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How to Find Short circuit on the Motherboard

How to Find Short circuit on the Motherboard:​

It is necessary to understand that a single component in short can leave several other components also accusing short, just that they are in the same line.

So, to know if a motherboard is shorted more efficiently you will measure all the coils on the motherboard, as they are part of the main circuitry of the motherboard.

To do this, just do the following:

1- Place the multimeter on the 200 ohm scale.
2- Place the black tip on the plate ground and the red tip on the coil.

RESULT: If it gives 0 ohms then you have a short in the coil circuit that was measured.

Note 1: Some coils are part of circuits with low resistance, as is the case of the processor circuit and the chipset, for example. If you measure the coil of these circuits it will give you between 10 to 50 ohms, and that does not indicate a short, it is normal.
Note 2: On the other hand, the coils of the 3V and 5V circuit, of the memory circuit, have a higher resistance, this means that when measuring these circuits you will have something between 100 to 1000 ohms.
Switch mode power supply (SMPS) are designed so efficiently that whenever there is any short circuit occur in the motherboard, power supply would shut itself off and totally stop working. If you have no experience about troubleshooting switch mode power supply, you may think that the power supply have problem where in fact the motherboard is the real cause of no power problem.

Switch mode power supply have a current sense circuit and if there is short circuit in the output side (either in inductors output 3V and 5V section), the current drawn would be increase and this will lead the PWM IC to stop generating output to the power Mosfet and thus the power supply would shut down. All this happen in a split of seconds and you do not have the chance to know if there are output voltages at
the secondary side. Laptop motherboard Voltage requirements to life are ADP + 5V and 3V. the fast way to identifying ADP+ present in all measuring point needs is measuring on the SMPS IC input sources (VIN) and discrete Upper N channel Mosfet source , if this voltage
present no need to check ADP Mosfet and Bat Mosfet on VIN and BAT +VALAW section anymore . They should be already present.

Then measure the PL (inductors) for 3V and 5V for 3 & 5V system if they not present first step to check whether there is a feed back on 3V and 5V section lines by testing continuity to ground. If there is a feedback 3V and 5V system will not present although LDO and auxiliary power already present. Remove the Inductor (PL) with have a feedback , if pin 1 reply buzzer (diode continuity test)definite short coming from SMPS or discrete upper/lower N channel, n-channel leak test method by testing continuity (buzzer) pin 8 and pin 1 if there is continuity it‘s means Mosfet leaking and need to replace.

Check on schematic that lower upper string of n channel is connected to ground (lower) pins 1, 2, 3 if the upper n-channel leak it will also lower become leak and connected to ground to withstand voltage n-channel source into the path of 3V and 5V .do not lift lower n channel if this case happen, otherwise ADP+ will passing through to 5V & 3V section and damage all capacitors with maximum 6.3V allowed.
 

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