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Testers And Tools

The Clicktester, Handitester and Lightester are simple projects to make; you'll find them invaluable for trouble-shooting appliances

Here is the "Clicktester" wired but not assembled; the parts have been separated to show connections. The earphones, the single flashlight cell and the flexible test prods are connected in simple series.
 
All electrical appliances contain wire of L one sort or another, through which current flows to perform a variety of tasks. In the case of heating devices, such as ordinary lamps, irons, grills, coffee makers, etc., the wire is purposely designed to resist or impede the movement of electrons. The latter, in pushing their way through this resistance, develop considerable friction, the outward effect of which is the desired heat. The most commonly employed resistance wires are alloys: nickel chromium, nickel copper, nickel chromium iron, nickel iron, and manganese nickel, which are sold under dozens of different trade names.

For most other purposes it is desirable to have wire of low resistance. Soft copper is universally used because it is cheap and workable. Only silver has a lower resistance value, and for this reason the contacts and sometimes even the wire of certain high-grade instruments are silver-plated.
 
In low-resistance wire, electron movement is converted into useful mechanical movement through magnetic effects, as in the case of motors, bells and buzzers, and other items.

Obviously, the wire path must be continuous, or no current can flow. Because wires do burn out in normal service or from accidental short circuits, or break from physical abuse, the basic test to be made on an appliance suspected of being defective is a "continuity" check. Fortunately, this can be done easily and quickly with some very simple and inexpensive testers, which you can make yourself either from "junk box" parts or a prepared kit.

The "Cliclctester"

Consisting merely of an earphone, a single flashlight battery and a couple of pieces of wire, the "Clicktester" is entirely adequate for about 90% of all the troubleshooting you are likely to do on household electrical devices. Any single or double earphone intended for telephone or radio work will serve the purpose. Astronomical quantities of very sensitive military phones are kicking around the surplus stores, at a fraction of their real value. The radio mail order firms sell a perfectly suitable single phone for only 96 cents!

The two tip jacks for the earphone terminals are taped securely to the body of the flashlight cell. The   length   of  the   leads   with   the   test  prods  is   not critical; lamp cord between  12 and  18" is OK.

Check the condition of switches with Clicktester tapping the probes against terminal screws.

Is wiring in fan OK? A test with Clicktester will by give answer; no sound reveals an open circuit.
 
To facilitate connection to the end pins of the phone cord, you need two pin jacks, which cost 9 cents each; also two tip plugs, at 14 cents each, for use on the ends of two test wires or "probes." The latter can be any flexible insulated wire ... a section of lamp cord is fine . . . about a foot long. The battery can be of either the "C" or "D" size. One that is too run down for a flashlight might have enough juice left in it for a year of tester service.

Cut a piece of insulated wire about 3 inches long; solder one end to the bottom of the battery and the other to a tip jack. Solder one end of a probe wire to the top (center) connection of the battery. Solder one end of the second probe wire to the second tip jack. Tighten the free ends of the probes to the tip plugs. The latter do not require soldering. Push the bared end of the wire through a hole in the body of the plug and catch it under the threaded head nut. Tape the tip jacks individually with friction or Scotch electrical tape, and then tape the pair to the body of the battery. Push the tips of the phone cord into the jacks, and you're in business. It will probably take you longer to read this description of the Clicktester than to make the item.

With the phones resting on the table, touch the free probe ends together. You will hear a loud click when you make contact and again when you break it. With the probes pressed firmly together, you will hear nothing. Don't be afraid of the metal ends of the probes. You can touch them freely, as the 12 volts of the battery isn't enough to shock a gnat.

Using the Clicktester

In using the Clicktester, it is usually convenient to wear the phones, just to get them out of the way. Don't put them directly over your ears, but push them forward slightly. The clicks can be strong enough to be uncomfortable when they are sounding.

To illustrate a basic application of the Clicktester, let's try it on an ordinary switch. In the latter's off position, touching the probes to the connecting screws should produce no sound. Snap the arm to the on position and try again. This time you'll hear loud clicks as you tap the probes on the screws. These are the results you will obtain from a switch in normally good condition, but don't think that all switches respond that way. Because of failure of the internal spring or fusing of the contacts, a switch is likely to test either open (no clicks) or closed (clicks) with the arm in either the on or off setting.

The more wire in an appliance, the higher its resistance, relatively. You might therefore expect that the clicks will be weaker with a device like a fan or clock, for instance, than with a switch, which has practically no resistance. Actually, the difference is not very great, as you can readily tell by trying the Clicktester successively on an electric bulb, a fuse, a fan, an iron, a mixer, etc.

The Clicktester must not be used on parts or appliances connected to live circuits. The devices to be tested must be disconnected entirely. Observe the usual safety precaution of unscrewing the line fuse before touching the wires or terminals of any outlet. In the case of common appliances such as fans, mixers, air conditioners, irons, etc., it is, of course, only necessary to pull the line plug from the wall receptacle.

A device as simple as the Clicktester can be expected to have some limitations. The clicks indicate that the device under test has a continuous or closed circuit; however, the tester cannot distinguish between a normal low-resistance circuit and an extremely low resistance such as created by an internal short circuit or other abnormal condition. To do everything the Clicktester can do, and its missing 10% also, you need a measuring rather than an indicating instrument.

The "Handitester"

The Heathkit "Handitester," made especially for electrical trouble shooting, is such an instrument. A complete kit costs less than $15 and makes up into a professional-looking meter that will prove extremely useful not only for household appliances but also for the electrical system of a car and for the simpler elements of radio and even television receivers. Assembly and wiring are an evening's work. In a shiny black molded case, the completed tester stands only 6 by 3 by 2½ inches overall.

The Handitester is a combined voltmeter, ohmmeter and ammeter, all in one. The various functions are brought into play by means of a 12-position switch on the front panel. Connection between the tester and the circuit or device to be tested is made by flexible plug-in wires. One wire terminates in a spring clip, which is hooked to one terminal of the appliance; the other wire ends in a long insulated probe which is touched to the other terminal of the appliance.

These are parts for Handitester as furnished in complete kit form. Meter unit is part of front panel. Hand holds  three-deck  "function  switch."  represented on front panel by  control knob with pointer.

Inside view of completed Handitester. Battery on back of meter provides current for all resistance measurements. Wiring as seen here is compact

Instruments of the Handitester type are known generally as "VOM's," for "Volt-Ohm-Meter." They are available in a large variety of both kit and factory-assembled models, from mail-order firms and from electronic supply stores everywhere.

As a voltmeter, the Handitester has 10 ranges, five each on DC and AC. Some of their possibilities for checking and troubleshooting are listed on this and the following page for your information:

DC: 0 to 10 volt scale: flashlight, lantern, radio "A," and doorbell batteries; one-, two-and three-cell storage batteries.

0 to 30 volt scale: hearing aid and radio "B" batteries; six-cell storage batteries.

0 to 300 volt scale: larger radio "B" batteries; radio set "B" voltages.

0 to 1000 volt scale: electronic photoflash batteries; radio "B" voltages.

0 to 5000 volt scale: same as 1000 volt scale.

The   value   of   a   meter  shows   up   in   checking   a   switch   for   poor   contacts.   If   they   are   poor,   the meter reads  an  appreciable fraction  of  an  ohm;   if they are good, the needle bangs over to zero.
 
AC:

0 to 10 volt scale: some bell transformers.

0 to 30 volt scale: bell, toy train and house thermostat transformers. 0 to 300 volt scale: all two-wire, three-wire and four-wire power circuits. 0 to 1000 and 5000 volt scales:  not much application.

As an ohmmeter, the Handitester is used like the Clicktester for continuity checking, except that it actually measures the resistance of the appliance in ohms instead of only showing a closed or open circuit. The meter has two resistance ranges: "LO," with easily read figures between 0 and about 500 ohms; and "HI," 0 to 50,000 ohms. Most appliances have normal resistance values well below 500 ohms. About the only ones running higher are small electric clocks, which measure between about 700 and 1000 ohms.

Zeroing the Meter

If the Handitester is set for LO ohms and applied to the same switch used experimentally with the Clicktester, the two extreme ends of the scale will come into play. First touch the probes together and turn the "OHM ADJ" knob on the front panel until the needle swings all the way over to the right or O position; this step is called "zeroing the meter." Separate the probes and the needle will fall back to the left end of the scale. Now touch the probes to the switch terminals. With the arm "off," the Handitester needle will not move, showing the switch to be completely open. With the switch "on," the needle will bang over to O ohms, or the equivalent of a dead short circuit. This is normal, as a closed switch should offer no appreciable resistance to the flow of electrons through it. If its contacts become loose or dirty, a condition that shows up on the meter as a slight value of resistance definitely above the O line, it can become quite hot and waste a lot of energy.

Ohmmeter readings have some significance in trouble-shooting only if you know the normal resistance values of appliances and machines. In this connection it is extremely interesting and instructive to make quick VOM checks on the usual devices found in the home or shop. Here are some actual readings:

Radio                                                               5  ohms
Mixer                                                               7          ohms
Toaster                                                             11        ohms
Laundry iron                                                     14        ohms
10-inch fan                                                       22        ohms
3 hp drill-press motor                                       l½        ohms
7½-watt lamp                                                   400      ohms
60-watt lamp                                                    5          ohms
15-watt fluorescent heater ....                            5          ohms
Small soldering iron                                           700      ohms
Large soldering iron                                          85        ohms
Gun-type soldering iron                                     7          ohms

As with the Clicktester, a VOM in its resistance-measuring function must not be used on live circuits. The current that makes the meter operate comes from a self-contained flashlight battery.
 
The "Lightester"

To determine if exposed wires and terminals in house power circuits are alive or not, it is very useful to have a simple "Lightester." This is nothing more than a lamp socket with a short length of flexible wire, the ends of which are fitted with insulated test prods.

The socket should preferably be of the "keyless" type, without a built-in switch. If only a common socket is on hand, tape or otherwise fasten the switch in its "on" position. The lamp can be of any size whatsoever. Because the tester is carried about, and because glass bulbs are fragile, it is a good idea to protect the lamp with a simple wire guard that clamps around the neck of the socket.

The test prods can be merely six-inch lengths of 4-inch dowel. Solder the wires to headless nails about l½ inches long, and tape them securely to the ends of the sticks. Touching the nails to a suspected power line tells you instantly if it is alive or dead. The wooden handles provide more than adequate protection against shock danger.

With  a  switch  in  its   off   position,  the  ohmmeter  needle  should remain absolutely stationary when the  test  prods  are  applied  to  the  terminals.  A  high  resistance  indication  means  internal  leakage.

Above: With the Handitester set for ohms and connected to the prongs of a clock cord, the usual indication is several hundred ohms. No reading at all means that clock motor winding is open, or much less likely, that the power cord is open.

Below: The instrument shown in the photo is a VOM of a more advanced type (Precision Model 120), favored by electronic technicians and experimenters. Here it is being used to check the continuity and resistance of another clock motor.

The "Lightester" consists merely of lamp and socket fitted with two test prods. The latter are dowel sticks with nails taped to their ends. Lamp can be any size. Protective cage is insurance against accidental breakage of bulb. This tester is very useful for quick check   on   115-volt   lines.

With a 115-volt lamp in its socket, the Lightester is, of course, limited to the checking of regular 115-volt circuits. If you're tempted to try it on 208- or 230-volt lines, you'll get a bright flash for half a second, and then you throw away the bulb. It is rather difficult to buy 230-volt lamps (impossible, in fact, in most parts of the country), so for checking these higher voltages it is better to use the 300-volt AC scale of a VOM.

Tools for Electrical Work

Any electrical repairs you can't make with the ordinary hand tools found in the basement or garage shop you probably can't make at all. Look at the picture on page 41 of some basic tools and compare it with what you have in your own tool box: soldering iron or soldering gun; rosin-core wire solder; side-cutting, long-nose and diagonal-jaw pliers; assorted screwdrivers; knife for trimming insulation and cleaning wires; tape for covering joints in wire; hacksaw for cutting BX; and extension cord for bringing juice from a distant outlet when the circuit in a room is purposely opened to permit repairs.

Of obvious value are also such standard tools as wrenches, hammers, nut drivers, files, etc.
Tools for soldering take two different forms, the soldering "iron" and the soldering "gun."   In spite of its name, the "iron" uses a tip of copper. This is heated by a coil of resistance wire inside the body of the tool. Depending on its size, an iron takes from two to five minutes to reach operating temperature. It is ready for use when solder touched to the tip melts instantly.

The "gun," so called because of its resemblance to a pistol, is actually a step-down transformer. The primary winding consists of many turns of fine wire, and is connected to the house power line through a trigger switch. The secondary is a single loop of metal tubing or rod between about 3/8 and ½ inch in diameter, its exposed ends being terminated by a relatively thinner V-shaped loop of copper wire. Because of the large step-down ratio of the primary-to-secondary turns, the voltage across the loop is very low, in the order of two to three volts, and the current is very high, as much as 100 amperes. This heavy current causes the copper end loop to heat up. There is no danger of shock from the exposed secondary rods, because the voltage here is low and also because they are not connected directly to the house power line.

The big advantage of the soldering gun is that it comes up to operating temperature in about three seconds. It is especially handy for making just one or a few joints in a hurry. You can be all finished with most jobs in the time it would take a straight iron to warm up.

There are some soldering tools shaped like guns that are actually of the resistance-heating type.

Is juice reaching prongs of wall outlet? Insert prods   of   Lightester.   If  no  light,  line   is   dead.
 
Is  juice  reaching  terminals?   If  lamp  goes  on, one of contact springs in outlet itself is broken.

Lightester is especially valuable for determining whether power lines and fuses at cutout box are OK. Touch one prod to common ground (white) wire, other to house side of each fuse connection. Center fuse, lower row, leaves lamp dark, meaning it is blown out. Note method of holding prods by ends.
 
With test prod touched to terminal of lower right fuse, lamp lights up, showing that fuse and circuit are intact. Flickering of lamp often shows up loose or partially corroded fuses. Wire guard of Lightester provides convenient means of hanging the unit from any nearby edge that is available.

Basic  tools  needed for  home  electrical repairs  are  an  extension  cord,  straight soldering iron,  rosin core solder, knife, gun type soldering tool, a set of pliers, screwdrivers, plastic tape  and a hacksaw.
 
Which type of soldering tool to choose? The answer is easy: both. For some operations one is preferable to the other. For instance, suppose you are working on a change in a power line, and want to solder a joint in it. Obviously, you can't use a gun if you kill the line first to make the latter safe to handle. The trick is to heat up a regular resistance-type iron, kill the circuit, and make the joint while it's still hot. A medium-size iron will hold its heat for about 30 seconds, which is more than long enough for several joints. A gun-type iron goes dead almost instantly when it loses its AC power.

Rosin-core solder is universally used for electrical connections of all kinds. The rosin is known as "flux," and its purpose is to prevent the formation of a layer of corrosion on the surfaces to be soldered when the hot iron is applied. Rosin, a derivative of turpentine, has no corrosive after effects.

Diagonal pliers are intend only for snipping wire, not for holding, squeezing or bending. Their jaws form a sharp V, and they can therefore be used in close quarters for trimming short pieces of wire.

Side-cutters combine cutting edges and flat, fairly heavy jaws. The latter are suitable for a wide variety of holding, turning and forming jobs. In the six-inch size, this is probably the most frequently used tool in all electrical work.

Long-nose pliers usually do not include cutting edges. They are intended for making loops in ends of wires and for light holding purposes. Do not use them for twisting nuts on bolts or similar heavy work. Once the slender jaws become distorted through this misuse, the tool becomes useless.

No one ever has enough screwdrivers. You need small, medium and large ones, because electrical appliances contain screws of widely varying dimensions. Fortunately, screwdrivers are cheap and last practically forever. If the ends become worn, they can be restored in a minute with a file or a grinder.

You will also need two or three sizes of Phillips-head (cross-point) screwdrivers. Handle these carefully and be sure to use the right size for the screw. When they wear out or are damaged they must be discarded, as it is virtually impossible to reshape them.

An excellent knife for electrical work is the Army tool known as the TL-29. This consists of a sturdy knife blade and a locking screwdriver blade in common handle. ·

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