Many BEAM newbies report having difficulty identifying scavenged electronic devices.

Tracking down parts on the internet is possible. It takes some time to do. It takes some time to learn what numbers on the part to look for. It also takes some time to learn what to search for and how to search….

Here are some general strategies to use:

1. Identify the part before you unsolder it, because often you can get clues from the PCB (Printed Circuit Board). The label on the board may give a generic part number, or there may be other information you can use. There is a common shorthand: R = resistor, Q = transistor (I don't know why*), C = Capacitor, U = integrated circuit, L = coil. If the label beside a three-legged device says "Q17", you know it's a transistor. On a VCR board, for example, find the IR receiver, the one that reads the signal from the remote. Follow the trace from the IR receiver to an IC. This IC will probably decode the frequency signal from the remote. You might be able to use this chip along with the receiver as part of a robot that you can control with the remote. You will want to keep this IC and all the resistors and capacitors connected to it together. You might even saw out the chunk of PCB it's on. But don't do this until you have identified the chip and know where its input and output pins are!
2. Learn to read the codes on the component. A component label usually contains three things:

It takes some time and practice to learn how to read these.

The first letter F is in italics, and tells me the chip was manufactured by Fairchild. (A stylized 'M' is Motorola, a little map of Texas is Texas Instruments, ST is for Sanken; all the manufacturers have some little logo for their product). The rest of that first line is a "house" code that tells where and when it was manufactured. I really don't care about that. The next two lines tell that the chip is temperature rated for normal consumer use or higher (again, you can search the Fairchild site to learn exactly what these codes mean, but who cares). The "N" at the end says that it is a plastic dual inline package, or PDIP, but I already knew that because I've got it here in my hand....

I usually start with Google, though in this case I might try the Fairchild website first. Searching for the first number, FP0148AB, will give nothing useful. Searching for ALL of the second line probably won't produce much in a Google search, but might give me what I want on the Fairchild site. The manufacturers site is generally a good place to look, if you can figure it out. A list of manufacturers is attached at the bottom.

Lopping off the letters at the back often leaves the right number, and if that fails lop off the first two characters and try again. So I would search first for "MM74HCT240N", then "MM74HCT240", then "74HCT240". If I strike out again, I might leave out some of the middle letters and just search for "74C240", "74HC240" and so on.

I generally search for the number and the words "datasheet" or "specification" because that usually turns up a .pdf (portable document file, to be read with Adobe Acrobat Reader) with information about the pinout and electrical characteristics. It takes practice and patience.

Here's a specific example that I dragged up from the workshop for this tutorial. I have been meaning to look this up for a while now. I think it came from a fax machine, or maybe a printer. It's a four-pin device in a T0-9 package, like a power transistor, on a beautiful little PCB with a four position jumper and a 20-pin header. I left it all together because it looks like a complete unit. I am pretty sure it's a programmable voltage regulator because it says on the pcb that the different jumper positions are for 3.3V, 3.45V, 3.6V, and 4.0V . Sometimes the label on the PCB is an aid to identification, but this one is simply labeled "U1" which doesn't help. Still, I have learned quite a bit just from studying the PCB.

Okay, the bottom line looks like a manufacturer's code showing time and place of manufacture. The chip is by Sharp, so I could start by looking for the Sharp website. A Google search for P030RV21 gives no results. I try "Sharp P030RV21", no results. I try "Sharp 30RV21" and learn that the device is a PQ30RV21--I misread that second digit as a zero. Dang, on the IC it sure looks like a zero! Anyway, I've got it identified and don't have to try anything with an "oh" instead of a "zero".

Google refers me to doom.com, a commercial datasheet service where I will have to subscribe and pay to get information. Nuts to that.

sharp-world.com/products/device/lineup/ data/pdf/datasheet/pq30rv1_e.pdf

You can see how within five minutes, despite a few false starts, I obtained the information I needed. Sometimes the process takes a lot longer and you need to persevere... I hope this walk-through has been of some help to you.

The meter will tell you whether the transistor is funtional or blown, type it as PNP or NPN, identify the base, emitter, and collector, and tell you the hfe (or 'gain' or 'amplification') of the transistor. (This will not help you with a lot of things that look like bipolar transistors but aren't. SCRs, voltage regulators, UJTs, FETs, and a whole bunch of other things can fool you, and the meter may not help because it will just tell you that your 3-legged device ain't working as a bipolar transistor. In these cases you have to do a web search.)

An alternative to a multimeter is a little $20 device that RadioShack used to sell, called a "component tester". See if you can track one down. It will tell you PNP/NPN and give the pinout but will not tell you the gain. It will also identify FETs and SCRs.

Here's a tip: you can often substitute any small-signal switching transistor in a BEAM circuit. Sometimes a "scavenged" transistor will actually work better than the 2N3904 (or whatever) usually used. Simply breadboard the circuit using a new 2N3904 (or whatever) then power down, replace the 3904 with another transistor, repower, and note any differences. But in order to do this with any success, you absolutely MUST know the type (NPN/PNP) and pinout (ebc and bce are common pinouts).