Thursday, May 21, 2020

The Smell of Burning Solder in the Morning

One of the things I like to tinker with is electronics.

Yes, I used to listen to shortwave radio back in the day, but these days old stations such as the BBC, Radio Nederland, and Radio Deutche Welle either no longer broadcast at all or broadcast to other parts of the world, not North America.

That doesn't mean that the itch to smell burning solder* ever really fades from someone who likes nothing more than to crack open an old radio and see what's inside.

Over a decade ago, I'd acquired a 1970s era Sony AM/FM radio for my son so he'd have a radio in his room. At the time he liked to have some music on overnight while he slept, and a radio like this one:

Sony ICF-9650W, from

for just a couple of bucks at a yard sale was pretty much a no brainer. Nice and solid feel, with only a couple of knobs and a single switch for small hands to play with, it was fairly kid proof.

So, for several years it stayed in his room until he acquired a modern boom box, complete with Bluetooth, and I relocated the old radio to the garage where I'd blast local stations when I was out working there.

The past several months, however, I'd noticed that the radio frequency would drift a bit, and the sound quality was degrading, so I figured it was time to crack open the radio and see if any of the parts needed replacement.

Well, this is what it's supposed to look like:

Again, from,
because my pic looked pretty lousy.
There's actually two more circuit
boards underneath the main one.

But instead I found quite a bit of corrosion coming from leaking capacitors.

See the two cylinders? Ignore the
dust and you can see the corrosion
at the bottom. It was even on the red
wire next to it.

So, once I found a schematic online I realized I had my work cut out for me. Sure, it wasn't going to be as exhausting as working on a classic 70s era receiver, but the circuit board design did not make it easy to access without taking apart and unsoldering several parts. But with the schematic I had a parts listing, so off to Mouser Electronics (yes, that's the name of the online store) to order a bunch of replacement electrolytic capacitors.

The caps arrived on Monday, so I took the better part of all of my spare time on Monday night and Tuesday pulling apart the radio and replacing all of the caps on the board. I probably didn't have to do so, but given that the radio was 42 years old I wasn't going to risk it.

I also had a hard deadline of finishing this before dinner on Wednesday, because I was using the kitchen table as my mad scientists' lab.

Still, I was on quite a high, tinkering with stuff I'd not touched in at least a decade or more.

I finished my work around 6 PM, spent about 20 minutes putting everything back together, and then fired it up.


I unplugged the radio, checked to make sure nothing was obviously wrong, and tried again.

Still nothing.

Muttering a few choice curses, I began checking to see if there was something fried on the board.

Yep, there was: all four diodes used in converting the power from AC to DC on the circuit board had blown. If you look at the second pic above, you can see that little stretch of parts in the bottom center that are covered in some tan goop; the green cylinders are ceramic capacitors that hardly ever are damaged, but the tiny black cylinders are the diodes that blew.
The good news is that their replacements (the originals are no longer made) only cost something like $0.04 or $0.10 each. The bad news is that I have no direct way of knowing if they blew because of something I did (which is likely) without more test equipment than what I have.** So I could simply buy a bunch of replacement parts once more, but I should also go over in detail everything that was replaced to make sure I didn't do something stupid.

And that --right now, anyway-- is something I don't have time for.

So I've got a torn apart radio sitting in my garage, taunting me every time I see it.

But I've not given up. Not yet. I'll get you, my pretty!

*and the occasional burning flesh accompaniment.

**I do have a digital multimeter, but I don't have the ability to check capacitors or signals or whatnot.
And I'm pretty sure my wife would not be pleased if I decided I needed an oscilloscope.

EtA: replaced the links with copies. For some reason the links broke some hours later.


  1. Clearly you need an oscilloscope :P

    I am always a little astonished and still interested in this radio stuff because while a lot of the stations were technically still around when I grew up, nobody I knew was listening to anything but local VHF stations (in the int'l FM spectrum), despite most of our radios still being able to do HF, at least I think so. I think the first time I even heard about Deutsche Welle was in the late 90s. But I guess I wasn't really so much into radio stuff as a kid and preferred to listen to music I liked over taking apart radios, and then computers happened...

    1. My interested in electronics started early, when I nearly killed myself by sticking in battery wires for a toy into a power outlet thinking "the outlet would make the toy work". To both save my life and keep me from asking for a chemistry set (my parents were afraid I'd blow up the house), I got one of those 150-in-1 electronics kits that you could use to make all sorts of simple circuits, including an AM and FM radio, but beyond that I never really wanted to "fix" radios and other items until I took classes in analog and digital electronics at university as part of my major.

      Shortwave started much later while I was at university, when I discovered an old 1940's era shortwave radio in the lab I worked in. I powered it up and attached a wire, and the first station I pulled in was the BBC World Service. Then, shortly after, the fall of the Berlin Wall happened and I was listening to Deutche Welle's live broadcasts as it was going on. That entire school year, things were happening overseas rapidly and the only way to keep up was by listening to shortwave broadcasts.

      That began to switch over in the First Gulf War when CNN was right on top of things as the war began. Shortwave supplemented the coverage, but television's on the spot coverage of a war was completely different than what happened in Vietnam or the Falkland Islands.

      Shortwave was also important during the attempted coup of Gorbachev, when Radio Moscow suddenly began broadcasting the facts on the ground in defiance of the Politburo.

      After those times, well, the internet took over.

      But to circle back, if I were born about 5 years later I'd probably not be interested in shortwave at all, because most radios from the 1970s on up in the US don't have the HF band.