Use A DC Regulated Power Supply Detect Shorted Component In Main Board Or Mother Board Shorted Motherboard could be happen in very beginning VALW section .it mean short already happen on DC jack adapter , DC regulated power supply besides using it to power up electronic circuit it can also be use to troubleshoot and find out a shorted component in a motherboard? Assuming you have confirmed that the VCC supply lines shorted to ground through some faulty components, you can easily detect it with the use of a variable digital DC regulated power supply Using DC regulated power supply short circuit could identified by the PSU ampre meter after plug in jack adapter ,Current suddenly goes high and voltage drastically down or drop . Voltage usage 19V and current start at Zero before plug in and Look at the both monitoring current (Red) and Voltage (Green) after jack pug in to monitoring short circuit on VALW section. VALW section on Laptop motherboard have 3 block of section calls VIN or ADP+ ,VBAT or B+ and 3V_5V system (most common circuit design 3V_5V on VALW) but some of circuit design 3V_5V section on S_5 state or appear after switch . To check with multimeter use set to X 1 Ohm and measure between the supply pin and the main board ground and then reverse the probes. A good board should not show two similar reading and if you get two similar ohms reading then this means that the line had shorted to ground through some faulty components. Most potential cause of short on VALW section are capacitors ,They use as filter and 1 of pin embedded to the ground side . To find shorted component using PSU by pushing the voltage on that sort circuit and shorted component will goes hot and easy to find .To avoid any damage use lower voltage than ADP+ needs. Forexample if ADP+ 19V use 10V to inject and current not higher than 1.5Amp. The other potential cause of short are N chanel,when there is a leak on that mosfet ,lower n chanel became leak and connect negative line to positive line .Do not lift lower N chanel if upper N chanel leaking ADP+ sources will be get in to smps gate or enter to 3V or 5V section and could damage all component with is maximum voltage allowed only 6.3V Vccore Line also most potential N channel leak ,same as 3V_5V system Vccore got 4 N channel too.(left and right side N channel) or I call them Upper and Lower N chanel. Each Upper N channel on this line having source from ADP+ .As a switching transistor they only having out put as their Gate Value .If this and Upper channel leak than Lower N channel will leak also and connect negative line to positive line to stop ADP+ coming to Vccore line . Note : Short could be happen to VALW Source and VS_5,S_3,S0 VRAM,VCCP,VGFX. Quite often whenever electronic equipment don’t function or work, we would immediately suspect a faulty switch mode power supply. But do you know that defective or shorted components in the motherboard or main board could cause the power supply to stop working too? Switch mode power supply (SMPS) are designed so efficiently that whenever there is any short circuit occur in the main board , 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 main board 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 fet 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. Same way as inject VALW ADP+ section but the Voltage not allowed to inject more higher than Section inject Value . For example if short (feedback) Happen on inductor 3V section the maximum voltage injection not higher than 3V. If short happen on 5V inductor ,we not allowed to inject higher than 5V. Remember to not inject more than 1.2Amp or PCB could be burned. Why don’t I immediately turn the output voltage from the dc regulated power supply to 19V or 3V5 volts(depend of section short line identified If do this and if the faulty components turned hot too fast, this will lead the faulty component to open circuit. If the faulty component open circuit, the current draw will drop and the only clue that you have to identify the culprit has been destroyed! If this thing happens then you may not have a higher rate to repair the board. Of course you still can by replacing one by one the SMD spider IC’s but this will surely eat up lots of repair time. Now connect the alligator clip from the positive output supply in the main board and the negative output to the main board ground, plug in the dc regulated power supply. Slowly vary the knob clockwise and see the voltage increase. At the same time the current draw can be seen from the current digital meter readout. From experienced, if there is a short circuit in the main board, whenever the voltage is increase, the current will rise dramatically and if no short circuit there would be less current draw. if you observe that the current drawn also increase (rapidly) as proportion to the rise in voltage setting, you are now for sure that there is component shorted in the main board. What does this mean? It is a good news to us, because if the current drawn too much we can know the culprit by touching on the hottest components in the main board. Using your finger you can touch on any components that are very hot. Touch on the IC’s, diodes, transistors, capacitors and etc. Once you located that only one component that is extremely hot to touch then that was the culprit! That’s the real cause of shorted circuit and replace it an other one.
