In electronic circuits, in addition to contact more electronic components (such as resistors, capacitors, inductors, diodes, transistors, integrated circuits, etc.) in addition to other commonly used electronic components, such as electro-acoustic devices, connectors and switches.
1 Electroacoustic devices
Electro-acoustic device refers to the electro-acoustic can be converted into audio electrical signals or audio electrical signals into acoustic devices. Common electro-acoustic devices are speakers, microphones, headphones and so on.
1.1 Speaker
General detection of high, medium and bass speakers intuitive discrimination: due to the effective frequency range of the test speaker is more troublesome, so more based on the size of its caliber and the softness of the paper cone to carry out intuitive judgment in order to roughly determine its frequency response. Generally speaking, the larger the caliber of the speaker, the softer the edge of the paper cone, the better the low-frequency characteristics, in contrast, the smaller the caliber of the speaker, the harder and lighter the paper cone, the better the treble characteristics.
Sound quality check: Use the multimeter R × 1 Ω gear to measure the impedance of the speaker. The pen touches the pin, you can hear the sound of the klaxon, the klaxon the louder the speaker, the more efficient its electrical - sound conversion, the klaxon the more crisp, clean speakers, the better its sound quality. If the multimeter pointer does not swing when touching, it means that the voice coil of the speaker or the voice coil lead line is broken; if only the pointer swings, but there is no clicking sound, it indicates that the voice coil lead line of the speaker has a short circuit.
1.2 Microphone
General test: dynamic microphone can use a multimeter to determine the good and bad (condenser microphone should not be measured with a multimeter). Measurement, the multimeter will be placed in the R × 10 Ω or R × 100 Ω gear, the two needles and microphone plug ends are connected, at this time, the multimeter should have a certain DC resistance indication, high impedance microphone is about 1 ~ 2 kΩ, low impedance microphone is about dozens of ohms. If the resistance is zero or infinity, it means that the microphone may have been short-circuited or disconnected internally.
1.3 Headphones
General testing: commonly used headphones are divided into two types: high impedance and low impedance. High impedance headphones are generally 800 ~ 2000 Ω, and low impedance headphones are generally about 8 Ω. If you find that the headset is silent, but the sound source is good, you can measure it with the help of a multimeter.
When checking the low impedance headphones, use the multimeter R × 1 Ω gear, the method can be referred to with the multimeter to identify good and bad speakers.
High impedance headphones to measure the multimeter, the multimeter will be dialed to R × 100 Ω gear, the general pointer pointer about 800 Ω or so, if the pointer points to the R = 0 or the pointer does not deflect, it shows that there is a malfunction, then the headset terminal may be short-circuited or circuit-breaking. Unscrew the headphone plug, if you find the wiring on the terminals are not wrong, which means that the headphone coil is faulty.
Stereo headphones are generally three-pronged plug, two core wire in one is the R channel, one is the L channel. Simply equal to the two headphones, so check the inspection can be checked separately.
2 general detection and selection of connectors and switches
Connectors and switches, the general point of its detection is reliable contacts, accurate conversion, generally with visual inspection and multimeter measurement can meet the requirements.
( 1) Visual inspection
For non-sealed switches and connectors, visual inspection can be carried out first, the main work in the inspection is to check whether the whole is intact, whether there is any damage, whether there is any damage, deformation, looseness, oxidation or loss of elasticity in the contact part, and the wave switch should also be checked to see whether it is accurately positioned, whether there is any misalignment, short-circuit and so on.
( 2) Measurement with a multimeter
Place the multimeter in the R × 1 Ω block and measure the DC resistance between the two contacts, which should be zero, or else the contacts are not in good contact. Place the multimeter at R × 1 kΩ or R × 10 kΩ, measure the resistance between the contacts after the contacts are disconnected, and between the contacts and the “ground”, and this value should tend to infinity, otherwise the switch and connector insulation is not good.