ASUS ROG G751JM - self start and no VCORE and VGPU

**ktmmotocross** · 03-15-2019, 04:05 PM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

from this table of measured voltages looks like it all started from missing 1.05VS_PWRGD signal. so tomorrow i start from it

Attached Files

**piernov** · 03-15-2019, 04:16 PM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

No schematics for newer Asus. Last one available is UX31A2 AFAIK.
You're missing ALL_SYS_PWRGD so there's at least one S0 rail missing before VCore.

You measure 0V on +1.05VS_PWRGD so the issue is probably there. With the boardview check the voltage on output, input and enable signal of the +1.05VS regulator. Then mesure the resistance to ground on output of the regulator.

**ktmmotocross** · 03-16-2019, 05:44 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

have u guys anybody boardview for JM version? i have JY and it is completely differnet

**ktmmotocross** · 03-16-2019, 05:49 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

find almost everything on sulalaptop

**ktmmotocross** · 03-16-2019, 06:43 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

i have readings from U8200 and i have VIN and EN. but this TON looks like low to me. what do u thing after this reading?
resistance on 1.05V line is 76ohm

Attached Files

**piernov** · 03-16-2019, 07:28 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

I think TON is supposed to be somewhat low.
The regulator got input voltage and enable signal, but doesn't start switching at all. It is probably bad.
Do a visual inspection of the circuit around it to make sure the resistors aren't missing/damaged.

**ktmmotocross** · 03-16-2019, 07:52 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

Originally posted by piernov

I think TON is supposed to be somewhat low.
The regulator got input voltage and enable signal, but doesn't start switching at all. It is probably bad.
Do a visual inspection of the circuit around it to make sure the resistors aren't missing/damaged.

no missing or damged components find. try to find replacement for it

**ktmmotocross** · 03-16-2019, 08:52 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

no luck, dont have it on any board

anybody know intechange for RT8248A ?

**myth77** · 03-18-2019, 05:37 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

Check resistence to the ground on JP2603 and JP2604?

**ktmmotocross** · 03-18-2019, 06:55 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

96ohm

**ktmmotocross** · 04-13-2019, 06:00 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

replaced that ic but no luck. still the same.

i noticed that on PJP8201 and PJP8202 which is rail for 1.05V is resistance 96ohm, but when i attach charger it goes to 0ohm. try to isolate short, but when i desolder both PJP i get 0ohm on both side of it

**SMDFlea** · 04-13-2019, 07:31 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

Check jumpers PJ8203 ,PJ8202 and resistors PR8255 ,PR8256 and others in that area .

**ktmmotocross** · 04-14-2019, 12:47 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

do u have a schematic?

**SMDFlea** · 04-14-2019, 03:40 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

No, just boardview. PJ8203 and PJ8202 are interlayer,if you trace where they go you can see why you get 0ohm on both sides of PJP8201 and PJP8202

**ktmmotocross** · 04-14-2019, 03:50 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

i get 0 ohm only with power so there must be some switched power rail from 1.05 that is shorted. but im confused that when i remove both PJ still both side is shorted

**SMDFlea** · 04-14-2019, 04:47 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

What boardview software are you using ?

**SMDFlea** · 04-14-2019, 08:06 AM

Re: ASUS ROG G751JM - self start and no VCORE and VGPU

Originally posted by ktmmotocross

i get 0 ohm only with power so there must be some switched power rail from 1.05 that is shorted. but im confused that when i remove both PJ still both side is shorted

I think the short is around PR8255 and PR8256. You can see how PJP8201 and PJP8202 are connected,what pins 1 and 2 have in common.

Attached Files