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How to test a fuse...


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Pnutbutters Pnutbutters is offline
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Experience: Intermediate
17-May-2012, 03:03 PM #1
How to test a fuse...
My motherboard will power on for 3 seconds and then blink orange lights... I took it apart and replaced a few capacitors but that did not work.

It is not the fan.. and I removed every component I could. It is basically just the motherboard and the two main chips..

The motherboard belongs to a toshiba x205-sli1

I think it might be the fuses... but does anyone know how to test them??

And if they test bad how do you replace them?
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Dexters Dexters is offline
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25-May-2012, 10:19 AM #2
Motherboard Fuses
Motherboard fuses can be replaced just as easily as a capacitor. The recommended way to test if the fuse is good or not, is to remove all solder from the board fuse location pins and then test resistance with the fuse out of the board's circuit . Just use a multimeter (ohmeter) and test for resistance across each side of the fuse. Most meter's have a little button that looks like a single volume button, press this and it should beep when you have no resistance, if you have no resistance on the fuse, it means your fuse is good (i.e. you get a beep). If you don't hear a beep and your resistance is like 10, 20, 100, 200+ ohms then you have a blown fuse. You will probably have to buy the replacement fuse online, but Radio Shack might have it.

The problem with troubleshooting a motherboard is that it can be quite complex. There is typically no good method to follow unless you are extremely electronic capable.

I would start by following the power through each supply/segment. I have seen problems like this in the past be related to power supply failures, not motherboards. Motherboards do fail, yes, but a more common issue would be a power issue in the board.

What I would do is test the power board power supplies, the problem is, the only way to do this is with the laptop power on. That is NOT RECOMMENDED, it is not really dangerous, since it's only 19VDC @ 60/70 Watts, but it is a good way to mess up your computer if you're not aware of what you're looking for. I would test the voltage coming in, then on your laptop power board, it then converts that 19VDC to multiple voltages used by your hardware. Your video card probably is like 8.5 V and this power is stepped down from your DC Converter from the wall.

I hate to say it, but it's usually a bad day when the motherboard goes bad on a laptop, because it can be extremely difficult to fix. If you could show some pictures, and maybe say what led you to replace capacitors it may be helpful. Was there liquid coming out of the capacitor? (Usually the top X is busting outwards if this happens? They are made to bust, but you can usually see it).

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Dexters Dexters is offline
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25-May-2012, 10:21 AM #3
Fuse Testing
I forgot to say also, you can test the fuses while they are still in the motherboard, just make sure you have almost NO resistance. You could see little resistance, but your fuse still be blown, because you could be reading through leakage through your PowerSupplies. That is unlikely, and you will be able to notice it. If you find a bad fuse, use a solder gun, take it out and then test it once's it's out. If it's truly bad, then you are lucky, you can just buy a new fuse and enjoy your computer again.
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