Basic electronic components for motherboard maintenance part 2

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Precept digital elements for upkeep half 2:

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We’ll resume on this article the essential digital elements wanted within the strategy of repairing the laptop computer motherboard, we’ll see on this article two elements: the fuse and the diode, we’ll focus on their features and their failures and how one can take a look at them.

The fuse:

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The fuse is a security part, it protects the circuit from overcurrent, it is product of a fabric that melts when an excessive amount of present flows by means of it thereby making an open circuit and stopping the present from flowing to the circuit and damages different elements.

Circuit image:

The image under is used to signify a fuse in a schematic:
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The letter F is used to signify a fuse.

The fuse failure:

The fuse has just one failure: shorted or minimize, it acts like an open circuit and stopping the present from flowing.

Tips on how to take a look at a fuse?

You possibly can take a look at the fuse utilizing the multimeter set as ohmmeter or the best manner set in continuity take a look at mode.

1- Testing with continuity take a look at mode:

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Set the multimeter to continuity take a look at mode then put every probe in a single terminal of the fuse, it would not matter the place, it you may hear a beep which means the fuse is okay, in case you do not hear a beep the fuse is shorted or minimize.

2- Testing with resistance mode:

You should utilize the resistance mode to check a fuse in case your multimeter would not have a continuity take a look at mode.
Set the multimeter to resistance mode, and select the bottom vary.
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– Join the probes to the fuse and press gently.  
– If the fuse is okay it is best to learn a really low resistance, and in case you learn 1 or OL it means the fuse is shorted or minimize.

Diode :

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A diode is a two terminal digital part used management the present circulation by blocking it in a single path (the reverse path) and permit it within the different one (known as the diode’s ahead path).

Circuit Image :

A diode has two terminals which might be polarized, the constructive terminal known as the anode and the adverse one known as the cathode, present can solely circulation from the anode to the cathode (from + to -), the circuit image of a diode is:
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And the letter used for diodes in circuits is D.

Traits of a diode:

There are some factors to think about when working with a diode:
– The diode doesn’t let the present circulation within the ahead path till the voltage reaches 0.three V for germanium diodes and 0.7 V for silicon diodes, this voltage known as the Ahead bias Voltage and it’s consumed by the diode, that means the voltage will drop by the Ahead bias voltage, instance: if the voltage from a battery is 3V, it is going to be 2.7V after a germanium diode and a pair of.3V after silicon diode.
– The diode blocks the present till a sure voltage known as The breakdown Voltage, after that the present will circulation within the reverse path.

Gentle-Emitting Diodes (LED) :

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A LED is a particular diode that emits mild when conducting present, it has the identical traits like the conventional diode, it permits the present to circulation in a single path and blocks it within the different one, it has a ahead bias voltage which is larger than the ahead bias voltage of regular diode (from 1.2V to 3V relying on the sunshine shade that emits).

Diodes Failure:

Diodes have two kinds of failures: short-circuited or open-circuited (minimize).
When the diode is short-circuited it acts like a wire permitting the present to circulation in each instructions, and when it’s open-circuited or minimize it acts like and open circuit and never permitting the present to circulation in each instructions.

Tips on how to take a look at diodes:

You possibly can take a look at a diode utilizing a multimeter and set it to diode take a look at mode, on this mode the multimeter will apply a small voltage throughout the diode terminal after which take a look at the voltage drop (the voltage consumed by the diode).
Notice: generally it’s essential to take away the diode from the circuit to check it.
Join the multimeter probes throughout the diode and notice the studying.
Reverse the take a look at probes and notice the studying.
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Readings evaluation:

– diode ought to examine 0.7V for silicon diodes and 0.3V for germanium diodes when it’s forward-biased (permitting the present to circulation), and OL or 1 when it’s reverse-biased (not permitting the present to circulation or performing like an open change).
– If the diode is short-circuited to shorted it’s going to examine 0.7V for silicon diodes and 0.3V for germanium diodes in each instructions.
– If the diode is open-circuited or minimize it’s going to learn OL or 1 in each instructions.

Resistance mode:

You may as well use a multimeter that doesn’t have diode take a look at mode to check a diode by setting the choice knob to resistance mode:
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Put the purple probe onto the anode (constructive terminal of the diode) and the black probe on the cathode (adverse terminal of the diode) and notice the studying.
This manner the diode is forward-biased and it ought to learn from 1000 Ohm to 10 M Ohm if the diode is nice, and it reads a really low resistance whether it is shorted and 1 or OL whether it is minimize.
Reverse the probes now in order that the black probe onto the anode (constructive terminal of the diode) and the purple probe on the cathode (adverse terminal of the diode) and notice the studying.
This manner the diode is reverse-biased and will learn 1 or OL, whether it is shorted it reads a really low resistance and the 1 or OL in each instructions it’s minimize.

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