Lenovo ideapad 520 power on issue

[lordmmx]

Hello once again guys,

I am thinking about buying Lenovo ideapad 520 for fix, that have power on issue. I don't have that laptop in my hands now so I can't really tell what model of mainboard is in it. Anyway...

Thing is it powers on only after cmos and main batteries are disconnected for a while. If one of batteries is left connected, it will not turn on at all or turn on but stay on black screen.

I have seen this issue before on different models of ideapad and newer found a solution to it so I decided to ask here, maybe someone knows what's wrong.

Any ideas? Thanks

[lordmmx]

Re: Lenovo ideapad 520 power on issue

ok, so i decided to buy it anyway, still can use it for parts.

motherboard is nm-b452

and here are videos of what it is doing and I also did some measurements of voltages

also I just found out that once it get's geforce drivers installed it shuts down immediately

https://www.youtube.com/watch?v=uqvXLSAhMag
https://www.youtube.com/watch?v=6NMDSBNpgqw
https://www.youtube.com/watch?v=XoqalO3EsPE

[mon2]

Re: Lenovo ideapad 520 power on issue

Check the voltage of your battery. What is the reading without the adapter ?

If the battery reading is enough to power the logic board, remove the adapter and connect the battery. Check the operation of PQ314 mosfet.

Voltage reading on PQ314 - pins 1-2-3 ?

Voltage reading on PQ314 pin 5 ?

[lordmmx]

Re: Lenovo ideapad 520 power on issue

another thing i found out is that if i hold power button it turns on from battery, shows lenovo logo, keyboard lights up and then it turns off. if i hold it a bit longer it actually starts to boot but once i release the key it shuts down in next 3 seconds

also can you post the schematics please?? is there a boardview too ?

[lordmmx]

Re: Lenovo ideapad 520 power on issue

voltages are

without battery:
pin 1 - 0.84v
pin 2 - 0.83v
pin 3 - 0.84v

with battery:
pin 1 - 8.59v
pin 2 - 8.59v
pin 3 - 8.59v

pin 5 - 20.3v

[lordmmx]

Re: Lenovo ideapad 520 power on issue

and without AC only on battery voltages are:

pin 1-3 - 8.29v cca [0.02 change over pins]

pin 5 - 8.28vv

altought
pin 4 says 14.2v

[mon2]

Re: Lenovo ideapad 520 power on issue

Does the unit boot normally with the adapter only (no battery) ?

Do you have an attached SSD / hard driver ?

If yes, remove it and try to just confirm that the logic board is stable to show the BIOS, etc. screen.

You could even remove the memory stick -> power on and see if the unit beeps due to the missing ram stick.

Check the attached boardview file and post back if you cannot read this format. Will upload another reader to allow for this.

[lordmmx]

Re: Lenovo ideapad 520 power on issue

if battery and cmos battery is disconnected, it turns on from adapter and runs fine , boots into windows and install drivers - dies once it installs nvidia driver, if i disable it in bios before letting it to boot, it will work normally.

also fan is running at max speed for some reason.

[mon2]

Re: Lenovo ideapad 520 power on issue

Study the CMOS RTC battery dual diode and resistor network @ PR102 & PR103.

Are they ok ?

[lordmmx]

Re: Lenovo ideapad 520 power on issue

diode seems ok

multimeter set to 20k ohm ,

pr102 says 1.5
pr103 says 5.5

[mon2]

Re: Lenovo ideapad 520 power on issue

PR103 does not appear to be the schematic value of 45k3.

Perhaps you can remove PR103 from the circuit and measure again? Consider to source a replacement for PR103 if does not match.

Immediately do not see this to be a factor on the raised issue but worthwhile correcting this resistor to factory value.

[lordmmx]

Re: Lenovo ideapad 520 power on issue

pr103 removed, says 10.3 now

[mon2]

Re: Lenovo ideapad 520 power on issue

According to the schematic, PR103 is not the correct value.

It should be 45k3 = 45.3k = 45,300 ohms.

From your meter reading, PR103 = 10.3k = 10,300 ohms ?

I would replace this part with the correct resistor but do not see this as a fault that can cause the observed issue.

[lordmmx]

Re: Lenovo ideapad 520 power on issue

yes, 10.3kOhm , anyway, i'll look up one on my spare boards.

I don't think it is the issue that's causing the board not to work when battery or cmos battery is connected in.

Also I have observed this:

https://www.youtube.com/watch?v=cySZEq9O0B4

it works as long as i hold the power button.

[lordmmx]

Re: Lenovo ideapad 520 power on issue

Guys, any ideas what could this be? thanks a lot

[lordmmx]

Re: Lenovo ideapad 520 power on issue

SOLUTION FOUND: REPLACE KBC - fits from ideapad 330 without issue or get programmed one from ebay/aliexpress. laptop works flawlessly now

[lordmmx]

Re: Lenovo ideapad 520 power on issue

a year later, i still have laptop, but it developed another symptom. Fan runs at full speed all the time, once cpu get's over 50°C and no matter how hot or cold it runs, fan goes full blast all the time. It's fine while gaming but it's annoying when watching movies or working.

Board is almost identical to one in ideapad 330 , so if anyone had any idea what can be an issue, please let me know.

[lordmmx]

Re: Lenovo ideapad 520 power on issue

issue with fan solved by.... replacing the fan...