The Capacitor Cover-Up: Restuffing Vintage Radio Cans with Modern Tech

Guess what I'm up to?

Fixing an old radio. Like, from the 50s: a Grundig ("Majestic USA") 8098 console radio with record player and reel-to-reel tape deck.

it's a beauty!

It belongs to a friend, who asked, "Do you repair old radios?" I asked for pictures, did a little research, and decided, "This sounds like an interesting project." The radio is now in my garage, disassembled, as I do a recap on it. Here's some background, and specifically the "can/dual-cap" bits (which the title of this post references). And a picture of the main chassis on my "work bench" (i.e., a folding table in my garage).

the patient on the bench :)

The "Hum" of Death

If you mess around with vintage electronics long enough—specifically tube radios from the 40s and 50s—you learn to fear "The Hum." You plug in a beautiful piece of history, wait for the tubes to warm up, and instead of clear audio, you get a loud, angry 60Hz buzz that sounds like a transformer having a panic attack.

The culprit? Almost always the electrolytic capacitors.

In these old sets, some of the filter capacitors live inside a shiny aluminum "can" mounted prominently on top of the chassis. It looks cool. It looks industrial. It also happens to be filled with 70-year-old dried-up borax paste and despair.

The rest of the caps? They are buried in a jumbled mess of wires, connectors, caps, resistors, and who knows what else underneath the main board. Pro Tip: Take pictures when you're working on these things. Lots of pictures. So you know what to reconnect where.

The Dilemma: Fix It or Fake It?

When these old cans fail, you have two choices:

1. The "Ugly" Fix: Clip the wires, leave the dead can disconnected on top (for looks), and solder tiny modern capacitors underneath the chassis. It works, but if you flip the radio over, it looks like a confused spider web of new components.
2. The "Purist" Fix: Buy a reproduction can capacitor (which costs about as much as the radio itself).
3. The "[LAPSE... brain dead]" Fix (or the "vintage-sort-of-look" fix): You cut the old can open, scoop out the toxic guts like a forbidden pumpkin, and hide brand new, tiny modern capacitors inside the old aluminum shell.

Naturally, I chose option 3. Because why make it easy when you can make it messy?

Anatomy of a "Stuffing"

The specific patient on my workbench today had a "dual-section" can. Back in the day, manufacturers would stuff two or three different capacitors into one cylinder to save space. Today, modern technology has shrunk components so much that the replacements are smaller than the tip of my pinky finger.

The goal? Fit the new tech into the old skin so that nobody—not even the radio—knows the difference.

Step 1: The Decapitation

First, you have to get the can off the chassis. This usually involves wrestling with twisted metal tabs that have been solidified in place by solder that was applied when Harry Truman was president.

Once it's off, the real fun begins. If I was good at this, I would have taken a pipe cutter (or a hacksaw, if you’re feeling aggressive) to the base of the aluminum can. You have to go slow. You want to cut the crimp just enough to separate the top from the base without mangling the aluminum.

My approach? Less care, twisting the base up with needle-nose pliers to be able to get the insides out. (This did make "reassembly" significantly more difficult, since the can was distorted a bit. We'll get to that later.)

Step 2: Excavating the Goo

This is the part nobody warns you about. Inside that can is a roll of foil and paper soaked in electrolyte. Sometimes it’s dry and crusty; sometimes it’s a tar-like substance that hates you personally. You have to drill, pull, and scrape until the can is hollow. My example was a messy, semi-hard goo. I eventually got it out.

Once out, clean out the can on the inside. WD40 can be a good choice, maybe finish with alcohol. And a lot of rubbing in a tiny little can. I used an old toothbrush.

Step 3: The "Ship in a Bottle" Wiring Job

Once the can is hollowed out and cleaned (and you’ve washed the forbidden chemicals off your hands), you’re left with an empty aluminum shell and a fiber base with the original mounting lugs.

Now comes the math. My original can was a "Dual 100uF at 450V." My replacements? Two tiny modern 100uF capacitors that look like Tic-Tacs compared to the original behemoth.

This is where it turns into a high-stakes game of "Operation."

1. Drill Baby Drill: You could drill tiny holes near the original terminals on the fiber base. Mine? No such luck - that fiber base was no longer present, just a ring. So, careful placement to avoid cross-connecting the positive leads, then some heat shrink around those positive leads to keep them isolated.
2. Thread the Needle: If you drilled tiny holes, feed the positive leads of the new capacitors through the base and solder them to the original positive lugs. My case: I just inserted the can into place and soldered the now-heat-shrink-covered positive leads to the appropriate locations (don't forget to take pictures BEFORE you take anything apart!).
3. Common Ground: In these old cans, the aluminum case itself is usually the negative connection. I twisted the negative leads of the new capacitors together and soldered them to the appropriate ground lug (you could also solder them to the metal ring on the base and from there to the dedicated ground location).

It looks ugly inside. A mess of wires and heat-shrink tubing floating in empty space. But that’s the beauty of it—once the lid goes back on, nobody sees the chaos. (Well, if you pull the chassis out you can look up inside the now-open can... but this isn't a "show" radio, it's just trying to get it working again). It’s like shoving all your dirty laundry under the bed before a date comes over.

Step 4: Hiding the Evidence

With the new capacitors tucked safely inside the shell, it was time to reattach the aluminum cylinder to the base.

If I'd used a pipe cutter, I'd have had a relatively clean seam. A little bit of J-B Weld (epoxy) on the lip and pressing the can back together would have been the finish. Some people use aluminum foil tape to cover the cut; others just mount it so the cut faces the back of the radio.

In my case, I used pliers to "reform" the circular end of the can. It left some ugly creases, unfortunately, but eventually I was able to get it "circular enough" with the can mounting lugs aligned with the board slots. Then I could bend those lugs to hold the can in place.

Once installed back on the chassis, it looked… 98% authentic. Unless you got out a magnifying glass, you’d swear it was the original part from 1952. Maybe.

Step 5: The "Smoke Test"

This is the moment every electronics hobbyist loves and dreads. And this is the part I haven't gotten to yet, as I'm still replacing other caps on the chassis main board. When I finish all those, I'll continue with this step.

I'll plug the radio into a "Dim Bulb Tester" (a safety device that prevents the radio from exploding if I messed up). I haven't made this "Dim Bulb Tester" yet... but according to Phil's old Radios, it's quick to build. I'll definitely be doing that before plugging this thing in.

Once that's done... here's the "prophetic ending" to my restoration:

I flipped the switch.
I watched the tubes start to glow orange.
I waited for the smell of burning ozone or the "POP" of a backwards capacitor.

Nothing.
Silence.

I turned up the volume knob. Instead of the angry "HUMMMMMMM" of death, I heard the gentle, white-noise hiss of static. I spun the dial, and suddenly, a preacher AM station faded in, crystal clear.

Hopefully it will all go as smoothly as that. Hopefully the recapping is all this bad boy needs, and THIS bad boy (me) soldered up everything correctly on the first go. We'll see, and I'll report back whether it was smooth sailing (or whether I was burning down the house).

Why Bother?

A sane person would have just bought the $40 reproduction can. A lazy person would have just soldered ugly yellow capacitors under the chassis.

But there is something deeply satisfying about "restuffing" these old cans. It keeps the aesthetic of the radio honest. It respects the original engineering while secretly updating the engine. It’s a stealth restomod.

Plus, I saved about $35, which is almost enough to buy another broken radio that I don’t need (although it might be fun, since when this one is done, I'll have to return it to my friend).

In the end, it’s not just about killing the hum—it’s about keeping history alive while sneaking in a little modern wizardry.

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Safety Disclaimer: Tube radios run on high voltages (often 300V+) that can stay stored in capacitors even after the radio is unplugged. If you don't know how to discharge a capacitor or work with mains voltage, please do some reading before you stick your hand in the chassis. I prefer my readers un-electrocuted.