SAMSUNG scala3 cpu core missing

[freeboxman]

hello,

I have a samsung laptop NP300E7A, after pushing the power button, nothing in screen and the fan spin full speed.

the issue started since putting admin and user password in the bios,
and also the cpu core was missing. I thought the bios was corrupted.

all power rails are good except the cpu core 0V, no short to ground in motherboard, the mosfets around the cpu IC showed 8 ohms to ground, but are good(tested outside motherboard with diode mode).

Before changing the CPU IC isl95831, i would like you to comment if there are other things to test

here are the voltages noted on the cpu IC. and diagram for scala3 14crv(i don't find a diagram for my laptop scala3-17 rev 1.3 BA41-01750A hst).

Thanks,

[Techtiger]

Re: SAMSUNG scala3 cpu core missing

hello,

I have a samsung laptop NP300E7A, after pushing the power button, nothing in screen and the fan spin full speed.

the issue started since putting admin and user password in the bios,
and also the cpu core was missing. I thought the bios was corrupted.

all power rails are good except the cpu core 0V, no short to ground in motherboard, the mosfets around the cpu IC showed 8 ohms to ground, but are good(tested outside motherboard with diode mode).

Before changing the CPU IC isl95831, i would like you to comment if there are other things to test

here are the voltages noted on the cpu IC. and diagram for scala3 14crv(i don't find a diagram for my laptop scala3-17 rev 1.3 BA41-01750A hst).

Thanks,

symptom may be a corrupted BIOS back up Old Bin & Flash BIOS

[freeboxman]

Re: SAMSUNG scala3 cpu core missing

symptom may be a corrupted BIOS back up Old Bin & Flash BIOS

Hello,

thank you for reply,

i have already to reflash bios, but nothing changed.

[mcplslg123]

Re: SAMSUNG scala3 cpu core missing

Ram resets?? Check DRAMRST on pin30 of ram slot. Without DRAMRST, core voltage will not come up. Measure the consumption of mb in the following two scenarios:
01. Turned on with ram
02.Turned on without ram.

[freeboxman]

Re: SAMSUNG scala3 cpu core missing

Ram resets?? Check DRAMRST on pin30 of ram slot. Without DRAMRST, core voltage will not come up. Measure the consumption of mb in the following two scenarios:
01. Turned on with ram
02.Turned on without ram.

Thank you for your help.

DRAMRST on pin 30 slot 1 or slot2, i have 0.0852V
Consumption with ram 0.2A, and without ram 0.19A~0.2A

Coil L3 Ram power i have 1.5V

i think the board is petronas, look like the same.

Thanks,

[mcplslg123]

Re: SAMSUNG scala3 cpu core missing

DRAMRST has to be 1.5V

[freeboxman]

Re: SAMSUNG scala3 cpu core missing

DRAMRST has to be 1.5V

Hello,

DRAMRST 1.5V comes from where? Q43?

[Techtiger]

Re: SAMSUNG scala3 cpu core missing

Hello,

DRAMRST 1.5V comes from where? Q43?

yes from Q43 you have to test all legs MCP1_DRAMRST_DRIVE# CHP3_DRAMRST_GATE

[freeboxman]

Re: SAMSUNG scala3 cpu core missing

yes from Q43 you have to test all legs MCP1_DRAMRST_DRIVE# CHP3_DRAMRST_GATE

Hello,

CHP3_DRAMRST_GATE i have 3.3V, but MCP1_DRAMRST_DRIVE# show 0.085V.
also MCP1_DRAMRST_DRIVE# come only from R393(other side of R393 connected to ground) and CPU pin R8 how can i test that pin?

all resistors and caps values are good around Q43.

thank you for your help.

[Techtiger]

Re: SAMSUNG scala3 cpu core missing

Find out R376 near the CPU both side voltage must be 1.5V if not there is another way but find out R376 first

[mcplslg123]

Re: SAMSUNG scala3 cpu core missing

You can remove Q43 and see if DRAMRST# reaches 1.5V on pin30 of ram slot.Wont do any harm.

[piernov]

Re: SAMSUNG scala3 cpu core missing

Is DRAMRST# even relevant when CPU VCore is missing?

[freeboxman]

Re: SAMSUNG scala3 cpu core missing

Hello Guys,

Sorry, i diden't find R376. the schematic seems not to be for the same model(my MB is scala3-17 and i can't find anything about that).

I removed Q43, and now i have 1.5V on pin 30 of ram slots , but nothing yet on cpu core coils 0V.


thank you,

[Techtiger]

Re: SAMSUNG scala3 cpu core missing

find out Q26out voltage for P1.05V_D try different BIOS fan spinning full speed is corrupted bios

[freeboxman]

Re: SAMSUNG scala3 cpu core missing

Hello,

the problem is solved. and the laptop working fine.

it was the Bios battery. however, I checked the voltage when I started my tests, I had 2.95V.

today, i changed the battery with a new one, and now i have 1.05V in cpu core voltage.


thank you all for your help.