Nuts and Volts - June 2015

cardboard tube and one of your new components.

Axial lead film capacitors work best here, but you can bend the leads of a radial component, and that's just fine. Slide the new cap into the tube, center it, and use a small dab from the heat gun to hold the part in position inside. Let the glue harden for a few seconds, then take your brown or beige polymer clay and push it into the sides, filling up the empty space and forming the end plugs of the capacitor.

Once you've filled in the ends, take the newly re-stuffed capacitor and give it a quick dip once or twice in your molten bee's wax (Photo 6). Let it dry for a few seconds and set aside.

You've re-stuffed a capacitor! Repeat for the rest of the caps in your radio, and you'll have a new set (Photo 7).

Re-stuffing the electrolytic capacitors is a little harder. Electrolytic capacitors are commonly found in cans above the chassis due to their size back in the day. Some people remove these cans, drill the case open just above where it mounts, extract the guts, and bundle up new electrolytic capacitors inside an insulator before gluing and taping the assembly back together. It's messy and frankly, in my opinion, it's tough to make it look good. Dealing with those hassles isn't an issue for the DeWald, though. It's missing its can capacitor, and there's a set of modern electrolytics instead.

Here, I'm going to fake it a little bit. The radio only needs to really look period correct at first glance, and modern electrolytics are so much smaller than they used to be. I found a slightly larger shell of an old paper capacitor which will fit a pair of 22 µf 450V electrolytic capacitors inside its diameter (back to back), with just a tiny bit of room to spare.

For this one, I gutted the old capacitor, then slid both electrolytics in. Now, there's a paper capacitor with two leads coming out of each end. It's not quite historically accurate, but it looks good at first glance (Photo 8).

Down to Business

Armed with a new set of “vintage” capacitors, it's time to swap out the components. Just cut and replace! Try and get the new capacitors as physically close to the position of the old capacitors as possible. Lead dress — the arrangement of the components and wires — is a big deal in radios this old, and component positions which differ radically from when it was built can cause problems like interference, feedback, and squealing when it's powered up (Photo 9). Sometimes radios like this are built in layers, and you have to remove some top components to get to the ones below them. I use an alligator clip jumper wire on each end of the component I've temporarily bent out of the way to make sure I don't lose my place while working on the deeper layers. Then, I come back and replace the jumper placeholder. I did end up extending some leads for the new "electrolytic" capacitors I installed, using leftover cloth covered wiring from another project to preserve the appearance (Photo 10).

While in there, I spot-checked the resistors in the radio. Resistors were made of a molded carbon compound back then, and as they age and absorb moisture from the