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WARNING!

NO GUARANTEES! DO AT YOUR OWN RISK!

This page describes activities which can be hazardous, and which have many things which are totally outside my control. Don't blame me for your problems! You assume all risks if you partake in this activity.

Background

In the June, 2013 issue of Nuts And Volts magazine, someone submitted a question to the "Reader-to-Reader TechForum" on salvaging parts from old electronics equipment. Paraaphrasing what the poster asked: whether it's generally worthwhile, what kinds of old equipment contains the most rewarding, and whether there are parts that deteriorate. Although I've submitted a response, I have a lot more to say than I could reasonably put into that media, so I put this together.

The short answer: Ripping into old equipment that was destined for for the landfill can be fun, educational, and, sometimes, yield some potentially useful parts. There are even aspects of it that many wouldn't think of who haven't done it. However, you also need to be aware that there are hazards, but being aware of them, and how to avoid them, can keep you safe.

Safety

The first thing you should always consider is safety. Even the best parts aren't worth becoming a client at the morgue, or even at the nearest urgent care center.

Of course, before tearing into a just obtained piece of "junked" equipment, I trust you know enough to make absolutely sure it's not plugged in, and you'll remove any batteries before going any further.

Besides this, any device which has (or should I say, "had") high voltages inside needs to be treated with respect, especially if you don't have a lot of experience. Equipment such as old televisions or computer monitors that have CRTs (picture tubes) can have several thousand volts while operating. Some components can store potentially dangerous voltages for very long times.

But there is some good news: it's easy, and cheap, to make sure any such high voltages are discharged. Here's how:

Make a Chicken Stick

Although it has some more "politically correct" names, the most common is "chicken stick" (said lovingly) for a device used to safely discharge stored voltages. What it amounts to is a wooden or plastic stick about 18 to 24 inches (or 0.5m to 0.75m) long (or even a little longer). It has to have an electrically conductive (pronounced "metal") tip, closely connected to a resistor that is typically in the range of 10K Ω (10,000 ohms) to about 100K Ω (100,000 ohms). (The resistor can be any resistor rated 1/4 watt or more.) The other end of this resistor is then connected to a piece of insulated flexible wire, usually about 2 to 3 feet long (or 0.75m to about 1m) long. Finally, the far end of the wire has an aligator clip on it. You can easily build one yourself – if you don't have the parts already, a quick trip to the nearest hardware store to get a dowel (3/8 inch to 1/2 inch is a good choice), and the nearest Radio Shack store for the resistor (buying the wire and aligator clip at either store) will yield the parts. If you stop by McDonald's® on that trip, you'll almost certainly spend more on lunch than you will on your chicken stick. Oh, you'll also need a couple of nylon zip ties or some electrical tape, and probably a soldering iron and some solder, but I hope you've already gotten far enough into the hobby to have those.

One lead of the resistor can serve as the metal probe at the end of your chicken stick, though if you use it a lot, you might eventually want to substitute something a bit more substantial. By the way, "pointy" is a good thing for this probe, though I won't go into the physics as to why it is.

Once you've soldered the wire to the resistor, attach the resistor to the rod so that the probe sticks out beyond the end of the rod. Make sure it's firmly attached, using either a zip tie or some electrical tape. Then attach the wire near the resistor, say an inch or so (2 or 3cm) away from the resistor, to the rod, again making sure the attachment is strong. Once you've soldered the aligator clip to the loose end of the wire, your chicken stick is complete.

Using Your Chicken Stick

Once you've double checked again that the object of your tender attentions is not plugged in, you need to get into the case, but more about that a little later. If your piece of equipment is housed in a metal case, then likely it is grounded to the case. If it's not, see if the power cord has a three prong plug -- if so, we'll use that. As a last resort, see if there's something big and metalic on the circuit board.

Thumb in the belt!

Hook one thumb (I'll leave it up to you which thumb) into your belt behind your back, and use the other hand to connect the aligator clip on your chicken stick to the best ground in the gadget you're working on. (To be electrocuted, electricity has to flow through your heart. If you hook one thumb in your belt behind you, then electricity can't flow through one hand, through your heart, and out through the other hand.) While the thumb in the belt can protect you from electrocution, you can still get a nasty shock, so be careful.

Once you have your chicken stick connected to something metalic, hold it by the end that's away from the probe end, and use it to touch each terminal of every component in the circuit. You can use the rule of thumb that if it's a big part, hold the probe on its terminals for several seconds. If the circuit is known to have high voltage, make it more than just a few seconds. If yoou're a beginner, and aren't familiar with a lot of electronics, go over the circuit several times to make sure you've touched every pin several times. Then go have a cup of coffee, or some similar other activity for at least a few minutes, then go over the circuit again with the chicken stick. (The reason why is that some types of capacitors can, in essence, regenerate a voltage over a few minutes.)

What Next

Every piece of electronic equipment is going to be different. One of the best things that you can gain by disecting a lot of equipment is a good idea of what's inside of different types and some notion of what makes it tick. In general, I'd say that this knowledge is probably more valuable than any of the parts you might find.

As I mentioned, every piece of equipment is different, but your first challenge is to get inside (after you've confirmed it is NOT plugged in). Look it over thoroughly. If there are screws, you're probably in luck. You have a fairly good chance of simply unscrewing them and getting into the case. Remember "righty tighty, lefty loosey". If you've taken out all the screws you can find and the case doesn't come apart, rub your thumb nail over any labels – a favorite trick is to hide a key screw under a label. And if that doesn't help, take off any rubber feet, as often screws are hidden under them. If it's a plastic case, look for small inserts that hide screws. Sometimes plastic cases are snapped together. If all else fails, go ahead and apply force and destroy the case, but it's best to try to salvage the case if possible.

I suggest that you also practice identifying what each component on the circuit board is. I've been doing electronics both as a hobbyist and as a professional for over 45 years, and I still get stumped by some parts I see on boards, so don't feel bad if you don't know what everything is.

After you've identified some of the parts, or can make a guess about what some parts are, it might be worth looking at some of the online catalogs to find similar parts. (See my Sources for Parts & Supplies section for some links.) This will help you get an idea of whether or not something is worth salvaging.

There's another thing that you can do with some salvaged printed circuit boards that you might not think of: Practice getting components off the printed circuit board without damaging the board. Although the boards in question are of virtually no value, this is a skill that will eventually come in handy. Eventually when you're doing electronics you'll need to change out one or more parts that are soldered to circuit boards, whether you're trying to get a board of your own design to work, troubleshoot a board you've just built from a kit, or are trying to fix your friend's failed gadget. It is very easy to destroy a printed circuit board when trying to get a part off — so it's much better to practice (a lot!) on boards that are already scrap.

There are lots of different parts that you may run into in a particular piece of salvaged equipment. Here's a partial list that you might run into with some comments on each, in no particular order:

Power cords
When you're first starting to salvage equipment, the power cord is a tempting target. If it's in good shape, go ahead. If you can clip it off inside the case and get the strain relief out too without a lot of trouble, so much the better. The extra inch or so you might get by desoldering it rather than applying the wire cutters probably is not worth the effort — go ahead an cut it.

Be aware that if the piece of equipment is particularly old, or has been exposed to high temperatures or other adverse conditions, the insulation may have deteriorated. Inspect it carefully.

Knobs
Some pieces of equipment can yeild some nice knobs. Buying new knobs can be expensive, and finding nice ones can be difficult.

Most knobs will just pull off, others will require a small screwdriver or hex key to loosen a set screw.

Switches
Look for switches that can be gotten out reasonably easily. Some, though, just won't be worth the effort.

Potentiometers
If the object of your attentions is the sort that will have a volume control, you'll likely find a potentiometer behind it. These can be useful for a lot of things, and buying new ones can cost a couple bucks each.

Sometimes you'll also find linear pots (i.e., "slide controls"). These can frequently be worth salvaging.

Fuse holders
Panel mounted fuse holders are generally worth the effort to get out. Those that are mounted to PC boards, though, generally aren't.

But grab the fuse, either way. Use your ohm meter to check ot see if it's blown, and if not, stick it in your "junk box" as it may save a trip to the store to buy one sometime.

Resistors
Small resistors are generallly not worth bothering with unless they happen to have very long leads that you can clip near where they are connected to something else. Large, high power resistors may be another matter. If the resistor has lead wires as part of it, they're only worth grabbing if the leads are reasonably long. But if you run across a power resistor that has solder lugs on it, it's probably worth keeping.

At one time, carbon composition resistors were the most common type. However, many folks call them "carbon decomposition" resistors, as even if they've just lain in a drawer for 15 years or so, they'll be well outside marked tollerances. More modern types of resistors are more stable, and I'd expect a wire-wound resistor from before World War II to still be in tollerance.

Capacitors
Today most capacitors are soldered into circuit boards with fairly short leads. This generally makes them not worth bothering with. If you happen across some that have longer leads, it still might not be worth the effort. Many caps use somewhat cryptic markings.

Be aware that electrolytic caps can deteriorate with age. Most other types of capacitors are fairly stable.

Be very careful extracting capacitors, as there are effects that a capacitor can sometimes "recover" a charge on its own. If it's a 5 volt cap, it's not soemthing to worry about, but if it's a couple thousand volts, be careful.

Variable capacitors
Older radios that were not digitally tuned, and some other equipment, used variable capacitors to adjust the frequency (and sometimes other operating parameters). Learn to identify what type it is. Air variable capacitors (that is, ones that use air to insulate between adjacent pairs of plates rather than some other material) are valuable, and if you find one, grab it.

Transformers
There are many types of transformers. Some equipment will have power transformers (ones that transforms 110 VAC to something else, usually lower). If these can be had with reasonable leads, they're worth keeping. It's probably worthwhile for you to rip a couple of these apart, especially if you got them for free.

Old TVs (ones with picture tubes) usually have something called a flyback transformer. This device generated the high voltage to operate the picture tube, usually several thousand volts. They do not connect directly to the AC line — they usually are driven by the roughly 15kHz of the horizontal sweep, with the very steep flyback portion of that signal actually generating the high voltage. Thus the name flyback transformer. These are always in high voltage circuits, so unless you know what you're doing, REALLY know what you're doing, they're best left alone.

Many older circuits, such as radios, have several small transformers. These include small audio transformers, radio frequency or RF transformers, and intermediate frequency or IF transformers. They can be critical to older circuit designs, but aren't used often in more modern circuits.

Tubes
You may come across a piece of equipment that has a bunch of vacuum tubes inside. If you can positively identify it as being from the 1960s, it probably is a good candidate for salvaging. If you even think it might be older than that, though, you may be better off leaving it intact and finding a collector of antique electronics who may want to buy it from you.

If you do salvage a tube type piece of equipment, be aware that tubes require a minimum of about 80 volts to function, and many tubes require a lot more than that. So be generous with using the chicken stick!

Pull all of the tubes out of their sockets (although you may not be interested in using them yourself, collectors will want them), and be sure to salvage the sockets, too.

Wires
Once in a while you may run into a piece of equipment with some wires running around the inside. If the insulation on these wires is good, and they are longer than about 3 inches, clip them out and keep them in your "junk box". There are times when it's really nice to have a few peices of wire handy.

Hardware
Screws, nuts, bolts, washers, feet, springs, and other little bits of miscellaneous hardware are generally worth keeping. Some equipment can yeild a lot more such things than other peices of equipment.

Some things, like old VCRs, have a lot of interesting mechanical tidbits.

Motors
Some things contain motors. These can be a lot of fun, especially if you can identify what type of motor it is and the ratings.

Cases
Don't overlook the case that your treasure is in. Project cases can be expensive. (When I first started in this hobby, the case for the project would often cost more than the parts inside it. I built several projects using empty tin cans as cases.)

If you find a rectangular metal case, be sure to keep it. You can alwas replace the front panel with something. A piece of sheet metal, or a piece of flat plastic, or thin plywood, can give you new front (and sometimes back) panels at a lot less cost than a brand new case.

Circuit boards
In general, the circuit boards themselves aren't worth a lot, though they can be good for practicing soldering and desoldering techniques.

If you do happen to strip all the parts off a PC board, you might be able to use it in the future as a work surface for soldering.

Integrated circuits
Unfortunately, these can often be hard to identify exactly what they are, and unless you happen to have some rather expensive equipment, they're quite hard to get off the circuit boards without damaging the ICs. Since ICs are easily damaged, they're probably not really worth trying to salvage.

Surface mount parts
With a bit of practice, and using two soldering irons, it is often possible to get many surface mount parts off the circuit board. The problem is that most of the surface mount parts are so inexpensive that they're not worth bothering with. Surface mount capacitors especially fall into this category, as they are rarely marked with any indication as to value. Other types of components do have markings though they often take some effort to decode.

Computer disk drives
Disk drives deserve a special mention. Although there is NO WAY you're going to get one back together (it would have to happen in a cleanroom), if you have a disk which you're certain is of no further use, go ahead and tear it apart. It is very educational (and fun) to see how the things are actually put together.

Connectors
There are a lot of connectors that I wouldn't bother salvaging. If I can get two mating connectors, with at least a couple of inches of cable on each so I can splice into it, maybe.

On the other hand, there are a couple of radio connectors that I happen to have the special tools to get the pins out of them that I will always take, but those are rare.

Transistors, diodes, and similar
Most of the so-called "discrete" semiconductors are not worth bothering with as far as salvage parts, at least in my humble opinion. However, large power transistors and similar parts, especially if marked with part numbers, may be worth gathering.

That said, when you're first starting out, if you find small transistors that are clearly marked as to their part number, and have fairly long leads, you can grab them to play with. If you "let the smoke out" of something you got for free, who cares?

Transistors usually don't deteriorate much with age, though they are susceptible to heat damage as well as both electrostatic damage and damage from overloads.

Speakers
Many pieces of equipment include speakers. These are almost always worth salvaging. If you touch an ohm meter's leads to the terminals, small speakers will emit a click, though not clicking isn't a sure sign that the speaker doesn't work. The resistance of most speakers is very low. You might also run into piezo buzzers that look similar to speakers. These have a tendancy to have a large DC resistance.

Even if a speaker doesn't work, it can often yield a magnet that can be interesting, as well as some incredibly thin magnet wire.

Heat syncs
Heat syncs, which are usually big chunks of aluminum, often with fins. These are almost always worth grabbing. They can easily be repurposed for another life. New ones can be relatively expensive, and somewhat hard to find.


I've by no means covered all of the possible parts you may run into, but hopefully I've whetted your appetite for at least looking into old electronics.

Once you've stripped all the parts you want, the best thing to do with the leftovers is to try to get them into the hands of an organization that will recycle them. Most electronics contain small amounts of gold, and even with today's gold prices, it's probably less than a dollar's worth. However, when crushed, old electronics have a significantly higher concentration of gold than most ores that come out of the ground. And there are other elements that can be recovered, such as tantalum and neodymium, as well as others. And, to boot, you may keep some lead out of the landfill. They probably won't pay you anything, but hopefully they won't charge you for accepting it.

In summary, enjoy ripping apart salvaged equipment. You may find some useful parts, but you'll almost certainly find some useful knowledge, as some pieces ofequipment provide examples of excellent design and construction, and others will provide examples at the other end of the spectrum.

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This screen last updated: 12-Jun-2013

Copyright © 2013 by Clark Jones