Lenovo Yoga 500-14IBD backlight flickering

[comasutra]

Hi Friends,

Laptop works fine with power supply plugged in. On Battery with 80-100% charge also. When capacity is lower than 80% backlight begins flickering. Below 40-50% backlight turns off. Problem is motherboard-related - also testet with new battery.

Motherboard is LT41 MB 14217-1M

Any suggestions?

Thanks in advance.

Best regards.

[caspian]

Re: Lenovo Yoga 500-14IBD backlight flickering

this is the third time I hear this issue in this forum this year. If you search previous threads, you will find two other threads. those threads contain good recommendation on what to do.

[mcplslg123]

Re: Lenovo Yoga 500-14IBD backlight flickering

Did you tried another screen?? That should be the first step. It could happen due to glitch in display driver. Uninstall intel display driver and reboot to check if flickering goes away. Another option is to boot the pc in safe mode with network support. Open RUN and type msconfig. Go to services tab and uncheck "windows error reporting service + problem reports and solution. Reboot. Flickering goes away specially in win10 OS.

[comasutra]

Re: Lenovo Yoga 500-14IBD backlight flickering

this is the third time I hear this issue in this forum this year. If you search previous threads, you will find two other threads. those threads contain good recommendation on what to do.

I can't find any related threads.

Did you tried another screen?? That should be the first step. It could happen due to glitch in display driver....

Problem has nothing to do with screen or OS - Problem is in BIOS also.

[mcplslg123]

Re: Lenovo Yoga 500-14IBD backlight flickering

I can't find any related threads.



Problem has nothing to do with screen or OS - Problem is in BIOS also.

If you dont value other's advice, then why seek it. Solve it yourself.

[lordcroft]

Re: Lenovo Yoga 500-14IBD backlight flickering

I have sam problem, has there been a solution to the problem?

[teknikbursa]

Re: Lenovo Yoga 500-14IBD backlight flickering

pls check the 10 ohm resistor on vcc line of charge ic. if the resistor is not 10 ohm change it

[lordcroft]

Re: Lenovo Yoga 500-14IBD backlight flickering

pls check the 10 ohm resistor on vcc line of charge ic. if the resistor is not 10 ohm change it

In isl95520hrz, which is the vcc pin?

[teknikbursa]

Re: Lenovo Yoga 500-14IBD backlight flickering

I'm so sorry but my donor card is different than your card but anyway pls check the resistors around charger ic specially acin line

[caspian]

Re: Lenovo Yoga 500-14IBD backlight flickering

this is the third time I hear this issue in this forum this year. If you search previous threads, you will find two other threads. those threads contain good recommendation on what to do.

I found those threads:
https://www.badcaps.net/forum/showthread.php?t=76823
https://www.badcaps.net/forum/showthread.php?t=31354

[odemontealto]

Re: Lenovo Yoga 500-14IBD backlight flickering

Hi. I have received a Lenovo Yoga 500-14IBD with a flickering problem when it is running in battery mode.

When in battery mode, the DCBATOUT_LCD voltage ranges from 7.5 to 7.8v. When it is at 7.5v there is a flickering of the backlight. With 7.8v the flickering disappears. If it is with the charger connected DCBATOUT_LCD is 19v. All Ok.

In the diagram we can see the backlight voltage in battery mode is 10v. If we only have 7.5-7.8v, problems ...



Who is responsible for supplying 10v in battery mode (remember, battery is only 7.4v.)? Well, a step up circuit governed by an RT8509GQW that apparently is not doing its job.



Yoga 500-14 IBD Scheme:

[silvake]

Re: Lenovo Yoga 500-14IBD backlight flickering

Well... what if all this boost regulator circuit is totally missing from the board in some versions?

I'm trying to fix another Yoga 500-14IBD with the exact problem as discusssed here.
The screen flickers like hell when you disconnect the charger... not only in Windows, but in BIOS screen as well (so drivers or other software issues are out of the question).

This model is also powered by a 2-cell battery pack which appears to be in pretty decent shape, measured with a professional battery tester it's still rated at about 75% of its original capacity.

I tested the above theory and indeed, manually feeding some 7.6 Volts or more with a lab-psu on the DCBATOUT_LCD line, instantly stops the flickering.

I wanted to check the boost converter as (logically) suggested here, but I noticed my board is different, it doesn't even have this LCD voltage regulator.. the PU5001 (RT8509 IC) and all related components were not even placed on the board.
I guess Lenovo tried to cut down the costs and hoped a voltage level of about 7.2-7.4V shoud be enough to power the LCD backlight on battery... but it seems they were wrong.

Is it possible that this board's model was specifically designed to work well only with a 3-cell battery?
I'm wondering if a higher voltage of 11.1V (or at least 9.3-9.6V when discharged), feeded on the DCBATOUT_LCD line by such a battery, might solve the issue.

Any thoughts or advice?

[tesnic]

Re: Lenovo Yoga 500-14IBD backlight flickering

In isl95520hrz, which is the vcc pin?

Hi guys! I have t'he same qüestión, im not capable to localize it into a yoga 500-14ibd that dont charge t'he battery
Thanks

[tesnic]

Re: Lenovo Yoga 500-14IBD backlight flickering

To add some information. My Yoga 500-14ibd works only with AC adapter. T'he (New) battery dont charge. When i plug the charger, no voltage or amper movements. Im reviewing t'he resistors above t'he ISL95520HRZ but im not capable to localize t'he problem. All mosfets are OK. Thanks in advance.