How to identify Mobo fuses

Bill MacIntyre

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Apr 28, 2013
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I have a post in this forum regarding a derad Lenovo Z710 motherboard
http://www.tomshardware.com/answers/id-3024253/lenovo-ideapad-710-power-leds-rewiring-faulty-power-cable.html

I have not had any replies to that post.
It appears that the problem is in the power or startup circuit as there is 20v on some locations on the board but no sign of life and no LEDs light at all, no fan etc.

I suspect it may be simply a fuse.
The problem occurred when my cat pulled the power cord out while it was running.
Can anyone give me any tips on how I can locate or identify what surface mount components are fuses so I can try jumping them.
Also if anyone has any troubleshooting tips for that mobo that wold be great.
Or- tips on where to get a replacement at a decent price.
 
So your cat wrenched the power adapter jack out of the laptop.
And it takes 20v from the power brick to run the laptop.

It`s not a fuse, that`s not the problem, not that it has any fuses on a laptop motherboard anyway.

It`s because the input jack inside the laptop has a frayed or damaged wire on it that may of come loose or unsoldered.
Or the physical part that excepts the power jack is damaged internal to the laptop.

If any of the plus red wires, or the negatives in black are broken on the back side if the internal jack acceptor, molded housing internal to the laptop, it`s why you are not getting power across all of the motherboard Bill.

Check the internal jack housing in side the laptop that excepts the power jack from the power brick.
For any broken off red or black wire sets. They will probably be bound up with heat shrink around the point where the wires are soldered to the + and - points of the housing.

Wiggle, try powering on while pinching or holding, or wiggling.
If it turns out to be the case you can buy a new cable from Ebay for your model of laptop to fix it.

Click on the link bellow to see what I mean about snapped or frayed wires, you will notice two red + wires and three black negatives - Multiple power inputs to the laptop motherboard Bill, fail = snapped wire on the 37SA side. Dead power across a side of the laptop motherboard.

http://www.ebay.co.uk/itm/DC-POWER-JACK-HARNESS-PLUG-CABLE-FOR-LENOVO-IDEAPAD-Z710-Series-/111941518593?hash=item1a103c0501:g:8EIAAOSwMORW7bLi

 

Bill MacIntyre

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Apr 28, 2013
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Thanks for the tips guys but I am past that...
I have already done the following:
Cut the faulty plug from the adapter and hard-soldered it to the motherboard power connector.
See the link in my original post to another forum post that shows pictures and details of how I did this.
On the original connector there are 2 black negative wires, 2 red + wires and a blue wire which I thought was also + so I tied that (center pin on mobo) also to +.
I since (last night) realized that that center pin which goes to the center pin (blue wire) on the original rectangular Lenovo adapter plug is not actually tied to the other 2 + pins.
If you look real (real) close on the mobo you can see the center pin has a very fine non copper ring around the pin on the circuit board.
I read that the blue center pin wire has a resistor going to ground which the mobo uses to determine the power adapter power rating.
I tried connecting various resistor values from that pin to gnd and still no LEDs light up.
I also found a few troubleshooting guides that say that most laptop mobos use similar circuits for battery charging but still I am not sure how to troubleshoot this. I can trace 20 V part way thru that circuit.
I still assume that connecting power to the bare board with nothing connected except for the power switch board should give me at least one LED indicator lighting on the board.
I have attached a few more pics I took last night.
Lenovo1.jpg

Lenovo2.jpg

Lenovo3.jpg

Lenovo4.jpg

Lenovo5.jpg

Lenovo6.jpg