Cmos reset works for 7-10 days only

[mcplslg123]

Hi friends,

I've faced this problem in
1. DEll inspiron 3537-LA-9981P
2. HP 15-R series LA-A992P i3 MB
3.Lenovo AIO PC C20-30 LA-B691P.

Problem: Laptop switches but no display. No VS voltage present, Fan doesnt Spins. Doing CMos reset solves the problem and there is display. Cmos put back and packed. Works for 7-10 days and again same issue.

I've checked each and evry component in RTC Circuit and did'nt find anything wrong in all three cases.

It is not possible to do cmos reset every week to continue working-So my question is why this is happening.

In fact i've observed this problem In La-A992 on multiple occasions with different mb each time.

I seek your valuable suggestions and advice.

[mcplslg123]

Re: Cmos reset works for 7-10 days only

All three cases have CPU+PCH in one die and are haswell/broadweel platform.

[SMDFlea]

Re: Cmos reset works for 7-10 days only

The first thing i thought of when i read 7-10 days was connected standby

[tomodachi]

Re: Cmos reset works for 7-10 days only

1. DEll inspiron 3537-LA-9981P has ENE KB9012 chip
2. HP 15-R series LA-A992P i3 MB has ENE KB9012 chip
3.Lenovo AIO PC C20-30 LA-B691P. I believe also has ENE KB9012 chip

Always coming across to strange issues with KB9012 series programmable chips. I suggest you to examine datatasheet of this chip.

[mcplslg123]

Re: Cmos reset works for 7-10 days only

1. DEll inspiron 3537-LA-9981P has ENE KB9012 chip
2. HP 15-R series LA-A992P i3 MB has ENE KB9012 chip
3.Lenovo AIO PC C20-30 LA-B691P. I believe also has ENE KB9012 chip

Always coming across to strange issues with KB9012 series programmable chips. I suggest you to examine datatasheet of this chip.

Yes you are right. All three cases have 9012 as kbc. Can you elaborate a bit more on what to look for in datasheet.

[tomodachi]

Re: Cmos reset works for 7-10 days only

Yes you are right. All three cases have 9012 as kbc. Can you elaborate a bit more on what to look for in datasheet.

First thing I would do is backup KBC dump first and replace it with a new KBC, then flash the dump to new one.
Not sure where to start looking in with this issue, but if you able to find a good working KB9012 containing board you can make an ohms and voltages comparison maybe.

[mcplslg123]

Re: Cmos reset works for 7-10 days only

Thanks tomodachi for your replies. I do have new kb9012. Will try soldering new kbc and program it. Lets see as it will work for 7-10 days anyways. So update only after 10 days.

Any other advice from senior members here??

[SMDFlea]

Re: Cmos reset works for 7-10 days only

Were all 3 cases running ULV CPU`s

[mcplslg123]

Re: Cmos reset works for 7-10 days only

Were all 3 cases running ULV CPU`s

Though i'm not 100% sure but i do beleive these newer onboard cpu+pch are all ultra low voltage cpu to extend battery life. In case of lenovo it is quadcore cpu, rest 2 mb dell has i5 cpu and hp has i3 cpu.

[mcplslg123]

Re: Cmos reset works for 7-10 days only

I'm inclined to do what tomodachi has advised on one of these board but my beleif is that it has something to do with PCH rtc section.

[SMDFlea]

Re: Cmos reset works for 7-10 days only

Maybe changing the kb9012 will fix the problem as tomodachi said, its a strange problem.
The PCH,RTC,Crystlal could have something to do with it.

Just for reference,i watched a youtube video for a no pwer inspiron 3537-LA-9981P ,the kb9012 was put in place of a KB930QF A1 ,i don`t know if its pin to pin compatible,its not on any IC compatibility list i have. https://www.youtube.com/watch?v=2CueS2RanQM .

[caspian]

Re: Cmos reset works for 7-10 days only

is the 7-10-day period approximately constant?
how many times has this failure happened so far?

[mcplslg123]

Re: Cmos reset works for 7-10 days only

is the 7-10-day period approximately constant?
how many times has this failure happened so far?

yes, 7-10 days is almost constant . I've faced this issue on Lenovo AIO atlest 5 times in the last 3 months. On HP La-A992p i3 mb, i have similar experience.

I'm wondering whether none of you have faced this issue.

[caspian]

Re: Cmos reset works for 7-10 days only

if it is constant, it seems to be a periodic bios recovery or bios update which is done automatically by KBC or PCH. this is just a guess and I do not know more.

[mcplslg123]

Re: Cmos reset works for 7-10 days only

if it is constant, it seems to be a periodic bios recovery or bios update which is done automatically by KBC or PCH. this is just a guess and I do not know more.

There is no such phenomenon bro.

[SMDFlea]

Re: Cmos reset works for 7-10 days only

Did you check the cmos battery voltage when you took them out. Do you think it has anything to do with the crystal, the hp and dell have the samepart SLG3NB3375V. I looked for a datasheet ,couldn`t find one ,i looked at a different part just for reference

http://pdf1.alldatasheet.com/datashe...NT3342VTR.html

[mcplslg123]

Re: Cmos reset works for 7-10 days only

Did you check the cmos battery voltage when you took them out. Do you think it has anything to do with the crystal, the hp and dell have the samepart SLG3NB3375V. I looked for a datasheet ,couldn`t find one ,i looked at a different part just for reference

http://pdf1.alldatasheet.com/datashe...NT3342VTR.html

Cmos battery voltage was found ok at 3.06v. Crystal i have already replaced.

[tomodachi]

Re: Cmos reset works for 7-10 days only

Thanks tomodachi for your replies. I do have new kb9012. Will try soldering new kbc and program it. Lets see as it will work for 7-10 days anyways. So update only after 10 days.

Any other advice from senior members here??

Looking forward to receive your feedback, best of luck friend !

[mcplslg123]

Re: Cmos reset works for 7-10 days only

I replaced kb9012 as tomodachi suggested and put the old kbc dump into the new one. Delivered to customer on 20.06.2018 and it came back today with the very same symptoms-no display. Did a cmos reset-again display ok.

The only difference this time was a llittle bit more longer span before failing again. It worked for almost 30 days instead of usual 10-12 days.

Finally, i've given up on this as i cant understand what to do.

Thanks all for suggestions.

[piernov]

Re: Cmos reset works for 7-10 days only

RTC/CMOS circuit is mostly related to PCH so could be an issue with the PCH itself.