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How to quickly find GND in PCB?

When repairing the circuit board, sometimes it is necessary to measure the potential of a certain point on the board to determine what is wrong, and the selection of the reference point is generally to select the negative pole of the power supply, that is, the GND ground wire. Related article recommendation: GND in the circuit, what is its essence? The following figure shows several GND symbols.

When repairing the circuit board, sometimes it is necessary to measure the potential of a certain point on the board to determine what is wrong, and the selection of the reference point is generally to select the negative pole of the power supply, that is, the GND ground wire. Related article recommendation: GND in the circuit, what is its essence? The following figure shows several GND symbols.

How to quickly find the ground wire in the board has become a must-have knowledge. Below I have summarized several methods for your reference.

1. Find GND through electrolytic capacitors

The picture above is an induction cooker motherboard. We need to find the ground wire. First, we need to find the largest electrolytic capacitor on the board.

In general, relatively large electrolytic capacitors are used as a component of power supply filtering, and its negative pole is GND.

The largest electrolytic capacitor you see in the above picture is a power filter capacitor, which is rectified from the rectifier bridge and outputs about 300 volts of pulsating DC power, and then filtered by this capacitor to output a relatively smooth DC power. Its negative pole is the negative pole of the DC power supply, which is the GND ground wire we are looking for.

2. Confirm GND by looking at a large piece of copper foil

The picture above is a two-layer board. The points marked with red circles in the picture are the ground wires. It can be seen that it is connected to a large piece of copper foil. This is because the ground wire has a shielding effect, which can effectively reduce the interference caused by the ground wire loop, so the ground wire copper foil in the circuit board generally appears in sheets.

3. Confirm GND by looking at the logo on the connection plug

As shown in the figure above, there are generally various signal marks on the connectors of the board. We can confirm the ground wire by checking this mark. For example, the GND in the red coil in the above picture is the ground wire.

4. Find by integrated chip

There are usually various integrated circuits in the circuit board. If these integrated circuits need to have a power supply to work normally, you can confirm the GND by checking the pins of the chip.

As shown in the figure above, this is an 8-pin LM358 comparator. By looking up its information, you can see the function of each pin. As long as you know that the fourth pin is GND, you can find the ground wire on the board.

When repairing the circuit board, sometimes it is necessary to measure the potential of a certain point on the board to determine what is wrong, and the selection of the reference point is generally to select the negative pole of the power supply, that is, the GND ground wire. Related article recommendation: GND in the circuit, what is its essence? The following figure shows several GND symbols.

How to quickly find the ground wire in the board has become a must-have knowledge. Below I have summarized several methods for your reference.

1. Find GND through electrolytic capacitors

The picture above is an induction cooker motherboard. We need to find the ground wire. First, we need to find the largest electrolytic capacitor on the board.

In general, relatively large electrolytic capacitors are used as a component of power supply filtering, and its negative pole is GND.

The largest electrolytic capacitor you see in the above picture is a power filter capacitor, which is rectified from the rectifier bridge and outputs about 300 volts of pulsating DC power, and then filtered by this capacitor to output a relatively smooth DC power. Its negative pole is the negative pole of the DC power supply, which is the GND ground wire we are looking for.

2. Confirm GND by looking at a large piece of copper foil

The picture above is a two-layer board. The points marked with red circles in the picture are the ground wires. It can be seen that it is connected to a large piece of copper foil. This is because the ground wire has a shielding effect, which can effectively reduce the interference caused by the ground wire loop, so the ground wire copper foil in the circuit board generally appears in sheets.

3. Confirm GND by looking at the logo on the connection plug

As shown in the figure above, there are generally various signal marks on the connectors of the board. We can confirm the ground wire by checking this mark. For example, the GND in the red coil in the above picture is the ground wire.

4. Find by integrated chip

There are usually various integrated circuits in the circuit board. If these integrated circuits need to have a power supply to work normally, you can confirm the GND by checking the pins of the chip.

As shown in the figure above, this is an 8-pin LM358 comparator. By looking up its information, you can see the function of each pin. As long as you know that the fourth pin is GND, you can find the ground wire on the board.


"When repairing the circuit board, sometimes it is necessary to measur…