Starting in the ’50s, they’d figured out how to start miniaturizing components. “Couplets” and “printed electric circuits” started showing up in equipment around then. These components were combinations of several resistors and capacitors in a single package.
Like most components from that era, they do start to go bad over time – although you can’t exactly run down to the local Radio Shack and buy a Centralab PC-191 or a Sprague TC-24 anymore.
So, sometimes it’s necessary to roll your own.
Those two boards replace a set of tone control circuits in the EICO HF-81 amplifier. A little bit bigger when made with discrete components, but not too bad! These will be much more reliable, too.
Enterprising French amateur Claude Paillard , F2FO, creates beautiful modern vacuum tubes by hand in his shop. These would be effective as an 01A replacement or similar in an early radio.
It’s a real work of art. Check it out!
Fred Clift wrote over on his blog about why it’s worthwhile to pick a more expensive multimeter. He’s comparing a $200 Fluke to a $6 Harbor Freight multimeter, which really is a no-brainer. I’m not sure the Harbor Freight model would be safe to use on any of the higher range measurements with those whispy, poorly insulated test leads.
I use a few mid-grade meters for basic bench measurements and was interested to see how they compare with the Fluke 87V and the Cen-Tech from Harbor Freight.
I use the Mastech MS8268 meter which I recommended in my “Getting Started with Basic Tools” post. It’s durable, rugged, and costs only $25. Really, it’s about what I expected to find. As you go down in quality you lose accuracy, but the Mastech meter has all the same functions as the Fluke – just not quite as tight.
The Fluke does have some cool features that Fred picks out. It will tell you min/max/average over an interval, faster continuity beeps to quickly check a strip of connections, and a higher voltage continuity test that can actually light up an LED. Otherwise, though, the Mastech has the same basic capabilities including 200 kHz frequency measurements. I’ve been able to use that in a pinch as a signal tracer – set the meter’s range to measure frequency, and probe the stages of an audio amplifier. Meter shows the tone? Move on to the next stage.
A lot of applications don’t need 0.05% accuracy on a DC voltage reading, so I stand by my recommendation of the Mastech as a “good enough” meter for most hobby work and vintage equipment repairs. There’s definitely situations where it’s worth it to spend a bit more, though.
A few people have asked me variations of “What tools do I need to fix my first radio?”, “What do I need to put together this soldering kit?”, and such. It’s not as simple as you might think. There’s a lot of equipment out there, and if you’re starting out it’s not always easy to tell what’s good from what’s garbage. Picking the wrong tool for the job will give you a frustrating repair experience at best, or could even damage your project.
You do only need a few things to get started: a soldering iron, a multimeter, a wire clipper, a wire stripper, and some basic safety gear. If you’re a casual hobbyist who will do a few projects a year, you can get started for under $100. If you’ll be working on electronics a little more often than that, you’ll want to spend a little more for more durable tools, but they’re still pretty affordable.
Below are some tools I’ve selected which will help you get through your first project and then some:
Probably the most important item on this list, you’ll use the soldering iron to make connections between wires and components. You need to make sure you get an iron that will be durable enough, and produce enough heat, to quickly melt the solder and heat up joints without taking too long and causing “heat soak” which can damage other near-by components you’re not actively working on. While it might seem counter-intuitive, too small of a soldering iron is actually a bigger problem than too big! I recommend a soldering iron around 50W for most hobbyist applications. Stay away from any of the “cold heat” soldering tools which aren’t very effective for this kind of work, and stay away from any gas-powered soldering iron as those are more suited for plumbing or off-the-grid work.
For electronics repair, you can get started with a no-frills soldering iron for under $10 (left). I’d recommend spending a little more, though, to gain temperature control and easier replacement parts if you need a new tip or heating element. For about $20, you can upgrade to a Velleman 50W adjustable soldering station (center) which has a handy cleaning pad and soldering iron holder built in. If you’ve got deeper pockets, Hakko makes excellent professional-grade soldering products like the FX888D digital soldering station (right) which has a digital temperature control, and you can get dozens of different size and shape tips and replacement parts very easily. I use the Hakko FX888D in my shop, and it’s fantastic.
You’re also going to want the right kind of solder. Rosin Core Solder is the right kind for electronics and includes flux inside for a good connection. There’s new RoHS-compliant (“lead free”) solder out there, but personally I find it’s more difficult to work with. Wash your hands after soldering and you’ll be fine using traditional lead solder, like this basic 60/4o Electrical Repair Solder (left). Standard tin/lead solder comes in a several varieties; 60/40 and 63/37 are pretty common and there’s not a major difference. If you’re going to be doing work on sensitive audio or RF circuits, some kinds of solder can offer a little better performance. Silver-bearing solder forms joints with a lower resistance; tube radios won’t really benefit but some high-end vintage hi-fi gear can benefit. Tenma makes a very nice 96.5% tin, 3% silver, 0.5% copper solder (right). Be sure never to use acid-core solder as you’ll damage your device, acid-core solder is only suitable for plumbing.
You’ll use the multimeter to make a few circuit tests, including checking for the correct voltage at a few points in the circuit, and for measuring the value of resistors. A homeowner’s multimeter isn’t a good choice for these repairs, but even an inexpensive digital multimeter will be more accurate than most of the tools in a repair shop back in the day. At about $25, the pictured (left) MASTECH AC/DC Auto/Manual Range Digital Multimeter will measure AC and DC volts up to a higher range than you’ll ever likely need. It also can measure current, resistance, test diodes and continuity with a buzzer (useful for checking coils!), roughly measure the value of capacitors, and do some basic frequency measurements. Sure, it’s no Fluke (right) but it’ll get the job done just fine. A meter very similar to the MASTECH is my everyday go-to meter that I use during all but the most precise measurements, and it’s never let me down.
You’ll need to cut old component leads and cut wires down to size when doing repairs. A set of flush-cut wire clippers makes short work of this, and they’ll last longer and won’t get the cutting edges nicked up as if you tried to use a general cutting tool like a pair of household scissors. They’re very inexpensive – under $5 – and come in handy around the house as well as in the workshop.
Right along with the wire clippers, you’ll need to prepare old and new wiring for soldering by removing the insulation. An adjustable pair of wire strippers is critical so you remove the insulation without damaging the wires underneath. At the low end, around $5 will get you a set of TEKTON continuously variable wire strippers (left) with an adjustment nut, and they have a cutting edge as well. This is okay if you have only one wire size, but it’s a bit annoying to adjust every time. I prefer wire strippers with their own sized guide holes. Moving up to around $20, you can pick up a nice Klein Tools wire stripper (center), or a Greenlee Communications wire stripper (right). I own the Greenlee and it’s got a comfortable grip and is very sharp and easy to use.
Soldering does produce some toxic fumes, and you’ll want to make sure you’re in a well ventilated area. Soldering indoors isn’t a big deal occasionally, but you don’t want to breathe in the smoke too often. If you can’t open a window, you can use a variety of smoke absorbing filters for your workbench. They start at about $35 for a smaller desktop model, suitable for light work, up through many hundreds of dollars for a professional fume extraction system like the Hakko FA-430 which Rain City Audio uses.
Sometimes molten solder can splash, or a piece of wire can go flying, and you’ll want to protect yourself. Safety glasses are highly recommended, and can be had for as low as $3 if you’re buying some of the other items. That’s a low price to pay for peace of mind! Some people like to use a surgical filtration mask while soldering as well, to help with residual fumes. They’re available for about $1 each in boxes of 20. I don’t use a mask, personally, but if you don’t want to spring for a fancy ventilation system and don’t have good airflow in your location, you might consider it.
A tip cleaner and debris catcher is also very handy for keeping your iron clean but isn’t strictly necessary. At a minimum, keep a damp kitchen sponge on hand with a scrubby side and use that to clean your tip after every few joints.
That’s all you’ll need to get started. If you get further into the hobby, or run into functional issues once you’ve finished replacing the needed components, you’ll also want a few pieces of test equipment. Look for my recommendations on hobby test gear for radio and electronics repair in a future article!
I stumbled across this blog while browsing recently and just had to share. It’s similar to this one with more focus on transistor radios: JM Radio, based out of Indonesia. The author has quite a collection of transistor radios he’s worked on over the years, and has a handful of parts and radios for sale to interested collectors and technicians.
The entire site does happen to be written in Indonesian, but the automatic translation does well enough to understand what’s going on.
It’s a fun read, well worth dealing with the machine translation. There’s also some events write-ups and tech tips and tricks. Check it out!
Radio might be taken for granted here in the U.S., but in other parts of the world it’s still a vital link in receiving underground information in repressive regimes. This story out of North Korea from NK News shows just how important it is in some other parts of the world.
Doesn’t look like much, and apparently it was pretty tough to operate without a tuning dial and with such a small tuning knob on the front:
The radio therefore leaves users to depend totally on delicate hand skills to turn the manual module in micro-inches every time. NK News staff could, however, easily experience the frequency changing with slightest turn of the module either to the left or right.
That knob would be controlling the variable capacitor on the board, shown bottom left:
This is interesting. It’s clearly an adapted PCB from another device, which looks to have been modified with a few additional capacitors and other components on the front end and possibly the amplifier area. It’s tough to tell how much is in use for this modification, though. This might have been from a tunable radio smuggled in elsewhere and modified, or could have been a state authorized radio modified to tune a different frequency range.
It looks like two new coils are in place, which could correspond to an antenna and oscillator coil. These would definitely need to be replaced to change the tuning range of the radio. They could be coils to adjust an RF tuning range for two stages of an RF amplifier, though. It’s tough to tell from the circuit board the principle of operation of this radio – it could be a superheterodyne receiver, which would offer a bit better performance and would be able to tune the FM signals as well as AM/Shortwave, but it could also be a tuned radio frequency detector which would be able to pick up the AM and Shortwave bands only in most circumstances.
The superhet would leak a low-level oscillator signal that could potentially be picked up by counter-intelligence agents to determine if someone was listening to a prohibited broadcast (although the average law enforcement officer in North Korea might not be sophisticated enough to operate direction finding equipment to find such a receiver) but would be able to pick up FM transmissions as well. The TRF type radio wouldn’t leak a local oscillator signal but might not be able to effectively decode an FM transmission depending on its construction. Really, it’s likely there are a variety of underground radios with different capabilities depending on what can be scrapped together at the time.
This all goes to show that hacking circuits is more than just a hobby – it can have real, life-changing implications for people in other situations using the same skills. That’s pretty powerful.
For more about this particular radio, visit the Original Article at NK News.
For more about underground information access in North Korea in general, The Atlantic has a great piece in their April 2011 issue.
Rain City Audio is proud to announce a new product offering: capacitor repair kits for the Westinghouse H-126 Little Jewel / “Refrigerator” Antique Radio!
This repair kit contains the most commonly needed parts to refurbish your Westinghouse H-126 Little Jewel / Refrigerator radio. You’ll receive 13 modern, high quality replacement film and electrolytic capacitors to bring your radio up to full performance. Take the guesswork out of fixing your own collectible model of Little Jewel, and save the hassle of using a parts site like Digi-Key, and order a kitted set of parts that’s ready to replace.
Included in this kit:
1 x 0.001 uF (You’ll receive 0.001 uF)
1 x 0.2 uF (You’ll receive 0.22 uF)
2 x 0.04 uF (You’ll receive 0.047 uF)
1 x 0.005 uF (You’ll receive 0.0047 uF)
1 x 0.025 uF (You’ll receive 0.022 uF)
2 x 0.01 uF (You’ll receive 0.01 uF)
1 x 0.1 uF (You’ll receive 0.1 uF)
1 x 0.1 uF (You’ll receive an X1Y2 Safety Capacitor to replace the across-the-line RFI suppression capacitor.)
1 x 20 uF 50V Electrolytic (You’ll receive 22 uF 50V)
2 x 50 uF 450V Electrolytic (You’ll receive 47 uF 450V)