. This was tricky in a couple of spots and made good use of the Archer Heat Sink.
After Recapping
Speaker Problems
Once the radio was in the pink it was time to tackle the speaker.
Bug eaten and as brittle as autumn leaves this was not going to be an easy task. In attempting to clean the corrosion away (so new tensile leads could be soldered on) the paper began to tear away from the frame, and all attempts to stop it simply made the situation even worse. The first tear was almost 1/4 way around the circumference of the cone. In trying to save the speaker I had hit the proverbial iceberg.
I found that I was about to be immersed (sink or swim) into the world of speaker reconing.
Since the coil and spider were unharmed, I simply flaked away the rest of the paper and ordered a new cone. In the meantime I used fingernail polish remover (acetone) and Q-Tips to gently dissolve away the tar-thick speaker glue from the coil leads and voice coil form.
Unfortunately, the only cones available to me (not being a professional speaker repair shop) were 4½ inches in diameter or 6½ inches in diameter. This was problematic as it was originally a 5 inch cone.
I ordered both the 4½ inch and the 6½ inch cones, thinking I could cut one down or hybridize the two. I found though that there was actually a smaller lip just inside the frame into which the 4½ inch speaker cone fit perfectly!
To mount the spider and coil to the new cone, I simply poked a couple of holes through the cone and, using tweezers, fed the leads through the cone. I had to do a very little and very precise bit of cutting on the cone to get the new cone to fit on the voice coil form, but this was minor. I then glued everything in place with plain old Elmers School Glue and let everything dry VERY THOROUGHLY!
After this it was just a matter of CAREFULLY soldering the new tensile leads to the coil leads.
Then aligning the coil to the magnet and gluing everything to the frame. A small weight held everything in place while the glue dried. Again, I just used Elmers School Glue.
Before soldering the tensile leads to the component board I wanted to be sure that everything was in working order, so I hooked my old MP3 player (seen in the bottom left of the above photo) to the tensile leads and sure enough, out blared Blue Oyster Cult.
A quick solder up and we're ready to switch on again, this time to a nice clean sound... well, almost. A bit of static in the volume knob indicated the need for a couple of squirts of DeOxit but once that was done, problem solved.
The Cabinet
On to that nasty cabinet.
Even though the Silvertone 3004 is made of Plaskon and not Bakelite or Catalin, Plaskon can still lose it's luster, and when cleaning with water you easily get a whiff of something that smells like petroleum.
I decided, since I didn't have the proper cleaning materials at the time, to clean most of the grime away with a very mild detergent and water. I opted for Ajax dishwashing liquid and while this did indeed do the trick of removing the grime, I also began removing COLOR from the top of the cabinet! Which leads me to my first warning of this entry.
A VERY LIGHT WASH EVEN WITH MILD SOAP IS INDICATED HERE!!!
ONLY USE WATER ON PLASKON IN CASES OF SEVERE GRIME!! (otherwise use Glayzit or Novus cleaners and polish)
To clean the louvers in front of the speakers, I simply wrapped the rag around a screwdriver
After giving it a good scrub down inside and out, I gave it a couple of coats of Glayzit, giving each coat a good rub in with a clean lint-free cloth.
Cracks, Chips and Chunks.
Finally it's time to deal with those pesky cracks and that missing chunk of plastic.
For this I chose a plastic repair kit called Plas-T-Pair from Radio Daze and, rather than having to paint it, I chose instead to add a bit of dry pigment to the mix.
I chose Gamblin's Burnt Umber from Blick Art Materials which matched SO perfectly that in normal lighting it's actually hard to see the repair.
Note: When this picture below was taken the plastic was still wet and thus slightly lighter in color than when dry. The flash of the camera also contributed to the lighter color. When dry, the color match was truly perfect.
Even though this topical approach worked fine, it would have worked even better if I had simply removed the chunk of plastic I was repairing (since it had already fallen out a couple of times) and applied the Plas-T-Pair along the edges of the break as one would apply glue. As I said, this really didn't matter except for cosmetic purposes as the Plas-T-Pair still made a beautiful permanent fix.
Re-fashioning the Masonite back
Last but not least we need to tackle that disintegrating masonite back and antenna.
When I ordered the dry pigments from Blick's , I also ordered a couple of sheets of Masonite to replace this back. I ordered a couple of sheets just in case I made a right dogs dinner out of the first one.
I began by removing the antenna from the old masonite back. This was simple as it was simply glued to the board and as the board was crumbling away anyway, the glue lifted cleanly off.
I then clamped the old back to the new masonite board and used it as a stencil to transfer the pattern to the new board.
A bit of drilling and a few strokes of a coping saw and the new back was complete.
A bit more Elmer's Glue and a touch of the soldering iron and everything was finally in place. I admit, the new back isn't nearly as nice as the original, but hey! it works!
UPDATE
Now that the radio is working again, we're back to the problem that landed it in the closet in the first place. My mother explained that the reason she put it up was because it would play for a while then start being plagued by terriable static and a garbled sound. She said she would just reach in the back and thump one of the "square tubes" and it would work again for a while, then start all over again.
You can hear the problem for yourself here (Radio3.wav) but be advised that this is a LARGE FILE (about 2.6 mb) so don't open it if you don't have a fast connection. The microphone is crappy so the audio is pretty low but I never touched the radio while this was recording.
It turns out that this is "Silver Mica Migration" or what some call "Silver Mica Disease" ha ha. Essentially the silver has creeped out of the silver mica capacitor in the IF coil transformer (the square metal cans) and is wreaking havoc on the radio.
This means I will have to open the IF cans and replace the capacitors (See how to do this here), or simply bypass the IF interstage coil altogether (See how to do this here). I'm going to try replacing the caps first and if all else fails, I'll just wire around the problem.
Stay tuned, it's not over yet.
UPDATE II
After ordering (and receiving) the Silver Mica capacitors to recap the IF cans I hit another problem. While carefully disassembling the IF coil, the lower slug literally fell apart and into my hand. I was careful not to touch the slugs or the hair thin wires as well as to protect it from any un-necessary vibration, but I guess the vibration of just handling it was enough to finish off the slug.
After relaing this incident on the message board, a friend mentioned he had one in his junk box and dropped it in the mail to me. The day was saved. Needless to say I was feeling lower than a welldigger's heel.
When the replacement coil arrived I was even MORE careful handling it but this one held together just fine. I desoldered the tiny hair-thin leads from the legs being careful not to get them mixed up and then unsnapped the capacitor base from the coil form.
I then drilled out the rivet in the center and removed the top plastic plate before removing the mica spacer. I then soldered the new silver mica capacitors in place and replaced the coil form as shown in the tutorial above, but when I attempted to replace the metal shielding "can", it wouldn't fit despite my best efforts.
As I sat staring at it, scratching my head a bit, the question arose in my mind "why am I simply parroting the tutorial? Who say's the capacitors have to go INSIDE the can? As long as they are across the coil?".
So I removed the capacitors, soldered the leads back onto the legs and reassembled the can.
After putting it, sans-capacitors, back on the chassis, I then soldered the two silver mica capacitor across the LEGS of the coil (which will make an easier repair if they ever have to be replaced again) , repeated the same for the other coil and plugged it back into the AC.
Viola! It now sings like a canary without the static crashing and garbled audio of the Silver Mica disease. :)
Fin.
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