toshiba c850d black screen

[mo000]

hi
Toshiba C850D PLABX CSABX UMA DSC rev 2.1
builtin amd cpu
chipset amd
turning on with black screen and 0.9 amps consumption
all the voltages needed are present
i try flash bios with different files but same result
i suspect in cpu or chipset .

[mcplslg123]

Re: toshiba c850d black screen

Consumption on dc supply(after turning on)
01.With Ram stick
02.Without ram stick?

[mo000]

Re: toshiba c850d black screen

Consumption on dc supply(after turning on)
01.With Ram stick
02.Without ram stick?

almost a same consumption .

[mcplslg123]

Re: toshiba c850d black screen

That does mean ram is not read . Do check ram requirements,flash known good clean me bios as first steps.

[mo000]

Re: toshiba c850d black screen

That does mean ram is not read . Do check ram requirements,flash known good clean me bios as first steps.

but i have ram voltage 1.5v and vtt 0.75
can you clean to me the origin dump .
i can't fine any schematic for this model just a boardview .

[mcplslg123]

Re: toshiba c850d black screen

I think this one is amd apu-so no me region here.Its not enough to have 1.5V/0.75V for ram to work. One needs to check whether communication is there on SDA/SCL pins and Ram is being reset or not. You need a scope to check the communication.

[mo000]

Re: toshiba c850d black screen

I think this one is amd apu-so no me region here.Its not enough to have 1.5V/0.75V for ram to work. One needs to check whether communication is there on SDA/SCL pins and Ram is being reset or not. You need a scope to check the communication.

yes the cpu is amd apu
i check and found all ram requirements
VDD SPD = 3.3V
SDA/SCL =3.3v
DRAM_RST# = 1.5V
also i try a different ram and same result .

[mcplslg123]

Re: toshiba c850d black screen

Link the boardview here. have you checked ram slots full requirement? there should be a 3leg or 6 leg mosfet between FCH and ram slot for SDA/SCL communication. So there should be 2 such mosfets and take a close look on them.

[mo000]

Re: toshiba c850d black screen

Link the boardview here. have you checked ram slots full requirement? there should be a 3leg or 6 leg mosfet between FCH and ram slot for SDA/SCL communication. So there should be 2 such mosfets and take a close look on them.

according to the boardview SDA/SCL connection between fch and ram slot is direct no mosfets .
i think i check all requirements

VRef_DQ
VTT
VRef_CA
VDD SPD
SDA data
SCL clock
DRAM_RST#
all are ok nothing missing .

[piernov]

Re: toshiba c850d black screen

https://www.badcaps.net/forum/showthread.php?t=117483

If you request/offer BIOS/schematics/boardviews, please post in the appropriate subsection, and you can link to it in the troubleshooting topic.

[mcplslg123]

Re: toshiba c850d black screen

Yes,asper bdv nothing is inbetween ram slot /FCH wrt SMBUS comminication. Seems like FCH issue but cant say with 100% certainity without measurement pics on SDA/SCL/Dramrst# on scope.

[mo000]

Re: toshiba c850d black screen

Yes,asper bdv nothing is inbetween ram slot /FCH wrt SMBUS comminication. Seems like FCH issue but cant say with 100% certainity without measurement pics on SDA/SCL/Dramrst# on scope.

yes i think so
from ram slot under the scope
sda on pin 200 =3.3v
scl on pin 202 = 3.3
dramrt on pin 30 = 1.5
i think i get the right reading .

[mcplslg123]

Re: toshiba c850d black screen

yes i think so
from ram slot under the scope
sda on pin 200 =3.3v
scl on pin 202 = 3.3
dramrt on pin 30 = 1.5
i think i get the right reading .

These voltages are correct but that doesnt proves there is communication. That can be only confirmed by oscilloscope where you can observe the pulses.

[mo000]

Re: toshiba c850d black screen

These voltages are correct but that doesn't proves there is communication. That can be only confirmed by oscilloscope where you can observe the pulses.

yes i know but unfortunately i don't have oscilloscope .

[mon2]

Re: toshiba c850d black screen

If you power up without the ram, does the logic board send out the missing ram beep pattern?

[mo000]

Re: toshiba c850d black screen

If you power up without the ram, does the logic board send out the missing ram beep pattern?

no