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In this lesson we will talk about the troubleshooting process of the PWM circuit in the graphics card

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Most of the power supply in the graphics card is generated by the PWM circuit.

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When the PWM circuit is abnormal, the fault phenomenon of the graphics card is generally a lack of power supply.

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Graphics card will not display after power on

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To repair a PWM circuit, the first step is to check for cosmetic faults

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In the second step, we need to find the first abnormal power supply according to the timing

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Through our previous analysis of timing,

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we can know that the power supply of the graphics card is a series of down

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If we want to repair the power supply, we must find the first abnormal power supply.

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If there are measurement points on the graphics card, it will be much easier to find

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After finding the first abnormal power supply,

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we need to measure the ground value of this power supply to confirm whether it is short circuited

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If the power supply is short-circuited, the short-circuit fault should be repaired first.

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After confirming that the power supply is not short-circuited, you can continue to repair

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After confirming that there is no short circuit,

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we will measure whether the power supply and opening of the power supply chip are normal

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If the power supply and opening are not normal, then we must first fix its power supply and opening

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Power supply and turn on are the most basic external conditions required for power supply chips

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When a power supply chip satisfies the power supply and is turned on, it can basically work

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If the chip is powered on and has an open signal, but still does not output power,

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we consider replacing a power supply chip first.

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If the replacement of the power supply chip is still not good,

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then there is a problem with the circuit around the power supply chip

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We first need to measure whether the VCC 5V linearity of the power supply chip is normal

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If there is a problem with the 5V linearity, the power supply chip will not work

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Confirm that there is no problem with the 5V linearity,

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and we measure whether the circuit related to FB is normal

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If there is a problem with the FB circuit, then the output power supply will not be normal

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Next, we measure whether there is a problem with the REF related circuit

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Because the REF circuit in the power supply chip is generally used to control the FB voltage

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If there is a problem with the REF circuit, then the output voltage will also be a problem

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If there is no problem with these measurements, then this fault will be more difficult to repair.

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We can consider replacing all the components around the PWM circuit for him

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Of course, the specific analysis of the specific chip is just a general maintenance process here.