The power selector switch,battery or mains, may be at fault and because it is on the mobo,could be difficult to repair or replace.I'm not familiar with your laptop,if you can find a decent circuit diagram,it might be possible to test the switch.
Sorry,can't help further.
What do you mean by mains of the laptop?
By the way, there's actually one problem I still encounter when using AC. For example, last night I left it with AC plugged in, the laptop was turned off. The battery is removed, has been removed since this weird problem happened, just to remind you that.
OK, so, this morning I turn it on, the keyboard and LED of the ON button lights up, but the screen remains turned off, and it stays like that forever. I press down the ON button for a few seconds, it turns off. Turn it off again, same situation, screen turned off, backlit keyboard and LED's turn on, stays like that. The screen is not the problem, it's like it can't load anything, not even, the bios?
I try several times and suddenly, the screen lights up along the keyboard and LED's, the Lenovo logo appears, loads Windows 10, works fine.
This happened to me with the AC unplugged overnight. My CPU seems to work perfectly fine, so my SSD (Samsung EVO 850), GPU, RAM... it really looks like something power related is failing. I don't know if it has anything to do with it, but the time it turned on with the screen on, I pressed the ON button PLUS the SHIFT key. Not sure what that does. I know if you turn off a PC with the SHIFT pressed down, you force Windows 10 to fully shut down, instead of hybrid shutting down. But when turning on, I don't know. Safe Mode?
Nope, since the laptop booted Windows normally, showing the desktop and not a "safe mode" activated desktop.
Last edited by rambomhtri; 16 Jan 2020 at 09:59.
Mains power supply.There is part of the circuit which senses and controls which supplies the power,Mains or Battery.If you can test the PSU,this may determine if it is at fault.
Don't understand the last sentence---laptop went to normal desktop---
If by PSU you mean the external notebook charger, it works, I already said that I tested it in another laptop and it worked just fine. Oh, I forgot to mention a weird thing, talking about this. When I connect ANY charger during the "I'm at Limbo" time, right after plugging in the battery and removing it, which lasts like 5 minutes, that charger I connected gets "poisoned"?
I checked the volts and it normally has 20V or so. The "poisoned" charger reads 4V or if I remember correctly, even less. During that time, no matter where I connect that charger, it won't work.
Let me tell the whole story. I have charger A with the laptop A (lenovoY510p), and I have charger B with the laptop B. The B product works perfectly fine, it's an ASUS product and works just like any other working laptop.
OK, the process is this:
I plug in the battery A in the laptop A, no charger A plugged in. Turn it on, seems completely dead, no LED's.
I read the charger A and has 20V or so. Plug charger A in laptop B to check if it works, and of course it works.
Plug charger A in laptop A. Turn it on, completely dead.
I remove battery A from laptop A, turn it on again, completely dead.
I remove charger A from laptop A, proceed to plug charger A in laptop B. Laptop B doesn't get charged.
I unplug charger A from laptop B, read the charger A and has really low voltage, 4V or mV, I don't remember actually.
Wait a few minutes.
Plug in charger A in laptop A, battery A remains unplugged. Turn it on, nothing, dead.
Wait a few more minutes, try to turn it on several times, until suddenly, it turns on.
I turn it off, and then on, several times, works fine every single time.
The exact same thing happens if instead charger A I try charger B.
Whenever I plug in battery A in laptop A, it goes Limbo again.
Your Lenovo has a circuit fault,so has your charger A.The voltage should not fluctuate under test.
That would explain everything, but as I said, I tried charger B and the exact same thing happens. Charger B comes from laptop B and works like a charm, but I used it in laptop A to check if charger A was the problem. No it wasn't since another perfectly fine charger B behaves like charger A, and also charger A behaves like a normal, working charger with other laptops.
The figures you gave for the charger were 20v for one reading,then 4.5v for another.For any computer,the power supply MUST be constant.
The closest analogy I can give is a car battery.When disconnected should read a nominal 12v,an old lead acid is 13.2v,When under load then the voltage drops,but not to the extent you quoted for your laptop.
If the charger/battery will not work in a different machine,they are faulty.
If the do,then the mobo is faulty.
Can't help any further than this,long distance diagnosis of electrical faults is unwise and unsafe.
There should not be any erratic performance.
I know it's been some time but the laptop has been turned on for months until today, working fine. Today I had to turn it off to move it, and when trying to turn it on, this problem happened again. But, now, no matter how many times I try, the laptop will just turn on the keyboard light, the LED of the ON button and that's it, black screen, not even loading BIOS. I've removed the SSD and the RAM and behaves the same, so that means it's stuck BEFORE it loads the BIOS. The battery, someone asked, is fine, marking 3V. Now I'm gonna remove the solder to free the battery and force a clear CMOS. I hope that helps. Looks like it's a MoBo issue, but only during the power on phase, because as I've said, the laptop has been turned on for months and it didn't have any problem. I knew that the day I turned it off, it would be problematic, and I'm sadly right. I'll keep you updated. Any ideas are welcome.
Try removing the hard drive. I have seen a dead HDD prevent the bios from running.
I've removed the SSD, which is the main and only storage device. Still same behavior. After the physical battery BIOS removal, nothing changed, same behavior. Really, how can a laptop behave like this?
I've fixed and worked on thousands of laptops and I've never ever seen anything like this. It's like black magic. A few months ago after a few tries it would finally load the BIOS and go on, but now I've tried like 50 times, almost 2 hours trying, still stuck. Bummer...
- - - Updated - - -
It's ALIVE!!!
After like 24 hours trying, turning it on and watching how it gets stuck with the black screen, not reaching even BIOS, 5 minutes ago suddenly showed the BIOS post and initialized correctly. I'm not turning it off ever again, hahaha. Let's see how much I last with this freaking MoBo. I hate it so much right now, but I'm so excited and happy it turned on. I don't want to spend $90 in a MoBo because this laptop is way too old to spend so much, but I neither don't want to spend like $1200 in a desktop PC I'd be satisfied with. I'm on this thin line right now of too lazy to spend like $1200 in a proper modern PC (yeah, I either spend whatever it takes to make a good modern PC, or I spend nothing), and I'm aware this laptop is dying so $90 is kind of a waste.
By the way, I'm quite sure it's the MoBo what's wrong, the PSU works great in other laptops, and I'm starting to think the battery doesn't work because the MoBo. What's a mystery to me is why it turned on... I was about to give up, I've pressed down the ON button like 200 times since yesterday easily.
Edit again: the other day accidentally turned it off. It took 3 days of trying to turn it on again. For anyone that faces this issue, you just have to keep trying, whenever you remember to press the button, press it and leave it like that. Suddenly, one time, it will turn on correctly, at then try not to turn it off again.
Last edited by rambomhtri; 04 Mar 2020 at 16:18.
Quote