Are tone circuit testers sensitive enough to find a hidden junction box?

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ESSENTIAL FOR SERVICING DIGITAL PROJECTS



This is another invaluable piece of test equipment for digital work. It has been designed by us to cater for a particular application . . . servicing digital projects sent in for repair.
The first thing you have to do with an unknown project is test the trackwork. This consists of testing all the tracks for continuity and all the pins for absence of "shorts."
A Continuity Tester looks to be a fairly unimportant device and hardly seems worthwhile constructing, but after you have used it, you will realize how important it is.
A multimeter can be used but it takes much longer to do the same job.
Our Continuity Tester has been specially designed and has three very interesting features.
I'm sure you will add it to your set of test equipment . . .

Our CONTINUITY TESTER gives an audible indication of continuity between the probes so you can keep...
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Learn about the audible circuit probe tool and how to use it to troubleshoot everything from home wiring to electronic circuits.

The Circuit Probe

The Audible Circuit Probe is a handheld audio-oscillator with a sharp probe and an alligator clip for connections to test circuits. Its output tone varies with the component connected between the alligator clip and the probe. It is capable of testing resistors, AC and DC voltage, capacitors, diodes, and transistors.

Inside the tool, the alligator-clip connects to a film capacitor with a 250 V rating (J2), and the probe tip connects to the anode side of a diode (J1).

This is a single-swing blocking oscillator circuit, used to create narrow timing pulses.

Continuity Testing

In the short circuit condition, the probe outputs an approximately 800-Hz tone through a series of rapid pulses.

Tone produced by speaker during short circuit

Closeup view of speaker...

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As others have mentioned, you need to test continuity of every neutral line from the box to the end of the circuit, and then once you have ruled a bad line out, then you should start checking the outlets if they are all carrying the load of the one ahead of it.

To test continuity of the lines you do not need power, just a voltimeter tool so you can shut off the circuit. Starting at the first outlet, set your voltimeter to a low Resistance setting and test the neutral from the lead to the ground wire. You should get a near zero reading meaning No Resistance. Assuming your breaker box was installed correctly, Ground and Neutral should always have near zero resistance as the Neutral and Ground bars at the breaker box should be connected.

If you happen to get 1 or some noticeably higher number then that effectively means Infinite Resistance or that the Neutral and Ground are in no way continuous. That means that effectively the Neutral wire that you have just tested is...

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Uses Sound to Detect
Once connected to the circuit, VERIFIER passes an audible tone along the cable and through the connected circuit devices. This tone is heard through the supplied inductive amplifier probe when passed near the cable or individual device.

Constant and Distorted Tones
VERIFIER makes it easy to ‘hear’ a fault. A healthy device will produce a clear and constant tone whereas a troublesome device will be identified with a distorted, varying tone. Clear changes in tone will quickly tell you what’s working and what's not.

Walk-Test an Installation Quickly
With VERIFIER it makes it easy for an alarm installer to walk-test an installation and ‘listen’ for any faults. There’s no need to test individual devices before a fault is found.

Trace Hidden Cables & Pinpoint Cable Faults
Listen to the tone to find and follow hidden cables behind plasterboard, carpet, floorboards and above ceilings. Any cable resistance fault, short or break...

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If you are looking for a simple circuit for test continuity of wires and long conductors, this circuit is the one which you can try and might fulfill your requirement.

What is a Continuity Tester

A continuity tester is a device which is used for identifying the correct continuity of a particular conductor in question. Or in other words the device may be used for tracing faults or breaks in a particular conductor or a wire.

The device is actually a simple LED and a cell circuit, where the LED is made to switch by passing the cell voltage to the LED via the conductor in question.

If the conductor is not broken, the cell voltage circulates through it and reaches the LED to complete the circuit and in the course illuminates thre LED, providing the relevant information.

If the conductor is open internally, the cell voltage is unable to complete the circuit and the LED remains shut OFF, indicating the fault.

Using One LED and...

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SENSITIVE GEOMAGNETIC DETECTOR

Published:2013/5/7 21:14:00 Author:muriel | Keyword: SENSITIVE GEOMAGNETIC DETECTOR

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This is a rather sensitive circuit which will detect minute variations of a magnetic field, particularly the Earth magnetic field. The principle is based on an audio beat tone generated by two identical oscillators. These must be built in the same manner with the same type of components. In this way we minimize influence from temperature and voltage variations. The two oscillators, called probes, are housed in plastic boxes padded, on the inside, with copper wires terminated in one point only and running parallel to the ferrite rod. This rod, together with the coil was removed from an old Medium Wave radio and a small and powerful magnet was glued on one side. An extra magnet was placed on the outside of one of the boxes in order to set the initial or zero beat tone. This magnet is...

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"No-one gets an ironclad guarantee of success. Certainly, factors like opportunity, luck and timing are important. But the backbone of success is usually found in...

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Circuit diagram

Parts
R1 1K
R2 2K2
R3,R4 22K
R5 2K7
R6,R7 56K
R8 *See text
C1,C2 22nF
D1,D2 1N4148
Z1 8V2, 1/4 watt
T1 2N3905 (PNP)
T2,3,4,5 2N3904 (NPN)
9volt Alkaline battery
suitable loudspeaker
housing & probes

An on-off switch is unnecessary. D1 is used when the battery
is brand-new and giving over the nominal 9volt, T1, T2 and T3
acting as the switch for supplying power to the multivibrator.

Design Considerations:
Several simple circuits were tried -- a lamp, battery and probes still demanded the attention of the eyes; replacing the lamp with a buzzer was more successful but needed some three to four volts and gave no indication of a series semiconductor junction if the polarity was correct while the current flow was large enough to damage the more delicate devices within the circuit under test. An extension of...

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Silk-screened Panels - All Collins and Motorola R-390A receivers use front panels that have silk-screened nomenclature. This presents a problem if the panel is in rough condition. About the only solution is to look for a decent condition replacement panel. If originality isn't an issue, a silk-screened panel can be replaced with an engraved panel. Be aware though, that Collins and all of the other contractors used a short serial number tag with the exception of Motorola. The Motorola contracts used a 3" long tag with different locations for the mounting holes. If you're trying to maintain originality with a Motorola contract R-390A, then you're going to have to find another Motorola front panel. (Note: Early contract Collins R-390A receivers also use the long 3" data tag.)

Engraved Panels - Repainting an engraved front panel is very easy. Be sure to mask the back of the panel (if you're going to paint it) where the panel mounts to the Main Frame and also a...

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