Trouble finding the shorted parts.

[anthrax0987]

I was diagnosing a laptop with a shorted capacitor or mosfet.

I cannot figure it out. The only weapon that I have is a analog multimeter "Sanwa" type.

Laptop is complete black and no Indicator. Is there such a technique to check those capacitors, diode, MOSFET in a way that I can pinpoint the problem in a good amount of time.

Is there a tutorial out here or and URL that you can share? or anything that becomes my resource?

[inflex]

Re: Trouble finding the shorted parts.

If the meter has a diode-test mode, then use that. Place +ve probe to the ground and see what you get at the various points on the board. 0.4V or greater usually isn't a short. Essentially the lower the reading in diode-mode, the more "shorted" it is.

[piernov]

Re: Trouble finding the shorted parts.

Warning: low resistance/voltage drop on CPU VCore or GPU VCore is usually not a short, NB/SB/PCH can have low readings too. Remove CPU if you can. When you check in resistance mode, you can only conclude those lines are shorted if you get something lower than 0.5-0.3ohm. However, you may still have a shorted cap when the reading is higher. Shorted caps can give a few ohms resistance, you won't be able to see that on a low voltage/high power line.

[inflex]

Re: Trouble finding the shorted parts.

Warning: low resistance/voltage drop on CPU VCore or GPU VCore is usually not a short, NB/SB/PCH can have low readings too. ...

That's good advice

[anthrax0987]

Re: Trouble finding the shorted parts.

Warning: low resistance/voltage drop on CPU VCore or GPU VCore is usually not a short, NB/SB/PCH can have low readings too. Remove CPU if you can. When you check in resistance mode, you can only conclude those lines are shorted if you get something lower than 0.5-0.3ohm. However, you may still have a shorted cap when the reading is higher. Shorted caps can give a few ohms resistance, you won't be able to see that on a low voltage/high power line.

I've done this I removed the processor. but what if its like an i3. some motherboards processor cant be remove.

So it means that I need to take those capacitors one by one and test them. What I did is that I tried the continuity of my multi meter and the continuity is always equal to some capacitors.

[sancheti81]

Re: Trouble finding the shorted parts.

give supply 3v to 5v on dc socket and check if any cap is getting heated

[rievax_60]

Re: Trouble finding the shorted parts.

give supply 3v to 5v on dc socket and check if any cap is getting heated

What might look like a short to ground on the VBAT rail can sometimes be a shorted Buck regulator high side MOSFET. Any voltgae applied to the VBAT rail will be applied to what ever the regulator is powering, CPU, GPU.
Dont apply much more than 1 volt.
Most laptop designs have a protection that prevents the input protection MOSFETs from being turning on if there is a short on the VBAT rail, when voltage is applied to the DC socket.

[tablet3rs]

Re: Trouble finding the shorted parts.

kabayan,

you might want to start on inductors, set the analog meter to x1 check both sides of inductor, check all the inductor, usually L or LP labeled in laptop board,

might save you a lot of time in finding shorts,

have you check the charger, charging port and the fuse right to the charging port?

good luck

ps got here example of mobo where youll find inductor if you dont have any idea what inductor looks like,

and look for schematic of you mobo or boardview....
[IMG][/IMG]

[anthrax0987]

Re: Trouble finding the shorted parts.

kabayan,
ps got here example of mobo where youll find inductor if you dont have any idea what inductor looks like,

and look for schematic of you mobo or boardview....
[IMG][/IMG]

It's a coil bro right? The coil is shorted too. but some are not. and how can i supply a 5v power in my board, like what above you have said. he said that i must apply 3v or 5v then look for a heating part. are you working in SST Laptop?

[tablet3rs]

Re: Trouble finding the shorted parts.

you must remove 1 pin of the inductor (coil) and find out which side is shorted or both are side shorted...

schematic is a must to be able to pin point what component(s) is shorted,

[mehtabbukhari]

Re: Trouble finding the shorted parts.

Hi,

Please let us know your model no. or board id so that we can help you with the schematics.

[inflex]

Re: Trouble finding the shorted parts.

Hi,

Please let us know your model no. or board id so that we can help you with the schematics.

As a side note ( and I apologise for diverting the topic ), do you have access to the ASUS X550CC schem? I've tried many places, even tried laptopschematic, no luck. I can get the X550CV and other similars, but not the X550CC.

... and back to our regular channel ...

[mehtabbukhari]

Re: Trouble finding the shorted parts.

Sorry, I don't have X550CC schematics.