Odd laptop behaviour - Any thoughts?

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Negan
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Tim
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Bit of an odd one this.
We have a Toshiba L855-15U laptop.
It is currently *sometimes* refusing to power on regardless of whether it is plugged into it's power supply or on battery.

I've tried the 'remove battery, hold down power button for 10 seconds" reset trick, to no avail, it appears dead...

However, plug it into a different Toshiba power supply, the charging light comes on and you can power it on. It's reporting as fully charged and if you plug it back into it's own power supply, it continues to charge.

I've checked the alternative supply, it's 19V 4.74A which as far as I can see is the correct supply for the L855-15U.

Any thoughts?
My initial thought is it is something to do with the power supply, I've suggested powering it on without the PSU plugged in for the next few days to see if the behaviour is repeated (so far it's always been connected to the PSU on the first attempt to boot). But I don't understand why swapping it to a different power supply would make it work.
I'm quite happy to buy another power supply if that'll fix the problem (but don't want to waste money if it's unlikely to).
 
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The two alternative ones are rated at 19V, 4.74A.
As far as I can tell the original is rated the same (but the sticker has been removed - teenagers huh?).

I've not run a voltmeter across the supplys.

(Presumably I simply attach the probes to the two terminals - I'm not going to short anything doing that am I?)
 
Just checked, measuring current needs to be done in series (I thought so, but it's a hell of a long time since I did my physics exams).
So it's going to be a bit difficult to measure the amps.
 
Just buy a new power supply.

I have had a number in the past for other electrical items fail and give false positives.

The inquisitive might want to know why, but finding out is usually time consuming and more hassle and expense than using a new one.
 
I think you're both probably right, that it's teh power supply and that I may as well buy a replacement rather than fault find.
However, I've asked her to start the laptop with no power supplies plugged in for the next few days just to check that the fault goes away.
 
Update this morning.
After being left unplugged overnight, the laptop won't start on Battery alone.
Battery out + reset - Nope.
Refused to start on various different power supplies too.
Reseat memory + attempt restart (on battery) - Nope.
Replace cover and one last attempt to start attached to a PSU and the charging light comes on followed by booting.

So... Probably not the charger then, probably something loose (dry joint?) inside.

Ah well, it's 2 yrs old and has been abused in the way that only a childs laptop can be abused. Will try to keep it running for another month and replace with a Windows 10 laptop.
 
Hi Tim
I have seen a few laptops with the socket for the PSU damaged, the board that socket sits on, try wiggling the lead/plug at the laptop end to check for movement and when powering up, hope this helps.
Pete
 
On those models I believe the charging socket is on a wiring loom and is easy enough to replace once you have got the laptop open. Normally pick them up for about £3-£5 on ebay. Sounds like the power isn't getting to the charging circuit.
 
That's useful to know.
I've agreed to get her a new laptop once Windows 10 machines are generally available, but the machine is new enough for me to attempt a fix on (or send it away) and then use as a spare / testbed.
 
Might be an idea to check if the power is getting through to the battery connections, plug the laptop in and connect your multimeter to the battery connection points and see if you get any readings.
 
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