lenovo Yoga 910-13IKB black screen

[rascao]

Hello friends, i have a lenovo Yoga 910-13IKB when you turn on the led come on but the screen remain black no backlight nothing, the motherboard charge the batery, and i can find almost all the power lines in the on state, cpu, ran 3v 8v is the main one even with the charger plugin, 5 v, but the GFX power line remain 0, i check for short but on the multimeter give me the sound of a short but is like the CPU when is not energized the line is on short so no good info, i check the power schematics for the GFX and it have 2 "AOZ5029Q" for the job and they are not short and they are working because i exchange 1 from the gfx to the CPU and the cpu start to send Volts whit the replaced one, so the AOZ5029Q are working, i check the lines

the 5v ios present and the 8v, i ges the gate is the PWM_GT2 FCCM_GT? and they have 2.3 v so there is working, but is not working so i dont know what else try

It maybe is the on board ran that is bad? and if the ran is not good it will not energize the gfx power line? i upload the schematics and hope any one can help me whit this

[emestee]

Re: lenovo Yoga 910-13IKB black screen

Please identify the board correctly and post schematics.

I dont think there should be anything like 8V anywhere on the board.

GPU power up is nearly the last stage of the power sequence and you should be speculating about the stage before that failing.



To measure low resistance rails, use ohm mode and not diode mode.

[rascao]

Re: lenovo Yoga 910-13IKB black screen

Please identify the board correctly and post schematics.
I dont think there should be anything like 8V anywhere on the board.
GPU power up is nearly the last stage of the power sequence and you should be speculating about the stage before that failing.
To measure low resistance rails, use ohm mode and not diode mode.

sorry didn't pres upload on the schematic, here it is, https://www.badcaps.net/forum/showthread.php?t=122737 and the board is CYG50 NM-A901 Agera-SVT rev 1.0, in the input of the charger there is 20v, after the first big coil it get 8v, the same 8 v from the battery is rated to 7.6v, if i remove the battery the rail remain as 8v, i did use the ohm is 10 OHMS from the gfx coils and 12 ohms from the cpu coil

[emestee]

Re: lenovo Yoga 910-13IKB black screen

What do you mean first big coil? The 20V rail has no coils on it. After the initial switching mechanism, it is distributed to secondary power supplies, none of whom should be accepting or producing 8V. So whatever coil you're measuring at isn't 20V and, more importantly, there is not and can not be anything like 8V anywhere on the board. You are looking at a fault. Please identify the coil.

You need to test every rail, not just the cpu and graphics ones.

[rascao]

Re: lenovo Yoga 910-13IKB black screen

PL12 is the coil i refer to big coil, is goin to the charging circuit and the main Vrail is what i see here, the battery is a 7,6 v rated one so for charging i think it is the 8v, that's why i think this motherboard uses the 8v as the main V rail because i see everywhere on the power circuits the 8v, that's why i think it was normal on this mother board as the VIN on PU25 PU29 and PU24 are 8v

pd thanks for your time helping out

[emestee]

Re: lenovo Yoga 910-13IKB black screen

I see what you mean. Is this a netpad or some other miniature laptop? Having 8v for VIN would be a very.. unorthodox approach. I still dont think this would normally be the case, but I guess everything is possible.

If 8V is the correct voltage, and the machine stops initializing before the graphic core is powered up, that's the part of the initialization sequence you will have to look at. I'd begin with standard RTC battery, oscillators, and coil resistance checks.

[rascao]

Re: lenovo Yoga 910-13IKB black screen

I see what you mean. Is this a netpad or some other miniature laptop? Having 8v for VIN would be a very.. unorthodox approach. I still dont think this would normally be the case, but I guess everything is possible.

If 8V is the correct voltage, and the machine stops initializing before the graphic core is powered up, that's the part of the initialization sequence you will have to look at. I'd begin with standard RTC battery, oscillators, and coil resistance checks.

the laptop is not as mini as you can imagine



i will check that thing you are telling me thanks, i check the battery and is in good health, i take out the coils and they seems fine with the resistance as they should be.

Is there any way the memory is not working and because of that the gfx is not initializing? because the ran is getting his volts, on the schematics i cant find the on sequence to be sure , and i don't find the BOARDVIEW for this model

[emestee]

Re: lenovo Yoga 910-13IKB black screen

It's possible, yes. You can test the RAM by measuring the 3.3, 1.5/1.35 and the reference voltage that's half of the 1.5/1.35 one. Don't forget to look at the power ok and enable signals.

[rascao]

Re: lenovo Yoga 910-13IKB black screen

It's possible, yes. You can test the RAM by measuring the 3.3, 1.5/1.35 and the reference voltage that's half of the 1.5/1.35 one. Don't forget to look at the power ok and enable signals.

thanks for your help, i am a noob on this i will investigate how to thes the power ok and enable siglas thanks!

[mcplslg123]

Re: lenovo Yoga 910-13IKB black screen

That 8V as main rail doesnt seems correct to me. What is the voltage on pin1/4/5 of DC-IN mosfets??

[piernov]

Re: lenovo Yoga 910-13IKB black screen

Buck-boost NVDC topology, main power rail is taken from battery charging rail (after buck-boost converter), so it's normal to have a voltage close to battery voltage.

[emestee]

Re: lenovo Yoga 910-13IKB black screen

Buck-boost NVDC topology, main power rail is taken from battery charging rail (after buck-boost converter), so it's normal to have a voltage close to battery voltage.

This is why you're the grandmaster in these parts...

[rascao]

Re: lenovo Yoga 910-13IKB black screen

That 8V as main rail doesnt seems correct to me. What is the voltage on pin1/4/5 of DC-IN mosfets??

on the output of PQ15 and PQ16 i have 8.7 vots no battery connected just charger, and on the PQ10 and PQ11 i have 20v

[openminded]

Re: lenovo Yoga 910-13IKB black screen

on the output of PQ15 and PQ16 i have 8.7 vots no battery connected just charger, and on the PQ10 and PQ11 i have 20v

I have the same issue and measurements. Any tips?
The isl 927 ?

[openminded]

Re: lenovo Yoga 910-13IKB black screen

I shorted PQ15 because I thought it was missing the gat signal, now I got 5.1 V instead of 20...