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Help clarifying a basic question about fuses...

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arunb

Member
I have a IBM T23 laptop, the input voltage for the laptop is 16 V DC, I mistakenly powered it using a 21 V DC power source.
I did not notice this until after the system has booted up and run for 15 minutes.

I immediately switched OFF the laptop, and after a few minutes tried to start it using the correct voltage 16 VDC. (used the original charger for this). But the laptop would not start.

I checked up in the net and found that some of the fuses in the motherboard might have blown.

I have managed to locate a fuse. But I am unable to figure out how the fuse can be checked. I have attached a photograph of the fuse.

I checked the voltages across the fuse ends, ie: voltage between A and GND, voltage between B and GND. It is 16 V DC. Does this mean the fuse is OK ???.

Also why does the copper inside the fuse look 'eaten' away..does this mean the fuse is defective after all ???

Please help???

thanks
arunb
 

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q5101997

New Member
Check the resistance between A and B. It should be zero ohms.
 

arunb

Member
yes it is zero.

I can't understand what went wrong, perhaps there are other fuses...

Anyway thanks a lot
 

RCinFLA

Well-Known Member
Do you mean the laptop does not work or does not charge from AC adaptor?

Was your battery good before and able to run the laptop without AC adaptor?

I hate to say this but putting a higher DC supply may result in higher heat build up in the series pass transistor of the battery charger circuit or the series pass regulator (both within the laptop) that runs the laptop when battery is weak or depleted.

These devices may have got so hot they burned out. Fuse did not blow because current was not high, just the voltage.

Look for a rather large (like quarter of inch) surface mount transistor, possibly with some heat sinking around them. They are likely MOSFET's.
 
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arunb

Member
the battery was depleted for a very long time, so I rigged up an external sealed lead acid battery, this worked very well for a long time. But recently I made some changes to the charger for the external battery...

But why doesn't the laptop boot up???

thanks
 
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