Thursday, October 8, 2009

How to Fix Your Old Radio (and get fat while you're at it!)

Natalie and I picked up a mid-century coffee table/radio/record player combo a few months ago. When I turned the radio on, it wasn't broken per se, but there was a loud buzzing/humming sound. As I've learned from my research, this is called "the 60hz hum." I may have made up the official phrase, but I think I've earned that authority from what I've accomplished. The electricity from the power lines is delivered in what's called alternating current, or AC-- which, for we non-electricians, means that the electricity looks something like the picture to the right.

Most electronics depend on direct current, or DC-- which is a constant flow of the same amount of energy. So, one way to convert AC power to something closer to DC power is through the use of capacitors. (If you'd like to learn a little more about this, have a look at this video, it's actually quite interesting.) If a capacitor fails, then it just sends through the alternating current and the effect on a set of speakers is a low pitched humming or buzzing sound.

Well, you ask, how might one solve this problem, oh wise electronics expert? An anonymous reader shared a bit of his or her expertise in the following comment:

If you're handy with a soldering pencil ($10 at radio shack, get a 30-watt), you can easily replace the capacitors yourself. There are many videos on youtube that will guide you through it, as well as dozens of experts on who will help you with the restoration. New parts are easy to obtain via The hum is indicative of a vacuum tube set -- it's important to replace these capacitors soon as running the set with the aging parts will potentially fail as a "short circuit" causing firworks and potentially taking out irreplacable coils with it. Excellent find any way you look at it!

oops one more thing on the capacitor replacement. Choosing the new parts is easy -- just look for paper/wax "tootsie roll" looking parts on the chassis. They'll have numbers on them like ".01 uF / 350V". the uF indicates the size, the V indicates the voltage rating. Just get the identical part values (both numbers should match on the replacement) from The "hum" you hear is the large filter caps, which look like a hair roller in a metal or cardboard can (usually something like "47uF / 450V", a larger number than above). This is a common age-related problem. Don't be afraid to learn! I taught myself by reading and have restored many old radios over the years!
Thank you so much for this information! So I got right on the problem and did a bit more research on my own. First things first, I needed to crack open the ol' radio.

Behold, the much coveted wax tootsie roll (which doesn't sound particularly delicious...)! I've found over the years of trying to fix (i.e. tearing stuff apart) is that you will not learn anything if you're afraid to break it. Step 1 in my case: recklessly take a pair of scissors to the wax tootsie roll.

Continuing to follow the advise from our wonderful reader, I took a gander at the roll and saw 6 bits of important information-- this tootsie roll contains 3 capacitors, all with different ratings. 100MFD, 300VDC on red, 75VDC, 300VDC on blue, and 70MDF, 25VDC on green. uF (which means microfarad... which means...I don't think we need to explore this any further) and MFD mean the same thing and VDC (Voltage Direct Current) and "V" mean the same thing, so if you're looking for new parts, just know those are interchangeable.

So, just search those numbers and you're all set, right? Not quite. Capacitors have a lot of possible values and I wasn't able to find an exact match. Never fear, here is a website that tells you what's an acceptable range for replacement.

So, I then had to wait (very impatiently) for the new parts to arrive. Here is how I waited...

Grilled Ribeye Sirloin Steak with Onion-Blue Cheese Sauce, sweet potatoes (an impulse decision by yours truly... they just sounded good), a salad with homemade orange oil and vinegar dressing, pineapple and avocado (which, if pronounced with a Spanish accent, sounds strikingly similar to "have a cow").

That's right-- we used a whole stick of butter on dinner. It was worth every calorie. Unbelievably good.

Hi, I'm being cute. Can I have some?

He got a little bite from his food bowl. How could we resist? (P.S. How cliché am I? Blog? Check. Pictures of your animal? Check. Captions on photos of your dog with what you think they say? Check. Oh dear, I've become what I hated.)

The new capacitors came in today and I got to work immediately.

 Yes. It's sloppy-- even looks like I planted a tiny bomb (aww, cute little guy). I forgot how terrible I am at soldering.

But-- you won't be able to see the sloppy job. Instead, enjoy the beautiful glowing ruby-shaped LED.

It's alive! No more buzz. (Note: See "FM Stereo"? Looks like this puts our unit somewhere around the early 1960's as FM Stereo system wasn't approved by the FCC until 1961)

And now that we're all tuckered out, it's time to get some sleep. We let it all hang out here on Chadwell Drive.


Natalie said...

Yay! You even made what Reelee was thinking in Italics! =) That makes me so happy!

And I am craving one of those steaks. So amazing.

Kasey at Thrifty Little Blog said...

I'm so impressed by the DIY skills! For most people, the radio would have ended up in a landfill.

Anonymous said...

I'm the bloke that posted that information....I'm absolutely proud of your accomplishment! And what a good writeup!

By replacing all those wax/paper capacitors and checking the measured values of the resistors against the "stated" value (denoted by the color bands with a digital multimeter (they are a numeric coding system) you can return its performance to like-new sensetivity and sound. Sometimes they loose low bass or high treble as the components age. You'd be surprised how good they can really sound.

One more thing to consider -- if it doesn't already have one, add a fuse to the power cord under the chassis. You've replaced the most vulnerable part of the chain, but that small addition could protect the radio should age and time get the best of another part down the road.

Congratulations on your new-found skill!

Anonymous said...

OK so I seem to have this habit of posting in pairs....I'm still too lazy to get a "real" ID for posting.

The style of your house looked awfully similar to the ones in my neighborhood so I looked at your "about" page and realized you're local. I'm in downtown-ish Dallas. Feel free to shoot me an email if I can be of further help on your radio --

Cara said...